The post explains a 3 powerful yet simple sine wave 12V inverter circuits using a single IC SG 3525. The first circuit is equipped with a low battery detection and cut off feature, and an automatic output voltage regulation feature.
This circuit was requested by one of the interested readers of this blog. Let's learn more about the request and the circuit functioning.
Design#1: Basic Modified Sine
In one of the earlier posts I discussed the pin out functioning of the IC 3525, using the data, I designed the following circuit which is though quite standard in its configuration, includes a low battery shut down feature and also an automatic output regulation enhancement.
The following explanation will walk us through the various stages of the circuit, let's learn them:
As can be witnessed in the given diagram, the IC SG3525 is rigged in its standard PWM generator/oscillator mode where the frequency of oscillation is determined by C1, R2 and P1.
P1 can be adjusted for acquiring accurate frequencies as per the required specs of the application.
The range of P1 is from 100Hz to 500 kHz, here we are interested in the 100 Hz value which ultimately provides a 50Hz across the two outputs at pin#11 and Pin#14.
The above two outputs oscillate alternately in a push pull manner (totem pole), driving the connected mosfets into saturation at the fixed frequency - 50 Hz.
The mosfets in response, "push and Pull the battery voltage/current across the two winding of the transformer which in turn generates the required mains AC at the output winding of the transformer.
The peak voltage generated at the output would be anywhere around 300 Volts which must adjusted to around 220V RMS using a good quality RMS meter and by adjusting P2.
P2 actually adjusts the width of the pulses at pin#11/#14, which helps to provide the required RMS at the output.
This feature facilitates a PWM controlled modified sine waveform at the output.
Automatic Output Voltage Regulation Feature
Since the IC facilitates a PWM control pin-out this pin-out can be exploited for enabling an automatic output regulation of the system.
Pin#2 is the sensing input of the internal built in error Opamp, normally the voltage at this pin (non inv.) should not increase above the 5.1V mark by default, because the inv pin#1 is fixed at 5.1V internally.
As long as pin#2 is within the specified voltage limit, the PWM correction feature stays inactive, however the moment the voltage at pin#2 tends to rise above 5.1V the output pulses are subsequently narrowed down in an attempt to correct and balance the output voltage accordingly.
A small sensing transformer TR2 is used here for acquiring a sample voltage of the output, this voltage is appropriately rectified and fed to pin#2 of the IC1.
P3 is set such that the fed voltage stays well below the 5.1V limit when the output voltage RMS is around 220V. This sets up the auto regulation feature of the circuit.
Now if due to any reason the output voltage tends to rise above the set value, the PWM correction feature activates and the voltage gets reduced.
Ideally P3 should be set such that the output voltage RMS is fixed at 250V.
So if the above voltage drops below 250V, the PWM correction will try to pull it upward, and vice versa, this will help to acquire a two way regulation of the output,
A careful investigation will show that the inclusion of R3, R4, P2 are meaningless, these may be removed from the circuit. P3 may be solely used for getting the intended PWM control at the output.
Low Battery Cut-of Feature
The other handy feature of this circuit is the low battery cut off ability.
Again this introduction becomes possible due to the in built shut down feature of the IC SG3525.
Pin#10 of the IC will respond to a positive signal and will shut down the output until the signal is inhibited.
A 741 opamp here functions as the low voltage detector.
P5 should be set such that the output of 741 remains at logic low as long as the battery voltage is above the low voltage threshold, this may be 11.5V. 11V or 10.5 as preferred by the user, ideally it shouldn't be less than 11V.
Once this is set, if the battery voltage tends to go below the low voltage mark, the output of the IC instantly becomes high, activating the shut down feature of IC1, inhibiting any further loss of battery voltage.
The feedback resistor R9 and P4 makes sure the position stays latched even if the battery voltage tends to rise back to some higher levels after the shut down operation is activated.
Parts List
All resistors are 1/4 watt 1% MFR. unless otherwise stated.
- R1, R7 = 22 Ohms
- R2, R4, R8, R10 = 1K
- R3 = 4K7
- R5, R6 = 100 Ohms
- R9 = 100K
- C1 = 0.1uF/50V MKT
- C2, C3, C4, C5 = 100nF
- C6, C7 = 4.7uF/25V
- P1 = 330K preset
- P2---P5 = 10K presets
- T1, T2 = IRF540N
- D1----D6 = 1N4007
- IC1 = SG 3525
- IC2 = LM741
- TR1 = 8-0-8V.....current as per requirement
- TR2 = 0-9V/100mA Battery = 12V/25 to 100 AH
The low battery opamp stage in the above shown schematic could be modified for a better response as given in the following diagram:
Here we can see that pin3 of the opamp now has it's own reference network using D6 and R11, and does not depend on the reference voltage from the IC 3525 pin16.
Pin6 of the opamp employs a zener diode in order to stop any leakages that might disturb pin10 of the SG3525 during its normal operations.
R11 = 10K
D6, D7 = zener diodes, 3.3V, 1/2 watt
Another Design with Automatic Output Feedback Correction
Circuit Design#2:
In the above section we learned the basic version of IC SG3525 designed to produce a modified sine wave output when used in an inverter topology, and this basic design cannot be enhanced to produce a pure sinewave waveform in its typical format.
Although the modified squarewave or sinewave output could be OK with its RMS property and reasonably suitable for powering most electronic equipment, it can never match the quality of a pure sinewave inverter output.
Here we are going to learn a simple method which could be used for enhancing any standard SG3525 inverter circuit into a pure sinewave counterpart.
For the proposed enhancement the basic SG3525 inverter could be any standard SG3525 inverter design configured to produce an modified PWM output. This section is not crucial and any preferred variant could be selected (you can find plenty online with minor differences).
I have discussed a comprehensive article regarding how to convert a square wave inverter to a sinewave inverter in one of my earlier posts, here we apply the same principle for the upgrade.
How the Conversion from Squarewave to Sinewave Happens
You might be curious to know regarding what exactly happens in the process of the conversion which transforms the output into a pure sinewave suitable for all sensitive electronic loads.
It is basically done by optimizing the sharp rising and falling square wave pulses into a gently rising and falling waveform. This is executed by chopping or breaking the exiting square waves into number of uniform pieces.
In the actual sinewave, the waveform is created through an exponential rise and fall pattern where the sinusoidal wave gradually ascend and descend in the course of its cycles.
In the proposed idea, the waveform is not executed in an exponential, rather the square waves are chopped into pieces which ultimately takes the shape of a sinewave after some filtration.
The "chopping" is done by feeding a calculated PWM to the gates of the FET via a BJT buffer stage.
A typical circuit design for converting the SG3525 waveform into a pure sinewave waveform is shown below. This design is actually an universal design which may be implemented for upgrading all square wave inverters into sinewave inverters.
As may be in the above diagram, the lower two diodes are connected to a PWM feed or input, which causes the transistors to switch according to the PWM ON/OFF duty cycles.
This in turn rapidly chop the 50Hz pulses at the bases of the BC547/BC557 coming from the SG3525 output pins.
The above operation ultimately force the mosfets also to turn ON and OFF in the same pattern as the SPWM for each of the 50/60Hz cycles. This SPWM is then induced into the transformer primary by the MOSFETs, consequently producing a sine waveform at the output or the secondary side of the transformer.
If an ordinary PWM is used as explained below, then its frequency should be 4 times more than the base 50 or 60 Hz frequency. so that each 50/60Hz cycles are broken into 4 or 5 pieces and not more than this, which could otherwise give rise to unwanted harmonics and mosfet heating.
PWM Circuit
The PWM input feed for the above explained design can be acquired by using any standard IC 555 astable design as shown below:
This IC 555 based PWM circuit can be used for feeding an optimized PWM to the bases of the BC547 transistors in the first design such that the output from the SG3525 inverter circuit acquires an RMS value close to mains pure sinewave waveform RMS value.
Using an SPWM
Although the above explained concept would greatly improve the square wave modified output of a typical SG3525 inverter circuit, an even better approach could be to go for an SPWM generator circuit.
In this concept the "chopping" of each of the square wave pulses is implemented through a proportionately varying PWM duty cycles rather than a fixed duty cycle.
I have already discussed how to generate SPWM using opamp, the same theory may be used for feeding the driver stage of any square wave inverter.
A simple circuit for generating SPWM can be seen below:
Using IC 741 for Processing SPWM
In this design we see a standard IC 741 opamp whose input pins are configured with a couple of triangle wave sources, one being much faster in frequency than the other.
The triangle waves could be manufactured from a standard IC 556 based circuit, wired as an astable and compactor, as shown below:
#UPDATE: The above "slow triangle waves" can be directly acquired from the Ct pin of the IC, that means you can now eliminate or ignore the above IC 555 stage for the slow triangle waves.
As can be seen in the above two images, the fast triangle waves are achieved from an ordinary IC 555 astable.
However, the slow triangle waves are acquired through an IC 555 wired like a "square wave to triangle wave generator".
The square waves or the rectangular waves are acquired from pin#4 of SG3525. This is important as it synchronizes the op amp 741 output perfectly with the 50 Hz frequency of the SG3525 circuit. This in turn creates correctly dimensioned SPWM sets across the two MOSFET channels.
When this optimized PWM is fed to the first circuit design causes the output from the transformer to produce a further improved and gentle sine waveform having properties much identical to a standard AC mains sine waveform.
However even for an SPWM, the RMS value will need to be correctly set initially in order to produce the correct voltage output at the output of the transformer.
Once implemented one can expect a real sinewave equivalent output from any SG3525 inverter design or may be from any square wave inverter model.
If you have more doubts regarding SG3525 pure sinewave inverter circuit you can feel free to express them through your comments.
UPDATE
A basic example design of a SG3525 oscillator stage can be seen below, this design could be integrated with the above explained PWM sinewave BJT/mosfet stage for getting the required enhanced version of the SG3525 design:
Complete circuit diagram and PCB layout for the proposed SG3525 pure sine wave inverter circuit.
Courtesy: Ainsworth Lynch
Design#3: 3kva Inverter circuit using the IC SG3525
In the previous paragraphs we have comprehensively discussed regarding how an SG3525 design could be converted into an efficient sinewave design, now let's discuss how a simple 2kva inverter circuit can be constructed using the IC SG3525, which can be easily upgraded to sinewave 10kva by increasing the battery, mosfet and the transformer specs.
The basic circuit is as per the design submitted by Mr. Anas Ahmad.
The explanation regarding the proposed SG3525 2kva inverter circuit can be understood from the following discussion:
hello swagatam, i constructed the following 3kva 24V inverter modified sine wave (i used 20 mosfet with resistor attached to each, moreover i used center tap transformer and i used SG3525 for oscillator).. now i want to convert it to pure sine wave, please how can i do that?
Basic Schematic
My Reply:
Hello Anas,
first try the basic set up as explained in this SG3525 inverter article, if everything goes well, after that you can try connecting more mosfets in parallel.....
the inverter shown in the above daigram is a basic square wave design, in order to convert it to sine wave you must follow the steps explained below The mosfet gate/resistor ends must be configured with a BJT stage and the 555 IC PWM should be connected as indicated in the following diagram:
Regarding Connecting parallel mosfets
ok, i have 20 mosfet(10 on lead A, 10 on lead B), so i must attached 2 BJT to each mosfet, that's 40 BJT, and likewise i must connect only 2 BJT coming out from PWM in parallel to the 40 BJT? Sorry am novice just trying to pick up.
Answer:
No, each emitter junction of the respective BJT pair will hold 10 mosfets...therefore you will need only 4 BJTs in all....
Using BJTs as Buffers
1. ok if i may get you right, since you said 4 BJTs, 2 on lead A, 2 on lead B, THEN another 2 BJT from the output of PWM, right?
2. am using 24 volt battery hope no any modification to the BJT collector terminal to the battery?
3. i have to use variable resistor From oscillator to control the input voltage to the mosfet, but i don't know how i will go about the voltage that will go to the base of the BJT in this case, what will i do so that i want end up blow up the BJT?
Yes, NPN/PNP BJTs for the buffer stage, and two NPN with the PWM driver.
24V will not harm the BJT buffers, but make sure to use a 7812 for stepping it down to 12V for the SG3525 and the IC 555 stages.
You can use the IC 555 pot for adjusting the output voltage from the trafo and set it to 220V. remember your transformer must be rated lower than the battery voltage for getting optimum voltage at the output. if your battery is 24V you can use an 18-0-18V trafo.
Parts List
IC SG3525 Circuit
all resistors 1/4 watt 5% CFR unless otherwise specified
10K - 6nos
150K - 1no
470 ohm - 1no
presets 22K - 1no
preset 47K - 1no
Capacitors
0.1uF Ceramic - 1no
IC = SG3525
Mosfet/BJT Stage
All mosfets - IRF540 or any equivalent Gate resistors - 10 Ohms 1/4 watt (recommended)
All NPN BJTs are = BC547
All PNP BJTs are = BC557
Base Resistors are all 10K - 4nos
IC 555 PWM Stage
1K = 1no 100K pot - 1no
1N4148 Diode = 2nos
Capacitors 0.1uF Ceramic - 1no
10nF Ceramic - 1no
Miscellaneous IC 7812 - 1no
Battery - 12V 0r 24V 100AH Transformer as per specs.
A Simpler Alternative
Khumbulani says
Hlw sir what is the value of pin number 8 in that circut of 3kva circuit
Swagatam says
Pin#8 capacitor is for initiating a soft start at the output of the inverter. You can use any capacitor between 0.1uF and 1uF
Seun says
Good day Sir, Chief Swag, please can op amp voltage follower do the work of btj buffer stage of the oscillator?
Swagatam says
Yes op amp voltage follower can be used instead of the BJT buffer.
Seun says
Thanks so much Swagatam for your reply, please my concern is how to protect this in case of positive and negative line bridging.
Without buffer stage, bridge does not damage the inverter.
However, buffer stage is essential.
Thanks Swag.
Swagatam says
Hello Seun,
Buffer stage is not essential. If you are referring to a SG3525 circuit you can connect the mosfets directly with the output pins.
I did not understand what you want you protect? If you short circuit a battery only a fuse can protect the battery.
Neybero says
There is something else that I need to understand. In other inverter drawing I have seen resisitance and diodes connected to gate of mosfet for protection. Is there any unprotection comparing your schematic with the one that use those diodes?
Swagatam says
Yes, the diode across the gate resistance facilitates better and efficient conduction of the MOSFETs and lower heating of the MOSFETs.
Neybero says
Hi Swagatam, in my country we use 60Hz apliances. Regarding the first and second schematic, by P1 can I set 60Hz and use it without operation problem.
Is there something else to be minded if I increase number of mostfet to get more power?
Swagatam says
Hi Neybero,
I would recommend you the following circuit instead, since it is a simpler one and has been tested. You can tweak the R1/C1 values to get the required 60 Hz output
https://www.homemade-circuits.com/wp-content/uploads/2019/04/feedback-1024×460.png.webp
Neybero says
Thank you for responding. As electronic hobbilist I am not experience in electronic design.
To be sure. For frequency you say R1-C1, is it right or R2-C1, R1-C4?.
I am sorry if I bother you with my unexperience.
Swagatam says
Only R1 and C1 are responsible for the output frequency of the inverter and only these must be adjusted.
Ekoe Anthony says
Hello Swagatam,
Please I have seen an inverter designed as PWM module from the internet, and this is not from your posts, using the Sg3525 IC.
It has this features, Overload protection, low battery shut down, automatic cooling fan. This is only, the oscillation board, with each pin of these functions out.
Since you said we could bring to you at times some of these to discuss, I would like to know where to in the circuit when I am adding a transformer 50hz and power mosfets to complete the design, I should connect the overload pin and low battery shut down pin.
Swagatam says
Hello Ekoe,
Please refer to the first circuit from the above article, and connect the mosfets and the transformer exactly as shown the diagram.
APURV DEEPAK says
Hello sir..I want to made this project can you tell me which circuit suitable for me with output voltage feedback.. and any modification will required or not.
Swagatam says
Hello Apurv,
All the circuits are good, but you can specifically try the following design with a feedback:
https://www.homemade-circuits.com/wp-content/uploads/2019/04/feedback-1024×460.png.webp
APURV DEEPAK says
Ok sir.one more question is that if added mosfet driver (totempole driver) in pin 11 and 14 for increasing the output current to drive more mosfet .then any modification will happen in your given cricuit or not…
According your CT,RT,RD value is given in your cricuit digram by the formula(1/CT(0.7Rt +3Rd).I calculated then coming frequency is 94khz but my requirement is 50hz how it can be occurred..
Please clear my all point thank you..
Swagatam says
Hello Apurva,
Driver is not required for adding MOSFETs in parallel, you can add the MOSFETs in parallel directly with the pin#11 and pin#14 of the IC. No modifications will be required.
In the formula did you convert microfarad into Farad? You will have to convert microfarad into farad for getting the correct results.
If the formula is not giving proper results then it is better to confirm the frequency practically using a frequency meter.
APURV DEEPAK says
Yes sir I firstly converted into farad then i calculated it but the result came same (94643hz).so please give me a correct value of CT,Rt and Rd which I can used in my project because it’s my college project for demonstration purpose.and one more question is that if I can used mosfet driver cricuit then I think no any problem will create.if I am right.
Thank you and waiting for your response..
Swagatam says
Hi, Apurv,
your calculations are correct. So I will suggest you to please try increasing the RT value until you get the approximate 50 Hz frequency.
It can be difficult for me to do the calculations for you due to lack of time.
APURV DEEPAK says
Hello sir, in my calculation I used CT,RT,Rd is(0.1uf, 150k (100k preset and 50k Resistance) ,47ohm) when i set into the 133k the total frequency is 104hz comes out after calculation.so please verify my it’s correct or not and one more thing also I want know that the pin #11 and pin#14 their total sum frequency will be calculated or not. because the frequency perivouslly I measured is total frequency.
So please rply me sir…I working on this project
Swagatam says
Apurv, as I told you before due to lack of time I cannot confirm the calculations. You can confirm it by testing the real results with a meter.
One half cycle from pin#11 and one half cycle from pin#14 constitutes one full cycle of the output frequency of the inverter. You can measure the 50 Hz frequency by attaching the meter probes across pin#11 or pin#14 and ground. Or you can connect the meter probes across pin#11 and pin#14 to check the 50 Hz frequency.
APURV DEEPAK says
Your rply is important for me sir.if you can do immediately then I work on project very smoothly perfectly so please rply me sir….
Swagatam says
Apurv, I am not always online, therefore my replies can be within 1 hour or sometimes 12 hours.
APURV DEEPAK says
Hello sir I requested to you please concern my msg and immediate reply me…thank you
APURV DEEPAK says
Hello sir please reply my comments..I am waiting your answer.
Gabriel says
Dear swagatam. Thanks for the good works you are doing on this space.
I designed a 24v 1.5kva H-Bridge inverter using SG3524.
So far it is working fine.
I have used a pressing iron of 1200watts on it and it operates fine.
My challenge is on inductive loads. My freezer of 120watts couldn’t start on it.
It works on my fan but it’s giving off a humming sound and it doesn’t run on full power.
I guessed it is because of the inverter being a modified sinewave.
How can I eliminate this problem?
Would putting a capacitor of say 1uf or 1.5uf at the output of the inverter help?
Any idea on what to do?
Swagatam says
That’s wonderful Gabriel, Glad you could build a full bridge inverter successfully.
Freezer might require high current during initial switch ON loading. A 120 watt unit could consume around 400 watts at the start. That is why your inverter might be having difficulty in handling the freezer. You can try upgrading your inverter to 600 watts and then check the results.
Yes you can add a 3uF/400V capacitor across the output terminals of the inverter in order to reduce the noise to some extent.
SG3524 inverters are normally square wave inverters so tackling the noise may not be easy.
Ngwabe says
Hullo friend I have fridge it’s lebled 150watts but have tried an invert of 600watts but it doesn’t work can you advice me the circuit that can start it. Thanks
Swagatam says
Hi, if you built the 600 watt inverter correctly then it should be able to operate the 150 watt inverter with ease.
Your inverter might not be actually rated at 600 watts.
Adilson says
good morning, I would like to know if this circuit for sine wave air to use in an inverter that does not use an iron transformer, so used in a high frequency inverter in the first stage and a bridge – H in the second stage?? I’ve been reading your post, and I want to thank you for making your knowledge available!!!
Swagatam says
Hi, this circuit can be customized for a ferrite based transformer by increasing the oscillator and PWM frequency to many kHz. However, the designing of the ferrite core transformer would be crucial and will need to be done with a lot of calculations.
I am glad you are finding my posts helpful.
Anthony says
Thanks Mr Swagatam for the reply.
Ekoe Anthony says
Good morning Swagatam,
I’ve built almost your sg3525 design from this post, the simple ones, only inverter number 1 and 2, I couldn’t build that I’ve found complex very little.
Now about the design number 1, the first from this post, the i.c lm371 for the low battery circuit, pin#7 of the circuit are not connected to the whole system. Please, where do they go to the inverter circuit if I would try to build this. Please where do these two pins connect to?
Swagatam says
Hello Ekoe,
The low battery cut off op amp is a 741 IC. The pin 7 and pin 4 are its supply voltage pins which will need to be connected with the battery supply if the battery is a 12V battery. Pin7 will go to the (+) of the battery, and pin4 to the (-) of the battery
Anthony says
Hello Swagatam,
I’ve decided to use my inverter project build in their square wave form, your design, sg3525 3kva and the sg3525 5000watts square wave. And I wish to use these two mosfets, irf 3205 and irfz 44n, which are common at my place and affordable. Do I need any change of the gate resistances ? If so, which of them do I have to look for, for the two inverters of your design, please. My fundamental knowledge in electronic is few so often my questions.
Swagatam says
Hello Anthony,
You can try the 3rd circuit from top. It is simple and compact. Build with a single mosfet first. If you succeed with it, then you can add more number mosfets in parallel to increase its wattage.
Anthony says
Hello Swagatam,
Thanks for the reminder of the oscilloscope, now I built the Spwm, the fast triangle waves your design, with the Ne555 i.c.
Adjusting the preset 50k, I got the
400hz as you indicated in your posts after my persistent trials.
Please did say if I connect I suppose to still get my 50hz oscillating normally from pin #11 and #14 that will drive the power mosfets?
Swagatam says
Hello Anthony,
As mentioned earlier, to proceed with the SPWM section you must have the following two things with you:
1) A basic SG3525 inverter producing 220V AC output at 60 watt or more
2) An oscilloscope to check the waveform.
Without these two you cannot verify the SPWM stage
Anthony says
Hello Swagatam, I have built the basic square wave of sg3525 already. It’s just unfortunate that I don’t have the oscilloscope. Thanks for your advice.
Swagatam says
Hello Anthony, the inverter should be complete and produce 220V output and able to illuminate a 60 watt lamp. oscilloscope will be required for the SPWM integration.
Anthony says
Hello Swagatam,
Please may I suggest if you could demonstrate some of the sg3525 inverter circuit to us through a video in the YouTube.
Swagatam says
I had built and tested this circuit long back about 10 years ago, and it worked perfectly for me. It won’t be possible for me to build it again and make a video, that will be a lot of hard work.
If you are finding the circuit difficult then you should first try the basic square wave SG3525 circuit and then upgrade it into a sine wave inverter step by step.
You must have a small oscilloscope to test the waveform otherwise building the inverter correctly may not be possible.
Anthony says
Hello Swagatam,
Do I need any polirise capacitor on the battery positive line going to the Power regulator ic 7812 which feeds the main oscillator i.c Sg3525 of the inverter circuit. If so which value do you recommend to me.
Secondly the two diodes of the PWM were turned upside down, could please explain to me why. I know diode has only one passage . Please thanks.
Swagatam says
Hello Anthony,
you can use a polarized capacitor before and after 7812. You can use a 100uF/50V capacitor. The diodes pull down the transistor bases to 0V for all the 0V pulses of the PWM cycle, in this way it forces the transistors to switch ON/OFF exactly in accordance with the PWM pulses.
Anthony says
Please Swagatam, again I didn’t connect my shut down line from pin #10, what will happen to my inverter if I don’t do so. The role of the feed back? Is not added to the sg3525 of 3kva inverter circuit.
Swagatam says
You can keep the pin#10 connected to ground initially. Feedback (220V constant output) can be added only when the basic inverter circuit works correctly.
Anthony says
Hello Engineer,
My final struggle and the results, I finally finished the oscillation board, setting my preset 47K, I got 03.80volts d.c. and 50hz at the two pins 11&14.
Setting up the preset 22K, I increase the d.c voltage at the two oscillations to 05.08&05.07 each.
I build the PWM circuit and the frequency I got was 247.7Hz.
Connecting the two overheat all the BJT transistors on the oscillation lines. And result is giving negative 200-300mv d.c and unstable, there I was afraid to destroy my transistors, I did not connect any of my power transistors. I used the conversion design with the two 10K and 547.
Thanks that you at last replaced it with the two diodes.
What suppose to be the d. c voltage that would drive the power transistors if all the circuit is set and also the oscillator frequency if the PWM is connected?
Swagatam says
Hello Anthony,
Do not use the PWM initially. First build the basic SG3525 inverter and test the results. If you get 220V AC perfectly from this inverter only then proceed with the PWM.
If you try to build the whole circuit all at once then you may face serious problems. You must build the circuit stage-wise.
And please remember without an oscilloscope you cannot succeed with the PWM integration.
Anthony says
Thanks Swagatam, Please the design circuit that convert the sg3525 into a sine wave, one has two transistors 547 and at each base is connected 10k ohms resistors, another you put recently has only two diodes 1N 4148 in the inverse way. Which of the two should be applied for the conversion stage. Thanks
Swagatam says
Hello Anthony,
The design using two BC547 could not be used for SPWM that is why I changed the previous diagram with a new diagram which has two diodes instead of two transistors. This new design with two 1N4148 diodes can be used universally with ordinary PWM and also with SPWM
Anthony says
Hello Good morning, Please how do I connect the shut down line from pin#10 of the sg3525 3kva design. Is it going to be used as switch between battery plus and minus in the circuit or how please direct me.
Swagatam says
If you are not using an automatic feedback for the shut down then you can keep the pin#10 connected with the ground line. This will keep the shut down feature disabled.
Anthony says
Hello Mr Swagatam, thanks for alerting me, I waisted my energy all this while. Okay I am building your 3kva of your design and I will inform you of the results if am done.
Swagatam says
Sure, no problem.
Anthony says
Hello big man, Honestly I am not doing anything different from what you continue to instruct me. I am using the Ainsworth Lynch sg3525 diagram, so, where in the circuit of the ne 555 timer, pin#3 is used to feed the sg3525 two transistors 547, they connect the two oscillation lines of the sg3525 circuit in the inverter diagram, Yes exactly I did, the pin#5 of sg3525 of my construction replaces the feeding pin #3 of the Ne555 timer in your drawing. Am surprised.
Swagatam says
Hello Anthony,
I think you are getting confused
The Ainsworth Lynch circuit will not provide pure sine wave output.
Pin#5 of SG3525 has no role in Ainsworth Lynch circuit.
Pin#5 of SG3525 is an option which can be used for getting slow triangle waves for the op amp cirucit
Anthony says
Hello my instructor, I connect pin#5 of sg3525 to the two transistors for the conversion stage only to see that there is no oscillation at the output of pin#11& pin#14, my meter reading is 0.000and the voltage reading is 0.441volt very bad results. Am really down for my result. Well I am not an electronic product so the difficulty. Thanks for the advice to acquire the handset oscilloscope. I always do well to build the oscillation circuit for every simple inverter that I find. But if you could endure me to complete one of the sg3525 of your simple sine wave inverter I would be grateful. I don’t know where exactly I am lacking in. Thanks big man.
Swagatam says
Pin#5 of SG3525 is an option which can be used for extracting the slow triangle waves and can be used at the op amp pin#3.
Pin#5 generates the slow triangle waves.
Anthony says
Hello Swagatam, Yes I have got 50hz at pin #11 as well as pin #14 really. But unfortunately I don’t have the oscilloscope, only my small multimeter. But thanks for confirming the 90hz, I will connect to see the behavior of the oscillation at pin #11. If my 50hz do not change then I can connect my power transistors. But if you have something very important to advise me about you are very welcome, am very excited myself even though I have not finished. I I even followed you up to YouTube, Thanks again.
Swagatam says
Hello Anthony,
You can use the 90 Hz as the slow triangle waves, it will not affect the sg3525 output frequency.
If you don’t use an oscilloscope then you will not be able to confirm the waveform and the results. How will you check the SPWM generation?
You can easily purchase a small hand held oscilloscope such as the DSO138 which is very cheap and accurate.
Thank you for subscribing to my You tube channel,
Anthony says
Hello Swagatam, I built the oscillator circuit of the sg3525 your design. But at pin#5 as you indicated, the frequency there is more than 50hz, it’s around 90hz plus. And pin#4 is 100hz. You said we need 50hz for slow spwm which we must feed the two 547 transistors. Now what next should I do for the result that I’ve got for my inverter that I am building, please help me out.
Swagatam says
Hello Anthony,
What frequency are you getting at the output pin#11 and pin#14 of the IC? If it is around 50 Hz, then 90 Hz from pin#5 is fine you can use that for the slow triangle waves.
But remember you will need an oscilloscope for checking all the relevant waveforms otherwise it will be impossible for you to confirm the results.
Anthony says
Hello Swag, Please from the standard ic 555 design of the spwm, the fed arrow pins 6&2 of the fast triangle wave is one likewise the pwm design. But the slow triangle wave design has two arrows from 2 pins respectively. Slow triangle wave from pin 6, now where do the one from pin 2 goes to in the construction? By your indication it goes to pin 4 of the sg3525 with the arrow pointing. Supposing I am using this design do I necessarily connect the two pins 6 and 2 of the ic by the arrows directions. I am asking this in the case of the slow triangle wave of the spwm of the ic 555, should one want to use this design. Consider me for my bothering contents, thanks engineer.
Swagatam says
Hello Anthony,
Yes that’s correct, you must do exactly as indicated in the slow triangle wave diagram. This is to ensure that SPWM cycles are exactly in sequence with the 50 Hz frequency cycles of the SG3525. However you can eliminate this 555 stage entirely and get the synchronized slow triangle waves directly from pin#5 of SG3525 which we have already discussed in the previous comments.
Anthony says
Hello Swagatam, I have been trying to realize this sg3525 simple sine wave inverter but was having a problem with the conversion by using the ic 555 circuit before I left. Now reading through over and over I’m having a bit understanding now. Please by your explanation if you use the SPWM circuits, fast and low, the low must have the same frequency 50hz with the main ic sg3525 right. Now if I use your configuration exact will I be able to get a the 50hz or I have to change the capacitor. I asked because I don’t know how to calculate it. And again what’s the Ct you talked about on ic 555 circuit? I am mechanic but love inverters circuit diagram that are not complicated.
Swagatam says
Hello Anthony, yes the slow triangle wave must be 50 Hz or at the frequency that is required at the output of the transformer.
However, this slow frequency must be synchronized with the SG3535 frequency so that the op amp is able to create the exact set of SPWM matching the period of the mosfet ON time.
Therefore in order to synchronize the SPWM with the mosfet switching we can extract the 50 Hz slow triangle from the “Ct” pin of the SG3525. The pin#5 of the IC SG3525 is the Ct pin
Anthony says
Thanks for prompt response, God bless you
Anthony says
Thanks for your prompt response, God bless you. Then it means after I have realized the sg3525 main circuit with my 50hz at the two pins 11&14 of the sg3525. Now I can connect from the pin no. 5 of the main ic sg3525 to the two 547 transistors for conversion for my sine wave for my inverter, is that what you mean?
Swagatam says
No that is not correct. The 50 Hz from pin#5 must be connected to the to the op amp (+) input where the slow triangle waves is suppose to be applied.
Seun says
Good day Sir, Swag, please what can I do to my sg3524 inverter system, when I power freezer at 220v, it works fine but inverter hums.
Swagatam says
Hi Seun,
the humming could be due to overloading of the inverter, you can try using a bigger transformer and see if that solves the problem. To confirm this check the transformer temperature while the freezer is working…if the transformer is getting hotter then surely the problem is due to overload.
Seun says
OK Sir, thanks. Could bjt buffer stage help?
Swagatam says
BJT buffer might not be related to the problem. Th issue could be either due to overloading or due to crude waveform from the inverter.
Seun says
I noticed at 180v quiet even on loads, but at 215v above it gives a loud sound, anything to do, Sir
Swagatam says
Higher voltage will mean more current drawn by the load which can create overloading on the transformer causing vibrations in the transformer and noise. Check the output voltage without the load connected, it could be a lot higher than 215V. You can try adding a capacitor across the transformer output wires and see if that helps.
Seun says
I noticed that at 175v it is quiet and was able power the freezer and gets colder fast than 215v, please why this better efficiency at this voltage.
However, when powered with TV there are moving lines on it.
Please what can be done.
Thanks.
Swagatam says
Not exactly sure, maybe the fridge coils get hotter at 215 V causing inefficient cooling.
The moving lines are due to harmonics in the inverter output waveform. Try adding a capacitor across the inverter output and see if that helps.
Seun says
I have an inverter 1.5kva/24v factory design, used with 150ah battery, the charging setting. Says c6-c3, which one is safe
Swagatam says
I am not sure what c6, c3 means.
Melvis says
So sir when the dead time resistor is correctly fixed he do I know
Swagatam says
It is not critical….By default there will some deadtime even if you don’t connect the external resistor. If you add a resistor that will increase the deadtime….Check the output average DC across the output, it should not be less than 40% of the battery voltage, this will prove an optimal deadtime value….or you can also check it with a oscilloscope. Remember higher deadtime will decrease the output inverter voltage proportionately.
Melvis says
One more thing sir,how is the dead time resistor calculated and also what’s the function of p4 in the first design
Swagatam says
I don’t have the formula for the dead time resistor. You will have to fix it by trial an d error by measuring the average DC across the output pins. With minimum dead time the voltage across the output pins will be almost equal to 50% of the battery DC…this will becomes lesser and lesser as the dead time is increased. P4 ensures that when the battery voltage reaches its low battery level the opamp output becomes high and latches. This latch breaks and the opamp output turns low again only when the battery is charged to a reasonably good position.
You can remove P4 and the series R9 resistor if you want, they are not too important.
Melvis says
Hello sir, which of the ic741 needs the fast triangle wave ,pin 3or2
Swagatam says
Hi Melvis, the fast triangle wave should be on pin#2
Prachi says
I need to know dead time for full bridge or 3525 IC dead time used for full bridge . Also how to do Transformer design Full Bridge ?? any application note ???
prachi says
can any one help me ??? 1200w full bridge transformer design using 3525
Swagatam says
A resistor connected across pin#7 and pin#5 determines the dead time of the IC.
Do you want to connect a transformer to a full bridge circuit?
Anupam Dasgupta says
Hi,
Thanks for publishing such a nice project. I have a mind to construct the same if I can procure all the components online because the place where I live in is a remote one and it is hard to find all the components locally. Regarding automatic correction feature I have a question, once the voltage at pin2 is set through preset P2 is there any chance of increase/decrease this voltage as explained ? Rather the voltage at pin1 will increase/decrease as per output voltage. As you have explained Would you please explain it a bit more.
Swagatam says
Hi, thanks and glad you liked the project! Once the automatic correction is set, the output voltage will remain constant and will not rise above the set threshold. However, if the load increases beyond the capacity of the inverter then the voltage might drop below the set threshold since the inverter will be unable to supply extra power to the load due to lack of transformer and battery power. So voltage will not rise beyond the set threshold this is guaranteed, but the voltage will not drop is not guaranteed.
anil says
Hi, my name is anil . I need a high frequency inverter for a research i am conducting. Can you plz send me the schema of your circuit. Otherwise, is there another way to have your circuit schema or your prototype ?
Swagatam says
Hi Anil, you can try the last circuit shown in the following article:
https://www.homemade-circuits.com/half-bridge-mosfet-driver-ic-irs21531d/
Seun says
Hello Sir, please how can I incorporate self charging system to my inverter without draining,
Swagatam says
Seun, you can use one of the circuits from the following article to get an automatic charging cut offs:
https://www.homemade-circuits.com/opamp-low-high-battery-charger/
Ricardo says
Hello Mr. Swagatam,
First of all thank you very much for your work.
I have some questions, I’m looking for a simple sine wave schematic for 25v – 230v 50Hz 1500w with feedback.
I don’t know if it will be valid to change Design#3
Can you help me please?
Thank you so much.
Swagatam says
Hello Ricardo, you can use Design#3 to create a sine wave inverter, however, the mosfet gates will need to be chopped using SPWM for achieving the intended sine wave output.
Ricardo says
Hello Mr. Swagatam,
Thanks for you replay.
Sorry i have some more questions, can i use P75NF75 mosfets?
How many will be needed for a power of 1500W?
Thank’s for your time.
Swagatam says
Hello Ricardo, you can use 2 mosfets in parallel on each channel if the battery is 24V.
Bode says
Good day sir thanks for replying to my earlier comments.please the question I want to ask is about ups
I noticed that my ups power output is about 600w instead of around 800w. Is there a way to increase the power factor
Thank you very much
Swagatam says
Hello Bode, to increase the wattage capacity of an inverter you will have upgrade its transformer, battery and the mosfets appropriately. To improve power factor you may have to use a full bridge inverter instead of a center tap inverter
Calculate Battery, Transformer, MOSFET in Inverter
Bode says
Good day sir,
Concerning the mosfet bank , can I use a low amp mosfet like 10a i.e using ten 10a instead of two 50a mosfet.will it protect the mosfet bank and make less noise
Thank you very much sir.
Swagatam says
Hello Bode, yes you can do that.
Anthony says
Thanks sir for your comment, it really helped.
I just want to clarify myself to avoid mistakes.
There are many ground wires in the circuit, the one going to the minus side of the battery is it the ground wire with a switch by the left side of the circuit.
Also sir is the wave output pure sine or modified sine.
If we want to increase the wattage output, what can we do, if we are to add more mosfets, how are we to add them to suit the circuit. Then lastly pls can we in place of the 9-0-9 trans. use 12-0-12 trans. with a higher amp.
Thanks for answering.
Thanks for answering
Swagatam says
You are welcome Anthony, I guess you are referring to the 3rd schematic. Yes all those connections having the ground symbols will need to be connected in common, and this common line will need to be connected with the battery negative. After joining all the grounds in common, you can connect the battery negative to the MOSFET source terminals.
The waveform is square wave.
For increasing output you can connect mosfets in parallel, increase battery Ah value,, and increase the transformer current rating proportionately. You can connect the relevant GDS terminals of all the MOSFETs in parallel.
If you use 12V trafo with a 12V battery then if your battery drops to 11V, your trafo output will drop to 200 V and so on.
Anthony says
Hello sir, how are you doing, pls I want to ask under Design#1, you posted under it another circuit with automatic feedback correction, pls I want to ask I cannot identify the minus side of battery in the circuit, also the pin 3 and 4 are not connected to anything, then the mosfets IRF540 aren’t calibrated GDS to help us know where to connect the wires going to them, then pls lastly on the transformer side you wrote BR1, what does it mean pls
Swagatam says
Hello Anthony,
The supply line with ground symbol is the negative of the circuit. The pin3 and 4 are not relevant to the circuit so they are unconnected. You can easily understand the mosfet GDS simply by looking at the mosfet diagram. If you cannot identify the mosfet piouts then how will you build the complete inverter circuit? BR1 is the bridge rectifier.
B.K.LEELESH says
sir,
I have successfully constructed the inverter design 2. and it is working satisfactorily. Still i have follwing doubts.
In one of your earlier post pin 1 of ic.sg3525 is connected to pin 9. and P3 is connected to pin 2. But in the above design no.2, pin 1 is connected to P3 through D5 and pin 9 is left idle. In my construction I have followed the earlier design connecting pin 1 and 9. and P3 to pin 2 through D5. Is it ok sir.
Further I want to add a snubber circuit to the mosfet. Is it necessary sir.
Thanking you,
LEELESH.
Swagatam says
Thank you Leelesh, for updating your results.
There may be slight differences within these circuits, but all are correct. Pin1 and pin9 can be connected through a resistor as shown in a few of the designs. However the preset connections must be as given in the first and the second schematics since it was designed with proper research.
You can check out the following article to understand the pinouts details comprehensively.
https://www.homemade-circuits.com/understanding-sg3525-ic-pin-outs/?showComment=1357274945738
You can add external diodes across drain and source of the mosfet and also across the gate resistor….for details you may refer to the following article:
How to Protect MOSFETs – Basics Explained
Romeo Olida says
My project will be pure sine wave inverter with the SG3525 chip. So, if the inverter frequency will be 60Hz, the SG3525 should have an oscillator frequency of around 60 x 2, or 120kHz ? Is it right ? Thank You Sir.
Swagatam says
That is correct.
sameer alsaleh says
thank you very much
Godspower says
Good day Mr Swag, pls something is not clear to me regarding the above universal circuit that can be used to convert any square wave form to pure sine sine wave. You said in your statement and I quote (Preferably, the PWM input frequency should be 4 times more than the base 50 or 60Hz frequency. so that each 50/60Hz cycles are broken into 4 or 5 pieces and not more than this, which could otherwise give rise to unwanted harmonics and mosfet heating).
Sir if I get you ryt,
1. Do you mean that the oscillator frequency that is already set to 50hz from pin 11 &14 should be increased to 200hrz? Am not clear sir, please kindly shield more light for me to understand sir. Thanks you sir.
Swagatam says
Hello Godspower,
The 50 Hz frequency coming out from pin11/14 is chopped by the PWM frequency. This PWM frequency which is acquired from the 555 circuit must be 4 or 5 times more than the 50 Hz frequency.
Godspower says
Thank you very much sir, now i understand.
Swagatam says
You are welcome Godspower!
Seun says
Good day Swag, please when I connect an electric pressing iron with freezer on my built 5kva inverter, my light bulbs begin to be unstable, please what can I do.
Swagatam says
Hi Seun, you can add more batteries in parallel only for the initial switch ON periods and then remove them…however if the 5kva rating is not sufficient for the initial high power consumption by the heater then the batteries might not help
Seun says
Thanks Sir, please how can I prevent the sg3525 from effects of lightning, it destroyed the Ic
Swagatam says
Hi Seun, it can be difficult to save any electronic equipment from lightening strike, however you can try connecting the inverter body and transformer with a good earthing line, and hope it works.
Seun says
Good day Sir, between 120v and 144v DC input, which do you recommend with better design for higher efficiency and worthwhile. Thanks
Swagatam says
Hi Seun, which circuit are you referring to?
Seun says
Adapting the sg3525 circuit for inverter, with 10-12 batteries in series, will you recommend with better design for higher efficiency and worthwhile. Thanks
Swagatam says
You will need a transformer that can transform the battery voltage 220V. If you want to have a 120V AC output with transformer then you will need full bridge inverter with a 120V DC input
Onyeka says
Good day Swagatam, I usually have problem selecting the right mosfet(and the right number too) for inverter, could you please help me with a small explanation, say I want to design 1000va inverter push pull topology with 12vdc input, what should I look out for in a MOSFET, and how many am I supposed to use.
Swagatam says
Hello Onyeka, you can read the following article for all the required information:
https://www.homemade-circuits.com/how-to-calculate-and-match-inverter/
Mitech says
Good day sir, Thanks for the circuits and lectures on Electronics you give out for free. I must confess I’ve learnt a lot through your website because it gives me details of everything I want. Thanks for that. I have few questions to ask concerning this inverter Design:
1) With the Pot at the 555 timer circuit which is used to set the RMS of the output voltage, will the output voltage of the inverter change when loading the Inverter?
2) If yes for Question 1, how can I add autovoltage correction feature to the inverter?
3) Will the inverter have the same peak value of voltage with Pure sine wave?
4) How can I reduce the no load Current and excess noise from SG3525 Inverter?
Waiting for your candid really.
Swagatam says
You are welcome Mitech,
1) No, the output voltage will not be stabilized using the IC 555 RMS control.
2) Figures 1, 2, 3 all have auto voltage correction feature.
3) Yes the output peak value will be standard 310V depending on the transformer specs.
4) You can try using highly stabilized and regulated DC supply for the SG3525, possibly through an inductor.
Godspower says
Good sir Mr swagatam, thanks so much for the previous response.
My question is, from the no 3 circuit diagram, can the following changes be made or replaced in the circuit
Presset 22k to 10k or 100k or 50k
Presset 47k to 10k or 100k or 50k 20k respectively bcos I couldn’t find 22k and 47k presset. Am sorry if my question is too much am still a hobyist trying to know more sir. Thank you sir
Swagatam says
Hello Godspower, I cannot see any presets in the 3rd diagram??
Godspower says
SIR I MEAN THE CIRCUIT YOU REPLIED TO MR (Anas).
Swagatam says
You mean the 3rd diagram from bottom? You can replace the IC 555 100k preset with 50k preset, but I cannot suggest about the SG3525 prests, since they are related to the PWM and frequency, so changing the presets can alter its output performance.
Godspower says
It is clear sir, thanks very much sir.
Swagatam says
No problem, Godspower!
Nimel says
Good morning Mr Swag, for the 2nd design do i take the slow triangle frequency (50hz) from pin4 of the sg3525 or from pin 5
Swagatam says
Hello Nimel, the slow triangle can be taken from across C1, you will need an oscilloscope for testing this
Nimel says
But sir,why not the pin4
Swagatam says
pin#4 will not provide triangle wave, it will give square wave.
Godspower says
Good day sir, am currently working on the first circuit. I have T2
12-0-12 500mA will it work?
T1 6.8-0- 6.8 centertaped ups transformer for the inverter itself, will it be ok?
Swagatam says
Hello Godspower, yes those transformers look OK to me, however you can totally avoid T2 if you use the 3rd circuit.
Godspower says
Thank you so much sir for been here for me alway, as an electronics hobbyist I believe I can do it.
Swagatam says
You are welcome Godspower!
Godspower says
Good day sir Mr Swag am greatful for all the quick response. Please sir from the low battery cut off LM 741 in the first circuit, pin7 is positive while pin4 is negative, please should I connect this pin to positive and negative of my battery respectively? Or should I leave it the way it is? Or should I link it to the positive and negative input of I.C 1 ? .
Swagatam says
Thank you Godspower, yes you must connect the supply pins of IC 741 with the battery terminals, or you can also connect them in parallel with the SG3525 supply pins
Godspower says
Please sir as I was looking for this capacitor today to buy (C1 = 0.1uF/50V MKT), it was not available. Pls sir kindly suggest another CAPACITOR for me since I could not find the one stated above.
Swagatam says
Godspower, you can use 0.1uF ceramic capacitor also.
Godspower says
Thank you very much Mr Swag for your support towards everyone in this site. I pray abundant blessings in your home. Thanks.
Swagatam says
You are welcome Godspower!!
Nimel says
Plz sir, I’m the 3kva inverter design i’m thinking of replacing the 20nos irf540 with 6nos of irf3205 would that be ok sir
Swagatam says
Hi Nimel, yes you can do that!
Godspower says
Please what type of other capacitor can I use to replace the following capacitor.C2, C3, C4, C5 = 100nF or can I use 104 those green type?
Swagatam says
you can use any type of 0.1uF (104) capacitor
Godspower says
Ok thank you so much sir am greatful sir.
Eniola says
Also the discharge pin (R8) is it 100ohm or 100kiloohm or 100k? Please looking forward to your quick response
Swagatam says
Please specify the diagram that you are referring to?
Eniola says
I mean the sg3525 in in the pwm feed side( chopper signal side). the discharge pin is only 100,is it 100 ohm or 100k?
Swagatam says
Please show me the exact diagram, I cannot see 100 written anywhere.
Eniola says
Also how should l connect the preset to as to modulate the pwm? Thanks I will be looking forward to your quick response
Swagatam says
PWM modulation is done using P3, to adjust the RMS output voltage
eniola says
i mean your last circuit with an inductor of 100UH,220/25v capacitor and 15v zenal diode.the pin 16 has an 12kconnected to pin 2, my question is can i add 22k at the pin 16 so as to control the PWM?since pin 16 is the refrence voltage.
Swagatam says
you will need a potential at pin2, just changing the 12k will not help….please refer to the other diagrams, and see how pin2 is configured with a resistive divider
Eniola says
Sir can I connect a 22k preset across the pin 2,so as to vary the pwm from pin 11 and 14?
Swagatam says
Yes you can use it!
Nimel says
plz sir, what is the difference between SPWM and PWM that make them use PNP and NPN BJTs respectitely
Swagatam says
In PWM the pulse blocks are all equal, in SPWM the pulse block width change proportionately simulating a sine waveform. SPWM is a digital equivalent of analogue sine wave, you can learn more in the following article:
https://www.homemade-circuits.com/how-to-generate-sinewave-pwm/
Nimel says
Nice article mr swag
Swagatam says
Thank you!
Obinna says
Please I want to make inverter of 3.5kva please how can the diagram be
Swagatam says
first build the basic low power inverter, then increase the transformer, mosfet, and battery specs proportionately to achieve the desired high power output.
Johnny says
Hello thanks for ur reply
im using 10Ohm for the gate of the Mosfet
is it ok to test with the IRFZ46 ?
i will try the Bc547/557
the connection is simple
2 bases together through 10k to oscillator of sg3524
2 emmiters together to Mosfet gate through 10Ohm resistor
the Collector of Npn Transistor to 12v+
the Collector of Pnp Transistor to 12v-
thanks for your help
Swagatam says
You can use any mosfet for testing, provided the output load is compatible with the mosfet specs.
yes the mentioned connections are OK.
You can connect a 1N4148 diode parallel to the 10k base resistors, just to ensure that the BC547 is switched OFF correctly during the OFF cycles from the IC. Anode will towards the base as shown in the following diagram
The 10k between gate/source is optional in this condition.
Johnny says
Hello Sir
i have tested two push pull transistors to drive the Mosfets bd139/140
one mistake i had is there was 10k resistor connected on Mosfet Gate & Source Which was working when driving the Mosfet directly from Sg3524 directly through 10Ohm resistor
the Mosfets got fired
is it the 10k the problem ? or the bd139/140?
i still have 2 spare irfz46 to test & im afraid to fire theb i have to wait to get new ones for testing
your help is very appreciated
Swagatam says
Hello Johnny, both the things are technically OK, and cannot be the cause of the problem.
However, I would recommend using BC547/BC557 instead of BD139/BD140 for the gate switching of the mosfets, and also make sure to use the 10 ohm in series with the gates of each mosfet.
Prince says
hello, pls am working on 10 kva inverter at 48v pls what mosfet are best for 48v by 10kva and i new a diagram on the oscillator unit to a mosfet stage ,sine wave.
Swagatam says
You can use IRF3205 5nos in parallel, on each channel.
frantisek says
Hi, i want to use the sg3525a for a class D amplifier to modulate the audio signal. I am not sure which pin to actually feed the audio signal into. thanks for any advice.
Swagatam says
Hi, I don’t think SG3525 will accept an analogue signal for the modulation, it can only accept logical high and low input signals.
Daoud says
Bonsoir monsieur. J’ai un soucis.
Bon, pour mes petites expériences si je n’utilise pas la broche( no 2) de régulation pour la sortie. est-ce que mon montage va fonctionner ou pas ? J’aurai la tension à la sortie de transformateur ?
Swagatam says
Good day Daoud, no problem if you do not use the pin2 error amp, your inverter will still work normally, although the output voltage will not be controlled and it maybe relatively higher initially while the battery is fully charged
Paul England says
Swagatam,
Thank you for the suggestions and I will certainly try them. I have already put a 0.68uF capacitor across the output of the transformer and it has ‘quenched’ the spikes somewhat.
I would add that I have not had this problem with other square wave sources which I have used only the SG3525.
If all else fails I will add Schmitt triggers to the output which should solve the problem.
I will let you know my findings.
Swagatam says
Thanks Paul, that makes sense, I hope it solves the problem!
Paul England says
Swagatam,
Whenever I use the SG3525 I seem to get a noisy ‘spiky’ output and not a clean waveform.
Do you know the reason for this?
Swagatam says
Hi Paul, it may not be because of the IC, rather because of the spikes from the transformer. You must provide the supply to the IC through a 100 ohm resistor, and add a filter capacitor and zener diode right across the supply pins of the IC….these measures might help to get rid of the noisy waveform. You can also try adding low value high voltage capacitors across the output wires of the transformer
Ramesh says
Hi Swag,
Can i generate variable frequency using this 3525 IC?
Run time dynamically i want to change it.
Thanks
Swagatam says
Hi Ramesh,
yes definitely you can use this IC to generate a variable frequency, by using an adjustable resistor for Rt at pin#6
Ramesh says
How i can change run time that resister. I am thinking human independent system and frequency must be changed from 50khz to 200khz within a second. I can give voltage reference for that as a feedback.
Swagatam says
If you want the change to happen in two steps, that is, jump from initial 50kHz to 200kHz, then that can be easily achieved, but if you want it to happen gradually then that can be difficult, and we may have to employ an LED/LDR optocoupler for this.
M.H.Z says
Hello
Excuse me I want to make a circuit for convert 12v to 36v dual with 600W power for car amp.
I ask you , introduce me a circuit map for this
thanks a lot
Swagatam says
Hi, you can try the following circuit
https://www.homemade-circuits.com/high-power-dc-to-dc-converter-circuit-12-v-to-30-v-variable/
you will have to make two such circuits for getting a dual output
Seun says
Please Swag, for modified inverter using this sg3524 circuit without conversion to pure sine, will sziklair pair work better than ordinary transistor at the output pin 11 and pin 14.
Thanks
Swagatam says
Hi Seun, yes it will work better than a single transistor, quite like a Darlington pair.
Seun says
Hello Sir, please Which complete solar-battery-inverter system will you recommend to power led Tv 43”, fridge, 1hp pumping machine, 1hp inverter Ac and other small loads.
Thanks Swag.
Swagatam says
Hello Seun, you can use the second circuit from the following article and configure it with a 15V 25 amp solar panel for getting the required results.
You can also try the following design with a solar panel for the same results:
1500 watt PWM Sinewave Inverter Circuit
Seun says
My 2.5kva inverter, while on load is quieter than without load, what could be the reason. Thanks Sir.
Swagatam says
It is probably because, due to increased load, the harmonics get damped and the waveform becomes cleaner.
Magesty construction & property developer Nig ltd says
BATTERY
Battery rated voltage (DC) 12V system
Rated power (W) 500W or higher
INVERTER
input voltage range (V AC)
input frequency (Hz) 50Hz
output voltage (Hz) 220V AC
output frequency (Hz) 50 HZ
specification of inbuilt battery : Lithium ion(not lead acid battery)
SOLAR INPUT
solar panel wattage: 100w or higher
input charge controller type: MPPT
rated PV charge current: 30A or higher
Solar panel mounting kit: Must be included
DC OUTPUT
5V DC USB output Yes
12 V DC output Yes
we shall be waiting for your swift response for the best price and product
Thanks
Swagatam says
Sorry, we don’t sell readymade units or kits from this website.
Jan says
Hi Swagatam,
Can I use a transformer – Prim 0V-9V. (No center tap) Sec 220V instead of 8-0-8V transformer for TR1? I would also like to use BJT’s instead of Mosfet’s. If so can you please suggest a circuit to do this from PIN 11 & 14 of the SG3525?
Your assistance will be much appreciated.
Regards
Jan
Swagatam says
Hi Jan, if you use a transformer without a center trap with SG3525 or any other oscillator IC, the output will not be an AC, rather will be a pulsating DC. To get an AC output you will need an H bridge circuit.
You can try the following configuration for getting a single ended output from the SG3525. The transformer can be connected across the collector and ground of the circuit, the transistor and the resistor values will depend on the transformer current rating. Make sure to connect a protection diode across the transistor emitter/collector to safeguard it from the transformer reverse EMFs
https://www.homemade-circuits.com/wp-content/uploads/2021/05/SG3525-single-ended-operation-compressed.jpg
Paul England says
Swagatam,
Regarding the use of the SG3525 I have built an inverter which has a 32V output on the secondary side of the transformer and have used a bridge rectifier fed from it to provide feedback control. However, I have not been able to find any data on what voltage range to use to control the duty cycle of the SG3525. I am using a pot. at the moment and am getting a voltage range of 0.8V to 28V. Will this be sufficient to set up the initial operation? Obviously I don’t want to damage the chip in any way.
Swagatam says
Hello Paul, the tripping point will depend on how much reference level is selected for the pin2 of the error amp. pin1 is the non-inverting input of the error amp, pin2 is the inverting iput of the error opamp. The pin1 is fed with the feedback from the output, once this feedback crosses the pin2 reference level, the IC will execute the PWM narrowing of the output.
Normally the reference at pin2 is derived through the 5V supply available at pin16 of the IC. This 5V can be subsequently reduced to some desired lower level either through a resistive divider or a preset.
Inverter Circuit with Feedback Control
Paul England says
Swagatam,
Thank you now I understand.
Swagatam says
You are welcome Paul!
Jan says
Hi Swagatam,
I have built the Design No. 1 – 2nd diagram of the “3 High Power SG3525 Pure Sinewave Inverter Circuits”. Problem is that I get no output signal on Pin 11 & 14. I don’t have a load on these two outputs at present. Does that matter?
I use a 12V battery as power supply and TR2 as feedback.
I have adjusted P5 so that I can get a low on IC1-10
Also P3 adjusted to give +2V Full wave 50Hz signal.
IC1-5 gives a saw tooth signal of +2.5V @8.6Khz
Pin 4 also gives a signal but is not connected.
I have replaced IC1, but still the same problem.
Please can you assist?
Regards
Jan
Swagatam says
Hi Jan, is the IC oscillating? Please check the OSC out pin and check with a frequency meter whether this pin is producing the frequency or not.
You can also measure the same across the Ct capacitor.
For more details of the pinout you can refer to the following article:
Understanding SG3525 IC Pinouts
Mitech says
Remove the 741 Op amp IC and test the circuit again, you will get output this time provided that you built the circuit correctly. 741 low output is not 0 volt rather it’s about 1.3v or more and it’s enough to shutdown the SG3525 IC.
Swagatam says
In the second diagram, the zener diode D7 is provided exactly for that, to prevent the IC 741 offset voltage
Priyam Sharma says
Sir! How to add the charging capabilities to this inverter circuit.
Please describe 😊
Swagatam says
You can add a an external battery charger with the inverter. When you connect the charger to the AC mains, it will start charging the battery.
Rk says
Sir Please make a circuit digram on single phase shine wave inverter siganal convert to three phase signal generator for three phase shine wave inverter
Seun says
Sir I have 2 inverter systems, first 1kva/24v, the other 3kva/48v both 400ah battery bank, but when I load at night with my freezer, why is it that the 3kva/48v runs down faster.
Swagatam says
Suen, I can’t be sure why that happens without checking it physically, can be difficult to judge the fault…seems to be a specific fault with the 3kva inverter…
Seun says
Thanks Sir, can’t be higher no load current than the 24v system
Swagatam says
Sorry I did not correctly understand your question…
Mahasetra says
Hi, thank you for such a great article.
I want to make a simple sg3525 inverter (modified square wave) with a low battery voltage disconnect.
I want it to disconnect at 11.8V and reconnect at 12.6V and I want to know how to implement this. (The exact calculation of P4 and R9 according to the 2nd circuit to implement this Vth_low= 11.8V and Vth_high= 12.6V) or do I have to test it in real and vary the pot?
Also, what is the more efficient way to implement this low voltage protection: using an op amp as comparator as in your circuit or using a ne555 as a bistable latch (1/3 * vcc ; 2/3 * vcc etc) ?
Thank you
Swagatam says
Hi, all the information is already given in the article…for the exact frequency calculations you will have to build it and the find the results by testing with oscilloscope and meter.
pefeck clovis says
Please can two different power mosfet be used in an inverter circuit?
Swagatam says
yes it is possible, if the power rating of the MOSFETs are in accordance with the load
Felix Elizeche says
Ing..pregunto
1- Sí se podría cambiar BC547/557 por BF 422/423
2- Al estar en funcionamiento el inversor ,,Qué determina el consumo del circuito sin carga osea sin uso, cuanto deberia de consumir….podría medir con un amperímetro desde la batería…?..y se supone que al tener una carga aumentara el consumo…
Ifeanyichukwu says
Mr swag pls I’m having a little problem understanding how to get 400hz from the values 18k50k present and 10k resistors along with a 1nf capacitor isn’t that value to small to get 400hz pls help me or is the sample above perfect for use
Swagatam says
Mr.Ifeanyichukwu please don’t depend on formulas or the diagram, instead buy one oscilloscope or a frequency meter and check the results practically for setting up the frequency
Christopher Omoigui says
Thank you Mr Swaggatam. I have been following your post and really want to thank you because they have been amazing.
The circuits above are really wonderful but could you please give us a design for 24V, 36V, and 48V 3KVA and 5KVA pure sine wave inverter.
And is there any anduino design for simulating the pure sine wave for use as the oscillator circuit in a 3kva or 5kva inverter?
Swagatam says
Thank you Christopher, you can find a 48 V inverter in the following post:
1500 watt PWM Sinewave Inverter Circuit
You can use the following Arduino code for implementing as sinewave oscillator:
Arduino Pure Sine Wave Inverter Circuit with Full Program Code
Seun says
Good day Sir, please what could be responsible for damage of fan used for cooling inverter
Swagatam says
Hi Seun, the damage could be due to fan’s internal issues, not related to the inverter. Still you can try adding a voltage regulator through LM338 etc for the new fan to ensure better safety….
Seun says
Please between 48v system using 4*40ah batteries and 12v system using 1*160ah battery which one is more efficient and why, Sir
Swagatam says
4 x 40 Ah is efficient since higher voltage will mean lower current and thinner wires and smaller transformer
Tom Kenefick says
I am looking for your circuit that puts out 110ac and 220ac. I think it put out 5000 watts.
I want to build a solid state generator that gets the energy from the earth or the sky.
I want to hook it up to my main breaker box to run the house and maybe make the electric meter run backwards.
I saved your circuit, but now I can’t find it.
Oluwaseyi says
I’ve searched everywhere for the proteus library file for the SG3525 IC but can’t find it. I need to design and simulate my SG3525 inverter on proteus.
Help!!!
Swagatam says
Sorry, I do not use softwares, so no ideas!
Seun says
Please Sir, please how can I add a cold start to the inverter circuit
Swagatam says
Seun, please explain the requirement elaborately
Seun says
When I put on the inverter, there is instant surge, but a cold start will allow the inverter to come on without the surge
Swagatam says
To implement this, the inverter must be switched ON without any load, once the inverter is switched ON, then the load can be switched ON, this will prevent the the inverter devices from a possible surge
Godfrey says
Please sir, can you help me with the circuit diagram for 200W pure sine wave inverter?
Swagatam says
Godfrey, the sine wave concept is already explained in the above article, you can easily customize them to your required specs
Godfrey says
Please I want to find out information on the settings of the presets
Dimitris says
Hi!! i made the circuit using pwm signal (ne555) but i am facing a problem.. When i connect a bulb (regular or led) the inverter works fine and leds doesnt flick at all.. But when i connect an appliance (laptop charger or a pc monitor) then immediately Mosfets blow up! could you please help me?
thanks!
Swagatam says
Hi, what was the wattage of the bulb you used? Please try using a 60 watt bulb, and check the issue. I think your inverter lacks power. Also, make sure to use reverse diodes across drain/source of the MOSFETs and see if that solves the issue.
Try adding all the measures explained in the following post
How to Protect MOSFETs – Basics Explained
Dimitris says
Thanks for your prompt reply! The bulb i used was 60watt and was working fine.. Not even got hot the mosfets.. I ll try the reversed diodes you mentioned.
Swagatam says
OK thanks!
Dimitris says
i put the reversed diodes as you told me. I checked first using a 60w bulb and everything was ok.. then i connected a 220/12v power supply to light a 12v bulb and now the explosion came from sg3525 and not from mosfets, so i dont think my inverter lucks power. Any other idea sir?
Thanks a lot
Swagatam says
Please provide the details regarding the exact schematic which you built and what protection you used for the IC and the MOSFETs, and did you use a PCB or a breadboard?
Dimitris says
i built the circuit you post its pcb but i built it in breadboard.. i add also the reversed diodes for mosfet protections.. now the mosfets arent blow up, but as i told you the ic exploded.. too strange.. could you please provide me gerber files of pcb if it is possible to constructed again in pcb?
thanks
Swagatam says
For prototyping PCB is not required, but it should be assembled by soldering on a stripboard so that the connections are sound. The IC will need protection too, as indicated in the diagrams. The 12V to the IC must eb fed through a inductor or a 100 ohm resistor, followed by a couple capacitors and a zener diode. Please include the parts C16, C17, D3 and the inductor which will ensure that the IC is safe from any sort of dangerous transients:
https://www.homemade-circuits.com/wp-content/uploads/2016/08/sg3525-2.png
You cab replace the inductor with a 100 ohm resistor
I do not have the gerber files for any of the designs
B G Prasad says
Dear Sir,
I have lost job in lock down and trying to set up my own.
may i get some opportunity for pcb design also i can supply transformer any where in India( not ferrite core at this point of time).
Also i can supply Eletronics kit.
Regards,
B G Prasad.
Seun says
Please sir, what cable gauge should I use for 5kva/48v inverter to be connected to the batteries, for positive and negative line.
Also, I used to use swg guage 13 for my 1kva inverter to run the parallel of drain and source of MOSFETs, please what Should I use for 5kva. Thanks sir Swag
Swagatam says
Seun, 8 SWG looks OK to me for 5kva.
MD Ken bion says
Hi Mr swagatam ,,I find this posts very educative and correct,sir I built the 3kva and it works fine,thanks to you..
But I have a problem with the simple alternative of 5000w u posted last..,I built it as designed but it just won’t produce an output,,,every other parameters are ok,,is there any error in the drawing sir,,bcus I’ve cross-checked over and over again,,even changed ic ,,it still won’t work
Swagatam says
Thank you Mr MD,
Actually, upgrading an inverter to any desired wattage level is just about adding more MOSFETs in parallel to meet the wattage specs, along with upgrading the transformer and the battery accordingly.
So the last circuit does not specifically signify a 5kv inverter, you can use of the circuits explained above or anywhere on the internet and upgrade it to the required power output levels, by using suitably rated power devices, transformer and the battery
MD Ken bion says
Ok sir thanks I understand now.,though my problem is that led indicates power is entering the circuit,,,but nothing at the output stage from ic to mosfets…..
Pls sir …….
I used your sine wave converter design and it’s so cool,so I tried it with 4047 circuit wich has a 0.22pin1 and 19kpin2,in parallel with pin3,,,,pins 7,8,9,12, to ground,,,and 4,5,6,14, to +12v,,,,,,it works but ic4047 dies when theres any little sparkle when connecting load (bulb)…..how do I stop this sir?
Pls help
Swagatam says
Hi MD, you will have make the entire circuit stagewise. First you must try completing a basic 100 watt design and confirm its working. Once confirmed then go on adding the parallel MOSFETs, and increase the transformer/battery wattage, to increase the output handling capacity upto the desired levels.
For the 4047 IC, you will have to add a few extra parts across its supply terminals to safeguard it from the transformer back EMFs….and also make sure to add freeeheeling diodes across the transformer primary taps, or MOSFeT darin/source terminals. All these details can be found in this article:
https://www.homemade-circuits.com/500-watt-inverter-circuit-with-battery-charger/
Seun says
Good day Swagatam, please does resistive load drawing 7%amps of the battery Ah have effects on the battery and the inverter, how sir.
Swagatam says
Hi Seun, lead batteries can be discharged safely at 10% of their Ah rating, so 7% draw is fine, no matter whether the load is resistive or inductive.
Stephen says
Hello
Must the feedback transformer in the circuit must be 9v 100mah or is there any alternative
Akshaya says
Can I use this circuit with 12v dc 7.2Ah battery.will it work then?
Swagatam says
yes you can
Decipher says
Dear swagatam
Mosfets in my homemade inverter using sg3525 keep overheating till they burn even though attached to a heatsink.
And every thing in my circuit is connected right, what can i do to stop this pls
Swagatam says
Dear Decipher, heatsink will not help if the inverter is accompanied with issues. Try building a basic SG3525 inverter module first, and check if it works normally or not. If still it heats up then the MOSFETs could be faulty. You can also verify by disconnecting the MOSFET gates from the IC and keeping the gates connected to their source pins via 1k resistors….
Ehsan Firouzi says
Dear Sir
Hello . I need a circuit to drive my ultrasonic sewing machin . The output must be 1000w sin wave 20 khz frequency. Can you guide me? I need high frequency AC . The output voltage is less 100 v . Thanks in advance
Swagatam says
Hello Ehsan, what is the input voltage to the inverter, is it from 12 V battery?
Ehsan Firouzi says
Hi .the input voltage is 220 v AC
Swagatam says
OK, in that case you will need to first rectify the 220V AC to 310V DC, then oscillate this 310V DC into the required 220V high frequency AC using the following full bridge driver circuit:
Simplest Full Bridge Inverter Circuit
Adeyemi says
Good day sir, Swagatam, I want to ask if 3 500watts/12v inverters are paralleled at the Ac side to power a 150watts freezer because I have over 1kwatts solar array for my 12v 100ah battery by 10am the battery is full and solar charges are wasting. Not feasible to get more batteries for now. Please advice sir.
Swagatam says
Adeyemi, if you connect the AC sides in parallel and if one of the sides is out of phase may cause instant short circuit burning of the inverter, so this is not recommended.
Adeyemi says
Sir, between 220v and 200v ac output voltage, which one is better to set inverter for good efficiency and why sir
Swagatam says
220V is the standard recommended AC grid value at 50 Hz, and therefore it is 220V which must be set at the inverter output.
Adeyemi says
Good day sir, which appropriate battery ah is good to do the testing of inverter at no load, because using 18ah, 40ah and 100ah batteries gave different readings of current at no load, why is it that
Swagatam says
Adeyemi, that means there’s something no right in your inverter, because at no load all those batteries should have produced the same amount of quiescent current.
Adeyemi says
I just got the reason for the tripping off- sulphation because it was left for 4 months after buying, and used once without recharging and now trips off at 13.2v. I am off grid, so won’t it affect my inverter when I connect your homemade desulphator, trafo type. Thanks sir Swag
Swagatam says
Hi Adeyemi, Batteries generally do not become bad in just 4 months, so you can try charging it in the normal method externally, with 10% Ah current, and see how it works. If possible include a float charge in the circuit. You can use 25% Ah current and then reduce it to 10% after the voltage has reached 13V
Felix Elizeche.M says
Hello Ing. Very grateful for your excellent circuits .. I cannot find information with termination N what I have
1- I would like to know the difference of the CI: SG3525 with SG3524 ,,
2- The SG3524B or N would be the same ..? since ending N is what I get
Swagatam says
Thank you Felix, I don’t think the suffix has anything crucial, as far as the iC operation is concerned, so you can safely use any SG3524 or SG3525 variant for a specified PWM application
Adeyemi says
Hello, please can I tune this circuit to 30hz to us for my ac motor
Swagatam says
Please check the datasheet of the IC, if it allows 30 Hz then you can do it.
Abiola Sunday says
Dear, Master Swagatam,
please, can I implemented the BJT buffer and the PWM circuit in a 3524 inverter circuit that I already built.
would it work, as its not a 3525 IC type used in your designs. What will happens if used.
Can you also hele implement this with a circuit diagram for me to see sir.
Swagatam says
Abiola, the BJT buffer stage can be used with any oscillator circuit, so there’s no issue.
Patrick says
Good day sir,
Sir,i know your ability to extrapolate on practical from theory is undeniable ,i would like to know if Anas circuit above which you amended to sine-wave is a tested and workable circuit?.The circuit draft is to my liking….that i dont wnt to wast any component. is a feedback taken care- of in the design.
Thank you.
parick says
Good day sir
please how can i give the above circuit a feedback loop to maintain the output voltage? Thanks.
Swagatam says
Parick, all the first 3 designs include an automatic feedback…
Adeyemi says
Thank you sir, Swagatam, for your educative site. Please I made a 3.5kw inverter with 72v battery input using 1 pair of high capacity mosfet of 600v and worked perfectly but any shake like just touching to test the voltage with meter, it blows up. Without shaking, it does not blow. All the solderings are firm. I have successfully made inverter with 36v input.
Swagatam says
Adeyemi, there could be a short between the winding of the transformer, or somewhere in the connections.
Adeyemi says
The last circuit in this page tag simpler alternative, you designed R11 1k and c5 1u differently for both, won’t this cause imbalance.
Swagatam says
You can ignore that, the diodes are enough to handle the reverse spikes, the design was referred from another source and the RC network doesn’t seem to be serving any crucial purpose
Adeyemi says
Please for 1kva inverter what is the maximum load it can carry
Swagatam says
May be up to 900 watts
Adeyemi says
I’m a bit confused, an engineer just told me a 1.2kva inverter/12v can’t power a 0.5HP pumping machine of 375watts. I don’t understand. Please sir, Mr Swagatam, help me clarify.
Swagatam says
Hi Adeyemi, I think you should request him to clarify the reason. As long as the pump consumption stays below 600 watts at full load, the inverter should be able to take the load.
Only during the switch ON the motor may consume upto 3 times more power, that could be a problem.
Adeyemi says
Please, I read that pure sine inverter (trafo based) consumes more energy than modified inverter, by what factor sir, thanks for your educative assistance, Mr Swagatam.
Swagatam says
I don’t think that’s correct, because both are PWM based designs so their working principle should be almost the same.
Adeyemi says
Please how can I earth an inverter connection properly, thanks sir
Swagatam says
You can connect the transformer lamination and the inverter chassis with the earthing line.
Adeyemi says
Please where on inverter chassis can I earth
Swagatam says
Anywhere, it is supposed to be a metal chassis so position is not critical.
Adeyemi says
Can I use heat sink of mosfets because it is already earthed with the base of the trafo lamination, I don’t know where to earth for inverter, please sir, help out rainy season is here.
Swagatam says
I won’t recommend earthing MOSFET tabs. You must earth only the negative line of the battery.
Adeyemi says
Please for clarity, are you saying I should earth trafo lamination and the negative battery line from our discussions. I am thinking it will cross react because of the heatsink which is a conductor.
Swagatam says
Do not connect the heatsink with the metal body.
Adeyemi says
Please, how is that possible because the bolts that fasten the heatsink and the trafo are conductors. Please guide.
Swagatam says
Sorry I can’t suggest on other prototypes, according to me the MOSFET should be kept aloof from the inverter body and the transformer body.
Olamide Emmanuel says
Please do u observe that the capacitor increases the noise level?
Swagatam says
No it did not create any extra noise in my experiment.
Olamide Emmanuel says
It does so 5x here I think I will change the variable resistor from 50k to 20k to see what happens again.
Secondly, I have worked with many voltage regulators e.g. LM7815, 338, 317 etc their output voltage varies with the input voltage. Please I need something that can fix output at around 14v regardless of the variation at the input. Good hysteresis and surge.
Thanks for your prompt and constant attention.
God bless you.
Swagatam says
Olamide, The sole purpose of a voltage regulator IC is to keep the output voltage constant irrespective of the input variations. If it is not doing this then either the IC is faulty or a fake one. Alternatively you can build your own customized regulator using the concepts explained in the following article:
https://www.homemade-circuits.com/simple-voltage-regulator-circuits-using-transistor-and-zener-diode/
Olamide Emmanuel says
Thanks a lot. I’ll try some of these designs. I currently have about ten used LM196 which have all gone bad. Most of the importers here bring components that have exceeded their shelve lives. God help us.
I have uploaded the source-code you shared on arduino and it compiled and ran well on my arduino uno. Please help me the circuit diagram of the complete design so my inverter can run on a micro-controller and a single transformer or any with C51/C52 family since I have the IDEs.
Thanks, GOD bless you real good.
Swagatam says
Hi Olamide, you can buy these parts from amazon or aliexpress, they are pretty genuine. I am glad the code ran well, however, since I am not an Arduino expert, I may not be able to help you much in this field, I am sorry about that.
Mitech says
Sir, I encountered the same problem. Connecting a capacitor at the output increased the noise level and also the No-load current. why is it that way?
Swagatam says
Mitech, connecting the capacitor at the output might increase the standby current slightly, but the noise will decrease, did you verify the noise with an oscilloscope? In fact, in many modified sine wave inverters, connecting an output capacitors improves the waveform, close to a sine wave.
Olamide Emmanuel says
Well done Mr. Swagatam. Can the same process that purifies the square wave to obtain basic sine wave be used to purify modified sine wave to obtain pure sine wave for better protection for very sensitive gadgets?
Thanks.
Swagatam says
Olamide, you can use capacitors at the transformer output to purify modified sine waveform
Adeyemi says
Good day sir, please can I use 7812 regulator for oscillator input for the power supply for 12v inverter system, if I use any effect. Thanks Swag
Swagatam says
yes it can be used, but add a 100 ohm resistor in series with the input of the IC, and also a 100uF/25V capacitor on both input and output leads of the IC
Sayed says
hi swag .i simulate the spwm circuit by using orcad and i get this result:
https://1drv.ms/u/s!AmpwfsAEQtshimD216KVSdKA_c9I
as the fast triangle wave has bias and the fast triangle wave is not generated correctly the comparator cannot compare the tow wave correctly and the spwm is not created.
the blue wave is the output of the op amp
the green one is the slow triangle wave and the red is the fast triangle wave.
i used exactly your design parameters in the simulation
Swagatam says
Hi Sayed, you are right, because the two triangle waves are so different with their parameters, you have to make sure the triangle waves only differ in their frequency not with their dimensions. You will have to optimize them using an oscilloscope and by experimenting the part values of the astable. Moreover each slow triangle wave must accommodate no more than 6 fast triangles. The SPWM procedure has been also explained in the following article
https://www.homemade-circuits.com/how-to-generate-sinewave-pwm/
Swagatam says
I have only provided the basic design concept for the SPWM, not the exact part values, the part values and waveform must be tweaked with an oscilloscope
Evans mworeh says
Sorry I forgot to indicate that the same transformer and mosfets should be used for inverter and charging. At least make the circuit easy for me to analyze and construction. Also pwm should be integrated, thanks in advance.
Swagatam says
The concept of relay changeover will be exactly the same as described in my earlier full bridge suggestion.
Evans mworeh says
Sir I understand that with a 6000w inverter,more than 240A will be drawn from the battery,now my question is is there a relay that can handle such huge currents?
Swagatam says
You can search it online….or use an equivalent SSR.
Evans mworeh says
Hello sir swagatam,I have a 2200w rated refrigerator,a 2200w rated microwave oven ,4×65w fluorescent lights. Please I would like you to help me with an Inverter circuit diagram either using CD 4047 or sg3525 H-bridge that can run a refrigerator and be able to run also the other appliances which totals to about 6000w. Also the Inverter should have a feedback for low battery cutoff and battery charging system. I have a two wire (non centre tap) 6000w transformer,2×12*200AH batteries and am planning to use irf064 as my mosfets.
Swagatam says
Hello Evans, I have already provided all the details in the above article and also in a few other related articles, you will have learn them step wise and then integrate them to get the intended design… You must first build a small prototype and then gradually upgrade it to a more powerful version.
sayed says
hi swag, the design with the spwm can support a load above 1000 W ?
Swagatam says
Sayed, the pwm is only for the waveform, the power is determined by the transformer, MOSFet and the battery, which can be customized for any desired power
sayed says
hi swag,tanks for quick reply.i was testing the spwm stage,i built the astable 555(fast triangle wave) and i get this waveform 🙁https://1drv.ms/u/s!AmpwfsAEQtshil8otxdxMJymsU8j)
why the wave had a bias ???
Swagatam says
Hi Sayed, it’s because the IC 555 capacitor charge and discharge happens between 1/3rd and 2/3rd supply levels.
sayed says
so the comparator dont work properly in this case !!!!
Swagatam says
It will work properly and create the PWMs perfectly…
Lakew Kidane says
Found it very attractive ,thankyou
Sunshine says
Engr. Good morning..please do you have a circuit diagram that can boast my phone’s signal. We have poor network in my area thanks..I always find it difficult to browse Internet..thanks
Swagatam says
Sunshine, please post the comment under a related article, please see the message which I have put just above the comment box.
Gamini Rathna says
Good evening Mr. Swagatam,
Can I use a ferrite core transformer for this inverter? If so what should be the volts per turn?
Swagatam says
Gamini, ferrite transformers will require strict calculations as explained below
https://www.homemade-circuits.com/how-to-design-and-calculate-ferrite-core-transformers-for-inverters/
jon says
thanks for share
B K Leelesh says
Sir, I have constructed twice your first design successfully. However I want your help regarding the following problems.
1. Since I couldn’t get 330k pot I used 200K pot in series with 100k (R2)
instead of 1k resistor. Is it Ok.
2. I extended the circuit wit your battery charging circuit using lm358.
3 Now I am using 18 amp battery.
4. Now my problem is in my second attempt, the battery cables are
getting heated, with too much noise from transformer.
Pl.help me sir, What would be the problem.
Your, faithfully,
Leelesh.
Swagatam says
Hi BK,
Yes 220K will do instead of 330K
Is the inverter working OK without the battery charger? You must check and verify the two stages separately and only then join them together. I will have to see the schematic to be able to troubleshoot your problem. You can it send to my email.
The problem that you are facing clearly indicates a short circuit across the MOSFeTs, due to blown MOSFts.
JACKSON LENATUS MWANGILI says
Shalom,
For transfomer with 26.8-0-26.8, what will be the battery voltage if i design my circuit with SPWM
Swagatam says
The battery voltage can be around 36V
Jackson says
Good job brother..
I have tried to build the SPWM circuit,
The readings are as follows
1. Fast wave frequency = 350hz,to pin 3 of lm741
2. Slow wave frequency = 50 hz,to lm 741 pin 2
3. Output of lm 741 pin #6 = 50.44Hz
4. Frequency of both Mosfet gates = 25.22
5. Sg3525 pin #11 &14 Voltage is 5.3 each
6. Output frequency of Transformer = 50.33Hz
7. Transformer 26-0-26 primary /secondary 235V power of transformer is 6KVA
8. Input voltage to transformer =33
9. Input to oscillation is 12Voltage
10. Transformer sound normal,seems everything is ok but….
PROBLEM
Output voltage Multimeter reads 1.988Voltage,
What could be a reason for such low voltage while transformer is sound like everything is ok?
Swagatam says
Thanks Jackson, I would suggest you to first build the basic 50 Hz inverter without any PWM and verify its normal working with optimal loads. Once confirmed then you can try integrating the PWM for the final results. You may need a scope for this, only frequency measurements might not be sufficient to troubleshoot faults if any.
Emmanuel Offiong says
Jackson
(1)you need to put a 5kohms preset from the output of the SPWM circuitry before it get to the base of it BC557 transistors so that you can be the one to set your output voltage (ie from the transformer output) or
(2) you interchange the connection of the fast frequency and slow frequency that is getting to the opamp (ie connect the slow frequency to the point that you connected fast frequency and take the fast frequency to the point that slow frequency was connected before ) with any of this solution you will get your output voltage but the second option will not set the output voltage if want to set the output voltage you can go for feedback system or you put a preset at the output of the opamp before it get to BC557 transistors. Don’t forget to include a capacitor at the output of the transformer the value should be 185 or 155 by 400volt, I hope you know how to connect the preset if you don’t know it goes this way the right pin# is connected to the output of the opamp then the middle pin# is connected to the base of BC557 transistors and left pin# is to the ground that is all.
Sunshine says
Good morning sir…Engr. I hope you are fine.
Please I want to step down 24v DC to 12v DC 5A please help..I tried it using MOSFET and 7812v but it gets hot so quick..thanks
Swagatam says
Sunshine, linear regulators will heat up since they will be dissipating the excess voltage into heat during the conversion. You will need a buck converter for this if you wish to get it done efficiently…there are many buck converter circuits online you can find.
Sunshine says
good morning sir..thanks for answering my previous questions…engineer please I need FM radio transmitter circuits diagram…I got some in your blog but I don’t know how to increase the ranges/distance.. Frequency variation if possible. Thanks so much…
Swagatam says
Hi Sunshine, any range beyond 200 meters will require special antenna and optimizations.
You can use the following concept to get up to 200 meter range
https://www.homemade-circuits.com/homemade-walkie-talkie-circuit/
Dru says
Hey shalom…could you please help me outdru with how to interface the egs002 with the sg3525 man…
Sunshine says
Okay thanks a lot.. But sir, is there any formula regarded to this issue..for better calculations? Assume
my house total load is 800w,
inverter 1kva,
run time 8 hours.
.battery ah…?thanks
Swagatam says
Hi Sunshine, I already have an article which you can read and calculate the parameters as per your exact specifications:
https://www.homemade-circuits.com/how-to-calculate-and-match-solar-panel/
Sunshine says
Good morning sir…how do i calculate battery’s voltage and current to know the solar panels that can charge it., and how long battery can stay for inverter during using in house thanks
Swagatam says
Hello sunshine, The voltage must be at least 6V higher than the battery specs, and the current 5 times less than the battery Ah for a lead acid battery. These must be checked at peak sunshine, with no load connected. The discharge rate of the battery should be 1/10th of the battery Ah value, then it may provide a back up of around 7 to 9 hours.
Emmanuel Etim Offiong says
Good morning my able tutor please
I have another question which is how will i set the output voltage of the inverter if I’m using SPWM circuit with the SG3525 circuit
Thanks
Swagatam says
Hello Emmanuel, it can be done by adjusting the dead time value of the SG3525 IC
Sunshine says
good morning brother..Engr. I built this inverter circuit using SG3525 with sine wave conversion…is working, but the MOSFETs IRFP150N *4 with heat sink heats up immediately, if no load and when loaded. Please I need your direction.. Thanks may God reward in with good things abundantly
Swagatam says
Thanks sunshine, please replace the existing NPN/PNP BJT output set up with only NPNs, as shown in the following diagram, and then check the response:
https://www.homemade-circuits.com/wp-content/uploads/2019/09/PWM-MOSFET-connections.jpg
Emmanuel Etim Offiong says
I thought that the 1k resistor suppose to be connected in get to source in which is ground not get to positive
Swagatam says
grounding is done by the transistor. Any extra resistor across gate source will not make sense in the above linked circuit.
Emmanuel Offiong says
Alright sir thanks a lot for your support and god bless you for your good work
Swagatam says
My pleasure Emmanuel
Emmanuel Etim says
Hi swagatam
I really like your article a specially that true sine wave inverter circuit that uses the combination of SG3525 and 555timer ICs but is like the SG3525 circuit is giving high frequency and also the 555timer circuit is also giving high frequency and if so what will be the total output frequency in the output of the transformer and also i would have love to see the simulation of the wave form of this circuit
Thanks
Regard
Swagatam says
Thanks Emmanuel, the inverter output will be stabilized by the transformer which will be equal to the SG3525 frequency. You can add a few capacitors at the transformer output to stabilize the output perfectly.
Emmanuel Etim Offiong says
And also can i used pure sine wave signal generator circuit to feed in the place of PWM signal to the SG3525 BJT circuit
Swagatam says
No, It should be in SPWM form, not exponential, ….only spwm will work
Emmanuel Etim Offiong says
Okey thanks
Akinbi says
Helo sir,am having concern for my feedback.Whenever I on my inverter ,I noticed the feedback always drop,pls what can I do ?
Swagatam says
Hello Akinbi, Feedback system will not work if the load current exceeds the battery’s maximum limit or if the battery voltage becomes low. It will work only when the battery is optimally charged and the load is within acceptable limits
Onyeka says
Have not done any work at all based on your post but just going through it gives me enough vibes…..thanks boss, you’re doing a great job🙌
Swagatam says
Glad you liked them, wish you all the best!
Tolu says
Please between using rectifier at the inverter output and rectifier at mosfet line to send feedback to pin 1 of sg3525, is better for automatic voltage regulation
Swagatam says
From output is better, and should be through an opto-coupler
Tolu says
Please how can i use optocoupler circuit, any circuit
2. From 3kva Anas’ circuit, for pin 11 &14 10k resistor connected to the ground, what is the relevance, and is it necessary
Swagatam says
It’s a good practice to add grounding resistor across base/emitter of any transistor. where do you want to add the opto?
Tolu says
Please what is the likely standby current draw for a trafo based and trafoless 1kva inverter. Thanks
Swagatam says
A trafoless inverter will have negligible standby consumption compared to a transformer based inverter
Tolu says
Please what can i do to the sg3524 ic i use, yearly during raining season, it usually develops fault due to lightening, and thunderstorm which i replace.
Swagatam says
Try connecting the inverter body with a good earthing connection.
Mathieu says
Hello Swag deos the SG3525 can work with a 7809 voltage? my sg3525 cant work under 12VDC!
thank you!
Swagatam says
Hi Mathieu, SG3525 will work with 12V and also with 9V, something may not be correct in your circuit!
D K Mishra says
Dear Swagat,
I tried the basic circuit with a salvaged trafo of my ups, 4XZ44 mosfets and 7AH battery. The osc frequency is 51hz,50%duty cycle. Driver is Pnp/npn pair as per Yr circuit schematic.
But the mosfets blew up.
Checked the ckt and replaced the mosfets.
Now powered through a series bulb 21w,12v and circuit worked with 185 V out put. Loaded a 9w led bulb and it worked. Voltage drop at bulb was 6v. Connected 2 freewheeling diodes too. But when direct powered, the mosfets blew again.
Pl advise. Is there any snubber issue?
Swagatam says
Dear D K Mishra, MOSFETs can be very unpredictable and can blow without apparent reasons.
You can refer to the following article, and possibly apply all these protections to your MOSFETs:
https://www.homemade-circuits.com/mosfet-protection-basics-explained-is/
By the way what is the specifications of your MOSFETs? I tried to find the datasheet of 4XZ44 but could not find any…did you mean IRF44Z?
Alternatively instead of MOSfETs you can try a combination of TIP122 and TIP35 BJTs which will never blow unless the base is shorted to positive line.
Victory says
Hello creative Engineer please how can I have stabilised voltage regulator for my oscillator at peak sunlight because there is increase in voltage at pin 11 and 14 which causes output voltage instability of the inverter. I have used zener, transistor, 780x as regulator but not difference .
Swagatam says
Hello Victory, 78XX will definitely stabilize the voltage to the oscillator and its frequency. The output may be increasing due to increase in peak voltage to the transformer, which you can control through a feedback control system.
Bogdan says
the day, I did the inverter from the last schematic and I have a very disturbing noise at the transformer, is it normal? which would be solving for less noise?
Tks
Swagatam says
Do you get the noise without the IC 555 PWM?
Bogdan says
I did not try without 555 am
loaded directly with 555 and 6 transistors for a pure wave inverter,
I tried an electric motor and it sounds the same sound.
Swagatam says
Disconnect the IC 555 PWM link from the BC547 transistors, and check whether the sound still occurs or not?
Bogdan says
can I get only 555 from the socket or should I give up 10k resistors of pins 11 and 14 and to connect the mosfets directly from sg?
Swagatam says
If you have used a socket for IC 555 then removing from the socket will be enough
Joseph says
Please, can you give me the full circuit with H bridge with oscillator like sg3234
sayed says
hi swag, i built the 3rd circuit (the one used in pcb) without the pwm stage.and i get this output
https://1drv.ms/u/s!AmpwfsAEQtshgnPpqeCDab6Ivu_Y?e=3zSG8j
where is the problem?
Swagatam says
Hi Sayed, it will be difficult to guess because the 3rd circuit is a tested design and a standard 3525 circuit. Please check the waveform across the output pin of the IC, it should be perfect rectangular waves.
sayed says
hi swag ,thanks for your quick response.the waveform across the output pin of the IC is showed in this link:
https://1drv.ms/u/s!AmpwfsAEQtshgnQom2w4J8HWeepG
Swagatam says
Hi Sayed, it looks perfect, the output may have harmonics and that’s why it may show some interference. You can connect a 2uF/400V capacitor at the output and check again
sayed says
Hi swag,with 2uf capacitor at the output ,the output waveform looks like this:
https://1drv.ms/u/s!AmpwfsAEQtshgnVdP0sNbxAWeKJD
Swagatam says
Hi Sayed, it looks much better now!
sayed says
yes looks better but with high p-p voltage!!
Swagatam says
The peak will depend on the winding of the transformer. It should match the RMS or the average PWM produced a the MOSFET drain. If suppose trafo primary is 9V, and the RMS is 10V, then output will not be 220V, it will be 244V
sayed says
i build the circuit without the pwm stage and i used a 12-0-12 trans
Swagatam says
You can decrease the output peak by adjusting the PWM
Frank says
Hi Swag thanks for the wonderful work.
I intended using it for battery charging also but the transformer voltage is lower than the battery.
Please help.
Swagatam says
Hi Frank, are you using a center tap transformer for the inverter? in that case you can use the outer wires of the transformer for the battery through a regulator.
MITECH says
I got same waveform at no load using oscilloscope. On connecting a load, the waveform will change to a Better shape.
Victory says
Please sir, why is important for transformer output to give about 310v before voltage correction. At times my trafo output could be 270v before correction
Swagatam says
Victory, it is to ensure a plus margin for the feedback regulation. 270V is also OK although it may provide lower range of feedback stabilization.
osei kwame says
Hi teacher Swagatam I want you to check this for me please
if the 741 cut off is base on input low voltage then
what will happen if using 24v and 7812 for driver circuit? how would you configure the 741 under this teacher because the 7812 will also Serv as steblizer if even battery voltage should drop to 16v
the 7812 will still maintain the 12v out put to the driver circuit and also the 741
Swagatam says
Hi Osei, to solve the problem quickly you can use LM321 or LM358 which are rated to work with 32V.
For 741 supply the 7812 only to the pin#7 of the IC, the inputs can be directly connect wit the battery supply. For the inputs use a 10K for the zener diode, and 10K in series with the preset, this will ensure that the input pin never gets 12V while adjusting the preset.
Osei Kwame says
Thanks for your quick response
If I understand you teacher,
741 pin 7 to 12v and the inputs configuration can be contacted to the 24v per my power is this ok teacher?
If I should go for 321 then pin 5 can link the 24v per my power and the remaining configuration remain the same ok teacher ?
Thanks teacher.
Swagatam says
yes that’s right, just make sure to add 10K in series with the positive side of the preset for IC 741
Osei Kwame says
I hear you teacher and thank you very much.
Osei Kwame says
Sir Swagatam my greetings, I was away for sometime but I’m back and I just missed your teachings thanks teacher.
Swagatam says
No problems Osei, please keep up the good work!
sayed says
hi swagatam , which circuit is fully tested that i can use it?
Swagatam says
Hi Sayed, all are fully tested you can choose anyone as per your preference.
sayed says
hi swag, i built the 3rd circuit (the one used in pcb) without the pwm stage ,the frequencies of pin 11 and 14 was not 50hz , i changed rt and ct to get 50 hz and i get tow nice square waves from pin 11 and 14 ,but when i add the mosfet stage ,without any load the mosfets explode.
I added a 0.33ohm resistor betwen the drain and the trans end , the circuit worked and i get in the output a wave similar to square wave (with some overshoots) with 400v p-p voltage and 186v Vrms
and the 0.33ohm resistors get hot quickly where is the prob?
Swagatam says
Hi Sayed, MOSFET behavior can be tricky to predict. You can read the following post to understand how to protect it from various situations:
https://www.homemade-circuits.com/mosfet-protection-basics-explained-is/
You can employ the procedures explained in the article. The 0.33 inclusion is not correct as that would prevent the inverter from operating in normal conditions.
sayed says
so the circiut that i used can works properly without the pwm or spwm stage?
and check the rt and ct value in your post cause with that values the waves generated are not 50hz
Swagatam says
PWM or SPWM are optional stages which allows us to get better optimization of the output, you can avoid them if you wish, and make an inveter using basic SG3525 circuit. You can tell me the Rt/Ct values, I’ll mention them in the article.
Taurai Mirimi says
Great designs. Great ideas. Thanks
Swagatam says
Thank you!
Faith says
Good day sir please sir my inverter feedback is not working when ever I connect load to it the output voltage drop I check the voltage at pin 1and 2 of my sg3524 it 5v and 2.4v respectively please what could make the feedback not to work
Swagatam says
Faith, if the load wattage exceeds the transformer or the battery wattage then the feedback control will fail to work, please confirm this!
Harun says
How to calculate MOSFET in pallarel or how to know number of transistors that will give me 1500w for inverter
Swagatam says
Multiply the IDS and VDS of the individual MOSFETs, and add them, this will give you the maximum tolerable power of the MOSFETs combined. Make sure the margin is at least 10% higher than the required power output.
MITECH says
The feedback can work well when you use a transformer that can give output voltage that’s more the output you want the inverter to give without connecting the feedback yet. Let’s say Your transformer gives 250v above without feedback then when u connect feedback, u can now scale it down to 220V but if your transformer gives 220v without feedback, on connecting feedback there will be no regulations unless you need voltages that’s below 220v.
Swagatam says
If the load exceeds the transformer wattage, then the feedback won’t work and the output voltage will drop below 220V, no matter how much excess margin you may have.
osei kwame says
Hi teacher Swagatam, is it possible to apply full bridge to any of the circuit provided especially the SPWM inverter circuit . Teacher what should be the way to go about it if possible
I have started working on SPWM and I will alert you the outcome
thanks teacher
Swagatam says
Hi Osei, it is possible, you can chop the low side MOSFETs with the SPWM. you can see the example in the second circuit below:
https://www.homemade-circuits.com/5kva-transformerless-inverter-circuit/
In the first circuit you can apply the SPWM to the 4N25 opto transistor base
Osei Kwame says
Thank you teacher
Faith says
Sir that’s exactly what I did the inverter work well no heating nor noise but frequency is high not 50hz as expected so my question is what
Frequency range should I expect
Swagatam says
Please measure the frequency at the output of the transformer, it must be equal to the slow triangle wave frequency or the frequency at pin#4 of SG3525 (50 Hz). The fast triangle wave frequency can be around 400 Hz.
osei kwame says
Hi teacher Swagatam i was looking into the modefied circuit posted by Lynch which I think is from your 3kva inverter circuit . l could see many changes in his post . please explain this to me.
1.what is the name and function of the parallel circuit in series to the 100uh to 12v supply voltage.
2. 100 instead of 470 ohms between pin 5 and 7.
3. two 10k between out put pins 11 and 14 to ground also omitted.
Teacher, what significant changes does it bring to the function of your 3kva circuit
4.10k from pin 2 to ground omitted.
5.function of capacitor connected to pin 9 and ground
can this circuit also work under 12
to what supply voltage?
and if I want to go from 3 to 10kva what
changes should be made
6. spmw and pmw which one is more efficient
Swagatam says
Hi Osei,
The inductor is for suppressing interference from the transformer into the circuit to ensure the circuit works smoothly.
The parts at pin7 and pin5 decide the frequency, different combinations can be used for getting 50 Hz.
the 10K are not compulsory, but you can use them for increased safety of the mosfets. They have nothing to do with the 3kva function.
Pin#2 is the non inverting input of the internal error amp, which needs to be supplied with a reference voltage, the 10K is probably included to adjust this reference value.
Pin#9 is not crucial, it is for introducing hysteresis for the error amp, and can be ignored.
Maximum operating voltage of the IC is 35V.
SPWM is more efficient
Osei Kwame says
Thanks teacher for your quick response. So if i use the circuit posted by Lynch I can still run 3kva to 10kva ? .
Teacher if I want to go for high power then the changes should be on the transformer, battery and fet transistors leaving the driver circuit as it is .
Is that ok teacher?
Thanks .
Swagatam says
That’s correct Osei, you can use any of the designs for getting any desired power output, just by upgrading the three elements.
Sigifredo Cruz Rojas says
Hi
the SG3525 that comes from various cheap inverters on ebay control the output power by adjusting the duty cycle of the mosfets right?
I ask that because when I measure the signal on the mosfet’s gate I see full dutycycle even when there is no output connected and the input current is almost nothing… what Im missing???
I always suppose that u control the output with the DC of the mosfets but as I see that is not the case with the SG3525….
Swagatam says
Hi,
The duty cycle can be adjusted either by a variable resistor at the respective pin, or through a feedback from the output.
So it will depend on the above two factors. If you have a variable resistor at the PWM pin, then you can vary it and check the results.
MOSFET drain current can be efficiently controlled by PWM control and not by linear DC levels, because lowering DC at gate can heat up a MOSFET
Sigifredo Cruz Rojas says
thanks but why the duty cycle is the same with full load and with no load?
Sigifredo Cruz Rojas says
all the current pass inside the SG3525 ???
I have monitor the gate signal of the Mosfets with a Oscilloscope and it is the same with or without load….
Please tell me it is an error to replace a 60v/120A mosfet on a inverter with another mosfet of lets say 500v/120A?
Swagatam says
there’s nothing wrong, but MOSFET rating ideally should be as per the battery specs, otherwise the energy conversion will not be efficient.
Swagatam says
It will be the same unless you apply a feedback circuit from output to pin#1, as shown in the following first two diagrams:
https://www.homemade-circuits.com/sg3525-pure-sinewave-inverter-circuit/
Sigifredo Cruz Rojas says
thanks for the answers… I see so if u are using 12v batteries it is obvious that u need near 12v mosfets… 500v mosfets have much higher internal resistance making it less deficient…
It is my mistake not to clarify that Im talking about the circuit on a cheap aliexpress DC-DC step up module.
I suppose that after the mosfets there are additional transistors that allows current to pass controlled by PWM that use the output feedback… I see a MCR100 near the end bridge rectifier… it is tiny but controls up to 600V… I suppose they let the mosfets with a constant full DC and controls the output with that SCR.
Very cleaver but I wonder if it is better than just change the DC on the mosfets gate.
Swagatam says
Can’t say much about it! It will be difficult to suggest without seeing the full schematic diagram of the circuit.
Andrew says
Hello my teacher, my appreciation 2 u 4 your good works and support, I just finish building 1000w which is 1kva from this your nice circuit and it’s working perfectly well, i use a 2000w transformer 12v- 0 -12v IRF540 x4 and am using 75ah x2 batteries and the ouput is very stable and it’s handling 800watts of load from my calculations and when the 2 battery’s his fully charged it only gives me back up of 2 hour 30 to 2 hour 45 minutes and i only make use of it in the day time which means i do not need a reserved better because i closed 6.00pm everyday, please teacher i don’t know if it’s possible to get a solar panels that can back the load of 800w without having to charge the battery with generator, if yes, how many panels and which Watt’s should i go for? Please sir i really need your help because there’s no electricity here and i waste a lot of money to ⛽ fuel my generator. Thanks my regards.
Swagatam says
Thanks Andrew, I am glad you could make it successfully.
800 watt solar panel is possible. Calculating solar panel is actually very easy, if you read the following article you will be able to calculate the right panel as per your available specifications
https://www.homemade-circuits.com/how-to-calculate-and-match-solar-panel/
Let me if you encounter any doubts.
Andrew says
Thanks 4 your quick respond, i now understand how 2 choose the right solar panel, battery’s charger controller and lot more about all the calculations, please keep up d gud works and thanks once more.
Swagatam says
You are most welcome Andrew, please keep up the good work!
Glory says
Good day sir, I have built 1kva,please I wanted to build a 200va trafo based inverter(modified). I used a 7Ah battery, the trafo coil guage was G20 swg for both primary and secondary. The max output voltage was 80V with load, with 60w loa it dropped to 28V. Please advise on what to do and the causes of low voltage
Swagatam says
Glory, Both side winding can never have similar wire gauge. It will be according to the current of the winding, consult a transformer designer!
Christ bride says
Please sir I need a simple schematic diagram of 3kv inverter, because that one in this post have 2 diagrams and it is confusing me.
Swagatam says
Christ, You can try the following circuit:
https://www.homemade-circuits.com/48-v-inverter-circuit/
Andrew says
Hello teacher, first let me say a big thanks to you, Three ★** 4 u👌 I build #3design 3kva without any problem, i use x10 IRF540N 48V 0 48V transformer 12v 100ah battery x4 but i don’t know how to calculate how many MOSFET i should use. Please teacher i want to know if i could build a smaller watts like 300w, 500w to 1000w and how to make the change, if it can be done, what should i do?
Swagatam says
Glad it worked Andrew, that’s wonderful!
You can definitely smaller versions by using just a single mosfet instead of many in parallel. Please read the following article, it has all the details regarding the calculations required for selecting the mosfets for a desired load.
https://www.homemade-circuits.com/how-to-calculate-and-match-inverter/
selemani tz sikonge says
Thanks for more diagrams can i buy pcb circuit (sine wave)from you now so how can communicate to you cause i need pure sine diagrams with sg3525 chip thanks
Swagatam says
Thanks selemani, glad you liked my diagrams, however I am sorry presently I am unable to provide PCB designing help due to work load, I hope you will understand!
Sunshine says
okay sir pin 11 =6.03v and pin 14 = 6.03v,,,,do you meant that I should make the transformer primary 6-0-6 and the secondary output 220v? I already made my transformer 9-0-9 and 0-220..I want to make 1000w inverter…
Swagatam says
Sorry Sunshine, there’s a slight confusion. Since duty cycle is 50% for each cycle, 6V corresponds to 100% duty cycle for each output, for a 12V battery….so your trafo should be 12-0-12V, but 9-0-9 is also OK.
Now make sure the current of the battery side of the trafo is high at least 10 amps.
Kayode says
God bless you abundantly sir for your I have built this circuit 3 times without any problems, but I’m building another one and if I reduce p2 it gives voltage of about 100v but if I increase it it damage 3525 and if I pls sir I need your help.
Swagatam says
Thank you Kayode, can you please show me exactly which 3525 circuit are you building?
P2 is only for setting the reference value for the error opamp (which has a high input impedance), it cannot cause any damage to the IC. It seems your IC is duplicate or is a faulty one.
Kayode says
tnks for the response my tutor, what i noticed is that even when all the connection and callibration of the inverter parameters is done and the inverer is working ,when i remove the battery terminal and put it back ,it sparks and when it sparks the sg3525 is dead, replacing it againg the inverter starts to work. im just kind of confused, i added an electrolytic cap to filter the input to the osc and increased the gate resistor with 1k ohms in series with each signal from#11 and #14 it gives better results but i doubt its good functionality because of the way i see its differnt from others i did, but maybe its the ic. ill change it sir, also the auto regulation principle is a litle bit confusing because i did it and its auto reg was about 10% efficient, pls sir can you ellaborate on the auto reg? tnks and god bless you
Swagatam says
Hi Kayode, connect the supply voltage to the IC through a 100 ohm 1 watt resistor, and make sure to connect a 100uF/25V across the supply pins of the IC, and also add a 12V 1 watt zener across these supply pins. this will prevent your IC from blowing repeatedly.
Kayode says
Tnks sir, I’ll do that and give you the feedback ,
1. Pls must the c1 be mkt type or can we use the ceramic disc type?
2 pls is the auto correction for maintaining the set value so that it doesn’t go beyond or below n because , I don’t have a stable voltage, it drops while increasing load, to about 170. . Pls what do I do to get a stable 230v.?
3. The output of the 741 ic shuts down the 3525 gradually thus making the output of the inverter gets lower slowly till it dies, I have used the 4007 diode forward bias to the 3525 #10, all is about the first design, tnks sir, awaiting your reply .
Swagatam says
Kayode,
1) C1 should be MKT preferably, although ceramic will also work.
2) If your output is decreasing with load, it means your battery current is insufficient to handle the load. The auto correction can never increase the output. The auto correction can keep the output constant only as long as the load is within the battery limits.
3) The operation is correct, the output will go down slowly when pin10 is held high continuously
Anthony says
Hello sir, pls under circuit design one, you posted another circuit with automatic feedback control with the title “Another Design with Automatic Output Feedback Correction” just before the begining of the explanation of circuit design 2. All I want to ask is that can we use the feedback control mechanism they used there in any sg3525 inverter circuit for the feedback control.
Like the sg3525 inverter diagram I have I connected the 4 diode bridge rectifier across the transformer as they did here and from the first wire of the rectifier I connected 5mh which went to 10uf capacitor and from the capacitor to the ground, also from that same wire from the rectifier I connected 56k Resistor and 1k Resistor, the subsequent wires from the 1k ohm went to the first pin of the sg3525 of my Inverter and to ground, the remaining wire of the rectifier went to ground. Also the the ground here does it mean to the negative side of the 12v battery. Pls will this arrangement work for my inverter and any sg3525 inverter as regards to feedback control. Thank you.
Swagatam says
Anthony, all the ground symbols refer to the negative of the battery, so you must join all those wires together, and connect the negative of the battery to the SOURCE terminal of the mosfets. You must connect the feedback system exactly as shown in the diagram, it will work. In place of 56K you an use 100K, and in place of 1K you can use 2K2 resistor for better safety.
Anthony says
Thank you sir for the reply
Sir pls can I use this feedback control mechanism in any inverter or only in sg3525 inverters
Swagatam says
No problem Anthony, you can use the op amp feedback circuit with any and all inverters provided their output devices are N type.
Sunshine says
good day sir,, engr. I built the 3rd circuit above..there is output voltage from ic, I connected MOSFETs with 12v ups transformer but the output voltage from the transformer can’t power any load,,, okay I made the battery 24v it powers 100w bulb if I put another load the voltage comes lower pls help..my battery is okay…
Swagatam says
Hi Sunshine, please measure the DC voltage at pin#14 or pin#10 with respect to ground. The transformer primary rating should be ideally equal to this value. Randomly changing battery or transformer can damage something in the circuit. Also the current delivering capacity of the transformer should be high, above 10 amps.
eric says
good evening sir, thanks for your post, please sir , I built the above inverter I mean that of Anas though I used all the modifications built when ever I connect transformer the MOSFETs get heated immediately, I have damage lots of MOSFETs and I have checked for errors but can’t fine any, though I didn’t consider the resistors wattage. I used20k preset instead of 22k, 50k instead of 47k and I used a 650 watts ups transformer and irf3205 MOSFETs please I need your help
Swagatam says
Hi eric, please try the 3rd circuit in its basic form, once its working is confirmed then you can upgrade the mosfet stage with the BC547/BC557 stage and more parallel mosfets.
If still the mosfets burn then the problem could be somewhere in your circuit layout.
Resistor wattage or slight preset value changes should not have any effect on the working of the circuit
Seun says
Please, is waveform different at different inverter voltage output.
Swagatam says
It may vary a little at different voltages.
Sunshine says
Good morning Sir…thanks for your regard, question about the transformer, I’m using 200w super Master stabilizer’s transformer,guage20 for 220v o/p side and guage12 for I/p side…..should I wind the input side 9-0-9. OR 12-0-12..and separate winding for the battery charger like 18v…for 12v Inverter… Or can you direct me here, like the turns for primary side and secondary, what wattage could such transformer give? Thanks Please don’t be upset for my disturbance.
Swagatam says
Hi Sunshine, the winding for inverter operation can be 9-0-9 for a 12V battery, for the charger you can add a separate 0-12V winding, having 10 times lower current specs than the battery Ah rating.
Sunshine says
Thanks so much I really appreciate.. God bless you..i will try this with the pure sine wave conversion system…I like your company..
Swagatam says
You are welcome!
Sunshine says
Okay thanks.. Please help me with any good inverter circuit that can power small refrigerator.. May God reward you with good thongs
Swagatam says
You can try the second design from this article, this is an universal high quality sine wave inverter suitable for all appliances.
https://www.homemade-circuits.com/arduino-pure-sine-wave-inverter-circuit/
Sunshine says
good morning Sir… u have not replied my text..
good day ENGR. thanks so much for your love and help…. I built the Inverter u Posted using SG 3524 pwm…is working the output voltage 220vac but is not stable, if I vary it sometimes it will be stable sometimes it will be blinking… what could be the issue?…. please I want to build Inverter that can power refrigerator…which circuit can I use please help..thanks so much my regard to your company friends and families.
Swagatam says
Hello Sunshine, if the output is fluctuating rapidly then there could be some problem with the configuration or one of the components, it can be difficult to troubleshoot it without a practical testing
Ade says
Hello my friend, I build one of your inverter circuit with 4047 ic. And it works perfectly. I want add this feature that will switch off the inverter when battery is drain to 9 or 10 volts.
Swagatam says
Hi Ade, you can try the last circuit from the following article:
https://www.homemade-circuits.com/low-battery-indicator-circuit-using-two/
Grace says
I meant any way to use the freezer with the 720w panels and bad 36v batteries and the inverter. I even used stabilizer with it, still it didn’t work
Swagatam says
you will need a mppt or a buck converter controller, then you use the panel directly with the inverter
Grace says
I use pwm charge controller, please how is mppt better, I live in the tropics and at peak sunlight, I get about 13amps. Please explain
Swagatam says
MPPT will try to keep your output IxV as close as possible to the input IxV, you can also try a buck converter flyback type
Grace says
Thanks creative Engineer, please give me a circuit to mppt and buck converter. I enjoy your educative site, thanks.
Swagatam says
Thanks Grace, you can try the following design:
https://www.homemade-circuits.com/5v-pwm-solar-battery-charger-circuit/
TCWS says
sir i have a modified sine wave driver using 555 and cd4017, i want to build a inverter with my transformer 1000va single 12v with 220v. what circuit do i use and how many mosfet to use. thanks
Grace says
Thanks sir for the reply. What of if I increase the number of panels with the pwm charge controller. Will it work with my freezer.
Swagatam says
I cannot tell until I know how your PWM controller is designed to work? Is it a buck converter or just a simple duty cycle based design??
Grace says
I meant factory made pwm solar controller.
Swagatam says
what is the output and input voltage and current specs of the controller?
Grace says
36v/30amps pwm charge controller
Swagatam says
Again, if it’s a buck converter then you can use it. Meaning it should be able to convert high voltage/low current from the series panels to low voltage high current for the inverter
Grace says
Hello sir, I read an article about rural mini-grid solar project in my country, and the claim was that it will be used by households with Electric stove and many heavy loads. To pay using prepaid meters,
I want to ask is it sustainable with heavy loads,
2. Can it be cheaper and cost effective than cooking gas.
3. Is solar system cost effective for heavy loads than utility.
Swagatam says
Hi Grace,
Initially the setup may look too costly, but in the long run it may pay off. But it may take at least 5 to 10 years to actually recover the initial cost.
Grace says
Thanks Chief Engineer, please how this inverter circuit do power factor correction.
Swagatam says
Hello Grace, PFC is not included in these designs, these are just basic inverter modules.
Grace says
Please any circuit on PFC.
Swagatam says
It will require some complex calculations, I have not yet investigated this subject so can’t suggest much. Here’s one article which you can refer:
https://www.homemade-circuits.com/power-factor-correction-pfc-circuit/
Grace says
Thanks for the circuit, does PFC in inverter important, your advice
Swagatam says
If you want to use it at home then it’s not important, but for manufacturing or commercial purposes it is very important.
Grace says
Sir, For manufacturing, do you mean, mass production of inverter for sale or what. Also, what do you mean by commercial purpose. Thanks
Swagatam says
It means not for your own personal use but for the masses or a 3rd person (for sale)
Grace says
Thanks for being resourceful sir. Please presently I am using 36v/2.5kva inverter with solar panels, which used to carry my freezer, but now the batteries are bad, is there anyway I can still use the freezer, only my fridge is working, I am totally off grid.
I have tried using your triac circuit for inductive loads, not working.
At peak sunlight, still not working. Freezer is new
Any advice please.
Swagatam says
Thanks Grace, Can you please specify your exact requirement? Are you trying to control 36V with a triac? Triacs will never work with DC.
Love says
I meant how to build 120v/10kva inverter using 10batteries. Most importantly the smps power supply for the oscillator section, stepdown 120v to 12v for the oscillator
Swagatam says
If you are using 10 batteries in series then you must be getting one positive end and one negative end from the series connection? You can take the positive from the battery which has its negative as the ending terminals and use this battery’s positive for your circuit.
See the battery series at the top side of this image…see how the positive is extracted from the left end of the series for ICs:
https://www.homemade-circuits.com/wp-content/uploads/2012/05/transformerlessinvertercircuit.png
Love says
The standby current draw from my 2kva inverter is 0.68amps, please what will be likely standby current for 10kva inverter
Swagatam says
As per calculation it should be 5 times more, around 3 amps
Love says
Hello sir, please what are the factors affecting inverter standby current draw
Swagatam says
It will depend on the inverter design, some may have automatic systems for switching ON the inverter only when a a load is connected, but normally It is supposed to be only the oscillator circuit, transformer primary and the relays if any!
Love says
Good day sir, is possible to build 3kva/120v Inverter. Any drawbacks
Swagatam says
Do you mean 120V DC input or 120V AC output?? If its DC input then its’ great, higher voltage means better efficiency.
Love says
Please how can I make a voltage stepdown for a 120v/10kva inverter oscillator
Swagatam says
Please provide more info!
Love says
For the back emf, why didn’t it affect the utility supply
Swagatam says
utility supply do not work with circuits, they come from generators.
Love says
Thanks for the advice, which one is electronic section,
Swagatam says
the oscillator section which creates the 50Hz.
TCWS says
hi sir swagatam, i want to built a project inverter using 555 and 4017 with a transformer of single 12v/220v rated 1000va, do you have any circuit what u call them full bridge or h bridge circuit. thanks
Swagatam says
Hi TCWS, If you want to make a full bridge inverter then using a specialized driver IC is most recommended. Using IC 555 and 4017 you can only build a center tap based inverter, not a full bridge.
You can read this article:
https://www.homemade-circuits.com/simplest-full-bridge-inverter-circuit/
TCWS says
thank you sir, may i ask? how about the article you post about the SG3525A with a full bridge power schematics? i have read it. is it possible to implement? or have no choice but to use the the recommended ICs. i have a EGS002 pure sine wave driver. thanks
Swagatam says
Hi TCWS, I got the design from one of the forums, I have not tested it practically. Therefore I won’t recommend it to a newcomer. The full bridge drivers are foolproof and therefore there’s minimum risk in using them.
Love says
Good day sir, when I put my fan(50w) to speed 1 and 2, it works fine with inverter(2.5kva), but at speed 3 the inverter blew. But speed 3 is working fine with public utility, please what could be wrong
Swagatam says
Love, what is blowing in your inverter, is it the mosfets and the ICs? Then it could be due to high amount of back emf generated by the fan.
add some capacitors 3uF/400V or similar across the output winding of the transformer.
see video in this link: https://www.homemade-circuits.com/1500-watt-pwm-sinewave-inverter-circuit/
Connect the electronic circuit section through a 100ohm resistor, and add a 1000uF capacitor after this resistor with ground. Add protection diodes across mosfet drain/source….add 1K resistor across gate source of the mosfets
Love says
Is it 1000uf or 100, as seen in video, please how does this function to prevent back emf
Swagatam says
That’s a filter capacitor 2200uF for filtering interference and spikes not for back emf.
Love says
Thanks, please is it the MOSFET diode protection handle the back emf.
Swagatam says
Yes it will!
Love says
https://electronics.stackexchange.com/questions/233394/how-can-i-protect-my-mosfet
Please which diode, type and value, can I use in the third diagram in this link, for drain-source and gate-source.
Swagatam says
You can use a 12V 1 watt zener diode for the gate
Love says
Thanks, what of the drain
Swagatam says
Drain already has an internal diode, still for extra safety you can put one 1N5408 externally
Love says
The max amp for in5408 diode is 3amps, can it handle high current.
Swagatam says
which circuit are you referring to?
Raymond Michael says
Hi Swagatam,
Longtime friend,
This article is well presented, though I have different but related request, I want to build an inverter using the same chip sg3525 but I’m using ferrite core instead of iron core, using basic circuits I manage to get 210ac at 30kHz, how can I use another Sg3525 to get 220ac at 50Hz!?
Preferably with automatic output voltage regulations.
My regards to you all.
Greetings from Tanzania 🇹🇿
Swagatam says
Thank you Raymond, using another SG3525 might not work, you will need a full bridge driver circuit for this as shown in the first diagram from this article:
https://www.homemade-circuits.com/2017/10/5kva-transformerless-inverter-circuit.html
Love says
Good day Sir, please what’s the function of lower bc547 transistors
Swagatam says
It’s for chopping the mosfet gate frequency into smaller blocks, so that the RMS waveform of the output can be set appropriately
Love says
I checked the THD of the inverter design using analyser, I got 8.8% as compared with 2.5% of the utility. Can I call it pure sine wave or what.
Swagatam says
what kind of waveform are you getting?? If you can optimize a correct waveform and make it close to the utility waveform then the THD will also improve. You can do it by adding LC filters at the output
Love says
Thanks sir, please what is the relevance of the THD 8.8%. I have used LC filter.
Swagatam says
Love, you will have to confirm the waveform first. If you are able to get a clean sine wave then the THD will be minimum. By the way it may not be fair to compare a homemade inverter with utility power, homemade inverter will always have a relatively higher level of THD.
Love says
Can we compare factory-made inverter with utility power supply
Swagatam says
yes to a great extent!
Francis says
Sir i got a 200w inverter wich usins sg3524 i modified it by hooking up the feedback for rms correction. The problem is when i connect a 16w led the output voltage drops from 220 to 212 if i increase load it keeps droping. Without load if i increase input voltage the output is not increasing meaning its only working on overvoltage not on undervoltage. Does this ic feedback work on voltage drop or am missing somethng. I know schematic is worth posting but dont have it.
Swagatam says
Hi Francis, what is the Ah rating of the battery? Please check with ammeter the current consumption of the system by connecting in it series with the battery positive, also check whether the battery voltage is dropping or not. If the battery voltage is dropping will indicate that your system is drawing over current, or your battery is not good, and this may be causing the output to drop.
Feedback will not work for over load or over current situation if it exceeds the transformer or battery limits.
Blessing says
Hello Sir, please I have an issue with my inverter automatic voltage regulator made 7 months ago using an optocoupler. The issue is that for a week now it’s not regulating well any longer, I have to reset it manually, it may work fine for two days then I reset it again. I have tried replacing it but same result. Thanks .
Swagatam says
Blessing, which schematic have you used? please show me the circuit diagram or the article link.
Abbey says
good day sir. I have problem with my SG3525A inverter feedback. my feedback is from the output of the transformer, through 280k resistor, through a diode, through one leg of 50k VR to pin 1. before I connect the feedback, the output voltage was 220v. but after I connect the feedback, the output voltage reading comes down to 0v with the inverter making a tickle tickle sound( though not loud). I tried adjusting the VR but the voltage does not respond. Pls help because I need this output voltage stabilizer seriously.
Swagatam says
Abbey which feedback connections are you referring to? Is it from the first circuit, at pin#2?
Blessing says
Hello, I used a transformer of 12-0-12v rating to design an inverter using your 555 pwm model with Sg3524 ic, I thought I would get above 300v output at the transformer but I got 220v. Is it normal.
Swagatam says
Please check the DC voltage at the gate of the mosfet, your transformer must be rated at this voltage to get 310V out. And preferably this DC level must be be equal to battery voltage divided by 1.41.
Abbey says
good day sir. thanks for your previous response. sir, can I use sg3525 square wave inverter to power a freezer. will it have any bad effect on the freezer? thanks.
Swagatam says
Good day Abbey, it may work but may cause noise, therefore modified sinewave or pure sinewave is recommended.
Abbey says
thanks for all your reply . I think I am learning. sir, I used a 5000w stabilizer transformer to build sg3525A inverter using 6 irf260 in all. how can I know the power of my inverter. I only have digital and analog multimeter. can the output be up to 1500w?
Swagatam says
Abbey, if it is a 5000 watt then you must get 5000 watts from it, you can check it practically by connecting appropriately rated loads to the inverter and check whether voltage drops or not, the load should work without dropping the voltage by much
Abbey says
sir, I don’t understand your last statement” MAKE SURE YOUR TRANSFORMER ALSO IS RATED AT THIS 50% LESS RATING AT THE PRIMARY SIDE”. Pls can you explain better? thanks.
Swagatam says
Abbey, if your battery is 12V, the mentioned DC at the output pins should be around 6V, so the transformer should be a 6-0-6V
Swagatam says
The correct value should be 12 / 1.41 = 9 approximately. So adjust the PWM to get 9V across the output pins of the IC, and select a transformer with 9-0-9V rating at the primary side.
Abbey says
thanks sir. Pls I will I know I have adjusted the PWM pot to modify sine wave since I don’t have an oscilloscope?
Swagatam says
you can the check average DC voltage on the output pins of SG3525 while adjusting the pwm until it is almost 50% of the supply voltage, this will hopefully fix the most favorable modified waveform for your circuit…make sure your transformer also is rated at this 50% less rating at the primary side.
Abbey says
good day sir. thanks for all your post. Pls is the first circuit square wave or modified sine wave? if the last design uses sg3525 and it is square, what make the first circuit to be modify sine wave. is sg355A the same to sg3525?
Swagatam says
adjust the PWM pot appropriately to make it a modified sinewave.
Abbey says
well done sir. Pls is the output from design1 modify sine wave or square wave. I am somehow confuse. since the last design using SG325 is said to be square wave I think the first design also suppose to be square. what make the difference. is SG3525A the same with SG535. thanks.
Swagatam says
Thanks Abbey, for a modified version you must have the PWMs adjusted such that each block is followed by a gap or a “dead time” meaning it should be one square block then a “null” then the next square block and again another null and so on. This waveform when dumped into transformer winding will try to implement a sine wave like waveform.
In any SG3525 when you adjust the PWM feature to do the above then it becomes a modified sinewave. So it just depends how you are adjusting this PWM structure through the given pot.
If this pot is adjusted to produce full square waves then it is no longer a modified sinewave rather a simple square wave.
Chinomso says
Hello sir, I actually built the above inverter circuit using ic sg3524 and 555 timer as the sine wave generator. I feed the 555 timer stage with 5v beside 8v fed to the ic sg3524. However, the pwm from ic sg3524 is being blocked by the collectors of the bc547 transistors at the bases of the power stage transistors. The question must sg3524 and 555 timer ICs have the same voltage feed or could there be something else?
Swagatam says
Chinomso, the lower two BC547 are wired to chop the mosfet gate 50Hz pulses into smaller sections as per the PWM rate, …..it won’t block anything.
IC 555 can work comfortably with all voltages between 5V and 15V, so no problem with 5V…still you can use 8V for the IC 555 also to clear all doubts
Love says
Hi Swag, I have question on the 2 pure sine inverters I made. First, a 2kva/24v with trafo using 12swg in the primary side and 18swg on secondary with adequate filter capacitor 5uf, it carries my freezer easily even at 5% battery level
However, I made a 3.5kva/36v with trafo using 12.5 swg primary and 16swg secondary even with 32uf filter capacitor it could not carry same freezer at 40% battery level but carries it at 75% or more battery level.
Sir,what could be responsibl for this low power bigger trafo pure sine inverter(according to your design)that could not carry much load. Thanks Chief.
Swagatam says
Love, did you calculate the parameters perfectly while designing the transformers? If you do it by trial and error then that won’t allow you to understand anything regarding its working principle. By the way 12 and 18 SWG ratio does not look OK, neither does does 12.5 and 16 SWG ratio. The secondary side should have proportionately much thinner wire than the primary side.
Please do it with proper calculation and if possible take the help of a professional transformer designer.
Love says
Hi Swagtagam, please what is the effect of using high value filter like 32uf in this inverter
Swagatam says
Hi Love, if you are referring to the transformer output capacitor, 32uF would waste a significant amount of power, not recommended.
Love says
Thank you for the update, please for 10kva/120v input, what are the modifications.
Swagatam says
upgrade mosfet and transformer rating accordingly.
Love says
How can I step down the voltage input into the oscillator, and for 120v input which MOSFET can I use. Will irfp 260 do
Swagatam says
you can use 7812 IC for stepping down…..please check the datasheet of the mosfet and make sure the Vds and Id specs are as per the required specs.
Love says
Please how can I add a power saving mode to this design to conserve energy. Thanks so much Swag.
Swagatam says
You can add this to your inverter:
https://www.homemade-circuits.com/2015/07/no-load-detector-and-cut-off-circuit.html
Ekoe Anthony says
Hello enginner , Secondly we all understand that technologies have reached its peak, such that it is like morden inovations principles are trying to disagree with early lay down principles upon which many have built their knowledge. Please my questions. I have seen from a blogger from Indonensia who display a pure sine power inverter with frequencies, one is after building gives 77hz ,second 32 hz.Which from his videos he used induction machines like electric driller, fridge,water pump,set up table computer and eletric stove. I am not quiet at ease with it. I know please globally two grid frequencies 50 & 60hzs please your advice.
Swagatam says
Ekoe, the frequency of a pwm based inverter must be measured and confirmed using an oscilloscope, a multi-meter can give misleading results.
Joseph says
Please swag.I need a pure sine wave inverter circuit that uses two ir2110 for high/low drive to the transformer.It may use any oscillator.
Swagatam says
Hi Joseph, you can refer to the second circuit on this link:
https://www.homemade-circuits.com/simplest-full-bridge-inverter-circuit/
Swagatam says
For sine wave you have to integrate SPWM at the low side MOSFETs
Ekoe Anthony says
Hi Swagatam, I want you once again that you trow more light on the concepts of choosing transformer and power transistor to a paticulation power inverter oscilation circuit to obtain a desired power. Please consider me, am still not getting hold on this fundamental principles.
Swagatam says
Hi Ekoe, there’s nothing complicated in it, just divide the maximum intended load wattage with the battery voltage and get the amp value, then make sure the transformer’s and mosfet’s V and I rating are higher than these acquired value
tinuke says
Hi sir, I use copper wire for my MOSFET cascade but when the MOSFETs got burnt due to any reason, and I replace the MOSFETs with same quoted Copper with the black soot from the burnt MOSFETs , the MOSFETs blow again until I change the copper wire. Then no more MOSFETs burning and the inverter is working fine.
Swagatam says
OK, thanks for updating the issue!
tinuke says
Hi sir, sorry I was trying to ask why the MOSFET blowing incident. Thanks
Swagatam says
Tinuke, mosfets are complex devices, and there can be many reasons for their malfunctioning, you can read the details here
https://www.homemade-circuits.com/mosfet-protection-basics-explained-is/
tinuke says
Thanks Sir, please why is my built inverter gets voltage stable at 220v, 61hz, what could be factors for the 61hz frequency and how can I make it 50hz.
Swagatam says
Hi Tinuke, please measure the frequency across the output pins of the IC, do this by disconnecting the mosfets from the IC, confirm whether it is 50Hz or not….
tinuke says
I checked, it was 61hz but when the frequency pot was adjusted it got to 50hz.
Swagatam says
then keep the pot adjusted to 50Hz and check again
tinuke says
Thanks it is better after several tweaking I now got 52hz, please what is the size of Ac output capacitor can I use for 5kva/48v because the combination you gave from the redirected page, is not efficient.
Swagatam says
I am glad you could get the right frequency tinuke, however I am sorry, I do not have any other calculations other than what I suggested you in the referred page.
tinuke says
Well done Swagtagam, please how can I set the spwm or pwm (comparing circuits ) preset correctly to get pure sine wave without an oscilloscope because I turned the preset to Max and min without obvious difference.
Swagatam says
Tinuke, there’s no way to confirm a sine waveform without using an oscilloscope, but to some extent it can be verified through a multimeter by checking the output of the transformer. If the voltage varies in response to PWM variations that would confirm that the PWM function is working.
tinuke says
Thanks, I checked the spwm output, it varies as I turned the preset, does that mean it is working.
Swagatam says
The 220V output from the transformer must change in response to the PWM variation.
tinuke says
Thanks sir, the trafo output is changing with pwm variation, please how can i avoid spurious sine wave.
Swagatam says
sorry I could not understand what you mean by “spurious sinewave”
tinuke says
Thanks for your response, I have sorted out the wave. It’s working great. Between modified and pure sine wave I made using your circuits, the two inverters carried the freezer, but the pure sine worked smoother but the two required thesame output filter.
I thought pure wave inverter will require lesser filtering to carry the freezer. Please educate me
Swagatam says
Great, I am glad you could sort it out, the filter capacitor or inductor values can be experimented manually…. but only with the help of a oscilloscope
tinuke says
Hello sir, I checked the waveform using goldwave software for the waveform looked the same for the three-modified inverter, pure sine wave inverter I built at 50hz and the public utility power supply. They all produced sine wave. But at extreme of the preset value for pwm of pure inverter and at 51hz upward for the modified inverter, the waveform was poor.
I want to ask why did the modified inverter produced same good sine wave as the pure inverter and the utility. Thanks for your enlightenment.
Swagatam says
Tinuke, the Goldwave software is actually designed for analyzing music frequencies, I am not sure whether it will be able to check an inverter frequency, because when I tried to check square wave from an inverter using this software it simply did not work.
Can you please specify which two inverter designs are you comparing? Is it from this website??
tinuke says
A sg3524 circuit but upgraded it to the pure sine wave using your pwm bjt stage.any suggestion please
Swagatam says
OK, but you will have to use a real oscilloscope to test the waveform, a PC based software might not give correct results. You can try the following concepts for making an osciloscope at home for the purpose
https://www.homemade-circuits.com/?s=oscilloscope
tinuke says
Thanks Swag, i got an oscilloscope, the waveforms are different for the utility, pure and modified sine inverter. I tried tweaking the filter output and the pwm preset but the pure sine inverter I made using your bjt/ pwm stage didn’t come out as perfect as the utility power supply. Although the waveform was better than the modified inverter. Please how can I improve this. Thanks.
Swagatam says
Hi Tinuke, what kind of SPWM are you seeing in the oscilloscope? How many blocks are there on each waveform and in what order? Please clarify these I may try to help!
tinuke says
There are combination of sine and sawtooth waveform( occasionally), 2 blocks in a waveform. There are different waveform with different load. Thanks so much sir.
Swagatam says
Please check on the DC side, and make sure the blocks are in the SPWM format, that is widest block at the center and gradually narrowing blocks on either sides.
Total number of blocks should not be more than 7
tinuke says
Thanks Swag, there are four blocks with the second, the widest. Any advice please.
Swagatam says
Tinuke, it number of blocks should an odd number, like 3, 5 or 7, and the widest block should be at the center, so please make sure the SPWM is configured correctly.
tinuke says
It is three blocks, the widest block the first. Thanks for the correction.
Swagatam says
the widest block should be at the center! and preferably there should be 5 blocks as shown in the IC 741 output in the above article
tinuke says
Please how can I make it 5 blocks, any modifications sir
Swagatam says
the fast triangle waves must be 5 times more than the slow triangle waves.
tinuke says
Good day sir, from the spectrograph of this pure sine inverter I built, there are so many harmonics as compared with the bought pure sine inverter an the utility supply, please how can I reduce the harmonics, I have used different filters. Thanks Swagtagam.
Swagatam says
Hi Tinuke, Can you show me the image of the spectrograph? I’ll try to analyze the reason. Upload it to any free image hosting site, and provide the link here.
Swagatam says
By the way you must use an oscilloscope for analyzing the waveform, i am not sure how a spectrograph can work for analyzing inverter waveform.
Ola says
Good day swag, Can this circuit be modify to single transformer inverter, what are the components in modification? thanks
Swagatam says
yes it can be perhaps done, by modifying the transformer, mosfet stages in the same way as implemented in one of the relevant designs in this website.
Glory says
I made this circuits working perfectly 1.5kva/24v, with LC filter but when I load my washing machine at few times the output frequency which was set at 50hz jumped to 2.2khz,16khz…. For 1second To return to 50hz, why this, what can I do, I added more filters no difference. Thanks
Swagatam says
I am glad you could make it successfully, however the issue which you have mentioned can be difficult diagnose without a practical check, it could be perhaps happening due to instantaneous harmonics generated by the transformer winding or by the load motor winding…you can try installing MOVs at different nodes of the circuit and check if that solves the issue
Glory says
Yet to get resolved, any other advice Sir.
Glory says
Which filter system is good for inverter output. RC or LC system
Swagatam says
LC is more effective as far as I know…
abioye says
and sir can i use bc546/ bc547 because i could not find bc556/bc557 thanks
Swagatam says
one should be NPN and the other PNP….BC546 is not a PNP, so please make sure to replace it with a pnp
by the way the shown pair is not BC556/BC547…rather they are BC547/BC557…
abioye says
sir can pin 4 of sg3525 generate slow triangular wave form as you mentioned in one of your post
Swagatam says
the Ct pin (pin#5) is supposed to generate it…please confirm it with a scope first
abioye says
thanks sir for your quick reply
one more thing sir to creat the SPWM device that mean instead of using two ic556 to creat slow and fast triangular wave form i can just make use of only one ic555 and ic741 while i tap a slow trianguler wave form from the sg3525 to generate SPWM for the inverter
Swagatam says
yes that’s possible, but just check and confirm whether the triangle wave from the SG3525 has a peak equal to the 555 triangle peak or not…they should be approximately equal for optimal results
abioye says
sir i was reading through some of your comment to ( mr faith) of how to generate SPWM under this thread you said that one can extract triangular wave form from pin 4 of sg3525 for slow triangular wave form
and pin 6 and 2 of any ic 555 wired as a astable circiut for fast triangular wave form
sir my question is that the diagram of ic555 being provided by you sir has a resistor port for adjusting the PWM output
sir my guess is that as we adjust the port we increase or decrease the voltage at the transformer output or will we have to modified the ic555 circuit
my last question is sir are we going to make use of the PWM being generated by the ic555 thanks sir
Swagatam says
Abioye,
As per my assumptions, adjusting the PWM to extreme levels may cause abnormal SPWM behavior, because too narrow or too wide PWMs may force the triangle waves to become discontinuous or without significant valleys between the triangle waves which can cause inefficient SPWMs. But yes it can be applied for controlling the output RMS voltage of the inveter. The ideal PWM should be to a 50% ON/OFF cycle for initiating a reasonably uniform triangle waves…all these will to be verified with practical trial and error method…
Tolu says
Please, how can I make the inverter frequency stable at 50hz as against 55hz I presently get. I desire it to be 50z. Thanks
Swagatam says
use a voltage regulator for the IC, such as a 7812 IC
Tolu says
Thanks sir, I put 7812. But still 55hz. Is it possible for a pure sine wave inverter to have a frequency of 55hz
Swagatam says
measure it across the IC output pins with a good frequency meter….alternatively you can feed the IC SG3525 externally using a separate oscillator IC circuit such as IC 555
Swagatam says
55Hz may not be appropriate for any appliances
Tolu says
Please any circuit for the combination of sg3525 and 555 for better frequency output.
Tolu says
Hello, my inverter is faulty affect some months of usage, I discovered two bjt transistor were bad, why sudden damage, although the output to drive the MOSFETs is a bit different, 7.02v and 6.90v could this be a reason
Swagatam says
which schematic are you referring you to?
Tolu says
The bjt/pwm stage in this page, the bc547/bc557
Swagatam says
keep the fast frequency of the SPWM to 350Hz, not more than this. try adding a 1K resistor across gate/source of each mosfet
Dayo says
Hi swagatam , my friend bought a standard purewave inverter, but about 6months the crt TV got burnt why the led TV is still working. I found the parameters are still 228v output voltage, frequency 50.12hz, what could make the TV got burnt.
Swagatam says
Dayo, LED/LCD TVs normally incorporate a stabilized SMPS for powering the circuitry…therefore these are well protected internally and can survive upto 300V, and that may be reason why the LED TV is not yet affected, while the CRT which was not so well equipped burned due to a possible switch ON surge…
Dayo says
Good day sir, I built this inverter, but within hours of use with my CRT TV, the TV color behaves funny in that the pictures go so dark that I barely see the image then later come out so nice. Please what could be wrong sir, help out. Thanks
Swagatam says
Dayo, that could be due to a loose connection, a bad solder, or a low battery…..please use a good PCB for making the inverter circuit and check the response again…also make sure the output from the inverter is below 250V
Dayo says
Please how does low battery affect it, because my battery is presently bad. Thanks.
Swagatam says
CRT TVs will generally blackout under low voltage conditions, below 170V. Try an LCD or LED TV, they will work without problems, until ofcourse the voltage drops too low!
Dayo says
OK sir, my TV input voltage is 110-240v, please could there be any other reason.
Dayo says
OK sir, but the old modified sine inverter I used for years didn’t have this issue but I wanted to try to upgrade to pure sine wave using a 555 ic and an opamp ic with your bjt stage.
Even now when I uae the modified inverter it now have the same issue. Please help .
Swagatam says
It will be difficult to understand because I don’t know anything about the modified inverter circuit and its specification. The best thing would be to monitor the waveform and voltage during the testing period…
Faith says
I know how to generate my spwm what am asking is that i will be needing a second opamp for my feedback and again
Please can you give a range which the frequency of the filter will fall or can it be the same frequency as the spwm
Swagatam says
sorry, I have no idea regarding the filter frequency…you will have to calculate it with thorough experimentation.
Faith says
Ok that is i will be needing a second opamp, and again Please can you give a range which the frequency will fall or can it be the same frequency as the spwm. Lastly can i use the circuit for hbridge
Swagatam says
for the triangle slow wave you can extract it by processing the output from pin#4 of SG3525.
the fast triangle waves can be achieved from pin#6/2 of any standard IC 555 astable circuit
you can use the SPWM circuit for H-bridge also
faith says
Good day Mr swag., i want to thank you first for your good work, but i have few question to ask
1. If i use spwm to modulate the signal i.e instead of using pwm i now use spwm how do i set my feedback considering that i will generate my spwm using two 555timer and one comparator.
2. What will be the frequency of my output filter is it a high frequency filter or a low frequency filter
Swagatam says
feedback can be achieved through an opamp comparator stage by configuring it with a resistive divider stage across the inverter output, and the output of the opamp fed to pin#1 of IC 3525. The resistive network should be adjusted such that whenever the output tends to go higher than the normal level, the oamp output turns high narrowing the PWM content
the output should have a high frequency cut off filter
Ekoe Anthony says
Good day My Tutor,
Is it possible to use a none centre tap transformer in any inverter circuit using already a center tap transformer? If real , what modification can be done?
Swagatam says
Ekoe, that can be possible only if the oscillator section replaced with a full bridge IC stage, please type full bridge in the search box, you will be able to find a few concepts using this topology.
Ekoe Anthony says
Hello Swag, When you are building any Power inverter circuit , and you want to match with a transformer to obtain a maximum loading power for example a center tap, is it the voltage that you have from the output A& B of the circuit as a driver voltage let’s say from 3-9volts to the power transistors , on that you base your transformer input voltage say 7 -12volts?
Swagatam says
You have to consider the average voltage which is coming to the gate or base of the power devices from the IC, and then make sure that the current of the trafo is selected as per the load wattage with respect to this voltage, that is if the required load wattage is 200 watt, and the average voltage from the IC to the mosfet gate is 6V, then the trafo must be rated at 6-0-6V and 200/6 = 33 amps for primary…and for secondary this will be proportionately = 200/220 = 0.9 amps.
Ekoe Anthony says
Hello Engineer,
Please educate me on this very issues and ease my mind. My question is odd, and is this, Any time I am browsing through the internet and I see any educative article either in video or not, films and music. You will always see subscribe, now if I go ahead dowloadind Am I doing harm in cheating on the publisher of these articles? Or the money deducted from my internet bundle after is shared indirectly to the owner of the website. Please what is the right procedure, endure with me thanks .Because I want to correct my mistakes.
Swagatam says
Hello Ekoe, subscribing and downloading is not wrong for the publisher, but frequent downloading will increase your internet bill for sure
Lm324n says
I made sg3525 inverter but one ouput of sg3525 is higher than the other output about 1 volt
Is my ic fualty
Swagatam says
1V difference may not be a problem, but is it oscillating? confirm this with a frequency meter or with a headphone…
thatcher says
How to check oscillations with headphones?
Swagatam says
connect the headphone leads with the output of the IC, vary the frequency pot of the IC, and tweak it until you find an audible note on the headphone…this will confirm that the IC is oscillating and is working OK
Lm324n says
Can i use sg3524 instead of sg3525
Swagatam says
yes you can
Ekoe Anthony says
Thanks Mr Swagatam for the quick response to my question on my modified inverter more grease to your elbows.
Swagatam says
You are welcome!
Ekoe Anthony says
Hello Mr Swagatam happy new year,
My tutor, am building a modified inverter with sg3524 circuit. I used 1400VA transformer from an old UPS, When I put power into the inverter the battery negative terminal get what quickly within 1 minute as if the cross section of the cable is small. Also the power transistors run very hot which cannot last for an hour .The primary input of the transformer reads 9volts a center tap, and it sounds heavily when powered. Am confused engineer, resolve my problem please thanks.
Swagatam says
Happy New Year to you Ekoe,
This can happen either due to a mismatch between between battery voltage and the transformer voltage rating, an unbalanced trafo winding or a faulty IC which may be generating incorrect oscillations or frequency. please check all this parameters using an oscilloscope or other suitable test equipment and make sure these are perfectly implemented
francis says
Many thanks to you. Sir I have a problem on the buffer stage, am getting 4-5 volts on mosfets gates instead of 12v why? I have changed all the transistor still the same, I also tried other transistors(c1815 and a673) on another pcb no change. But when I isolated base of the bc557s the voltages rose to nearly12v. Where am I lost?
Swagatam says
50% less reading is fine, and is due to 50% duty cycle of the SG3525 oscillator wich is causing the meter to simulate the average 50% value of the supply level, you can confirm the same on the output pins of the iC directly…if the readings match then you can assume this to be perfectly normal.
removing 557 removes the negative cycles from the reading, causing the meter to show only the ON time, so may be this is causing the 12V to appear on the meter
francis says
Thanks once again for that. If that is normal as you said then will that be good enough to drive 20NM50 on h-bridge without causing them to overheat?
Swagatam says
What you are seeing on the meter is the average value of the voltage but the peak value is always 12V (or the supply level), meaning the ON time of the frequency is always producing 12V, therefore any connected mosfets will have no problems conducting optimally
francis says
Thanks once again. I have introduced the 555 circuit to my inverter but now the lower two bc547s are shorting the oscillations completed ie from 5.6v down to 0v. I measured the output of 555 is 11.5v but I not sure if that is PWM because I don’t have oscilloscope.
I tried to built another circuit using other components of same marks but still.
Swagatam says
your PWM IC 555’s output at pin#3 should vary from 5% to 95% of the supply voltage that’s applied at pin#4/8 of this IC in response to the PWM pot rotations.
If this is not happening then your PWM circuit might not be working or could be having some fault…please confirm this…
francis says
Ok I see so what is the best position of potentiometer to achieve a fair waveform I have set it at the middle inverter working fine but I don’t know how the waveform is like because I don’t have the oscilloscope?
Swagatam says
the waveform will be quiet similar to what is shown in the following article
https://www.homemade-circuits.com/modified-sine-wave-inverter-circuit-2/
set the PWM which allows the gate voltage of the mosfet to be at a level equal to the transformers winding rating…if the winding is 6-0-6, then make sure it is 6V, or if the trafo rating is 7.5–07.5 then adjust it to 7.5V approx these would be with reference to a 12V battery.
francis says
hello sir
i salute the great job you are doing, where else can we find free tutorials like these?
i think you have been sent by the heavens……
i constructed the above circuit which was drawn by Ainsworth Lynch, the 3525 did not output signal from pin 11 and 14 though it was warm meaning there was power. i looked again into the schematic and compared to the one you drew and found that pin 9 was directly connected to the ground instead to the R1 which then link pin1. after that correction there was output.
although i am a new born to electronics ,I’m a hobbyist of electronics wiling to know better.
My question is ……. whats the prpose of 555 and lower two transistors ,can that not short pulses from 3525 to ground?
Swagatam says
Hello Francis,
I am glad you liked my site.
Yes it seems the drawing created by Ainsworth has a mistake, no problem readers can correct it by following the other diagram, and anyway this article is not about the SG3525 circuit, it’s primarily regarding understanding the technique of converting any square wave inverter into a sinewave.
The IC 555 or the SWPM feed will short the waveform, but it will do it in steps which will ultimately take the shape of a sinewave at the output of the inverter therefore chopping or shorting of the actual square waveform into stepped waveform is deliberately introduced in order to acquire the intended sinewave output.
If you have any further questions regarding any of the concepts presented in this website, you can feel free to inquire, and get them solved from me.
francis says
Ok I now understand the use of 555 in that circuit.one more question, how is the pwm from 555 ic incorperated to short part of the waveform at the right time to reshape square wave into stepped waveform? Is it because the two ic start at the same time or ? What if I introduce the the pwm from 555 later in the operation of 3525 ? In other word how does the two ic sync?
Swagatam says
The bottom concept does not require synchronization because it is not generating an SPWM, it is only chopping the square wave into uniform pieces therefore it does not have to be in sync with anything, however if an SPWM is employed where the each waveform needs to be carved with precise sets of PWMs then syncing may be required.
You can see how the procedure is implemented in the following example
https://www.homemade-circuits.com/5kva-transformerless-inverter-circuit/
denmark says
sir swag…can you give me the part list of this pure sine wave inverter using sg3525 because other component is not clear…plss sir…
Swagatam says
Hi Denmark,
please do one thing, just copy down all the part numbers that you are able to see in the circuit diagram, and send it here, I’ll check it and verify it for you…. and if required add more info in it.
Dayo says
Good day sir, please what can I do to frequency drift of my inverter in response to variation to battery level and load. Thanks
Swagatam says
operate the oscillator stage through a 7805 or 7809 IC regulator…
Dayo says
I used 7812, is it bad . Thanks
Swagatam says
is it controlling the supply to the IC at 12V constant, throughout??
Dayo says
Yes, the supply is constant.
Swagatam says
with constant supply, frequency cannot vary for any IC, better check the voltage or the frequency again carefully
Dayo says
I used 100uf capacitor with 7812 regulator, it supplies constant voltage initially but as battery level changes the frequency drifts
Swagatam says
try 7809 IC
Dayo says
Sir, I have 7805, can I use it.
Solomon says
How can i set the frequency of the circuit, or to calculate it?
Swagatam says
please check its datasheet for all the details..
Solomon says
Pls sir i need your help, so now fo this present circuit what is the frequency?
Swagatam says
Solomon, frequency should be set to 50Hz, and you can check this across the output pins of the SG3525 using a frequency meter
Solomon says
Hello swagatam, thank u very much for helping alot in construction of this wonder inverter circuit, what i need now is to help me design a pwm generator circuit using op amp for pure sine wave output. Thanks
Swagatam says
You are welcome solomon, the PWM generator is already explained in the article….if you want to replace the IC 556 with opamp then you will have to use a opamp based triangle wave generator such as this one
https://www.homemade-circuits.com/wp-content/uploads/2017/12/opamp-integrator.png
you will need two of these, with different frequency setting to get the required fast and slow triangle waves.
The square wave input can be fed from a IC 555 circuit.
Solomon says
Thanks. Sir, is there need for delay timer for an inverter?
Swagatam says
that depends on the user preference, it is not necessary.
Solomon says
Hello sir, i have to questions to ask:
1. what is the minimum AH battery can each of the inverter can handle: 5000w, 2000w, 1000w?
2. What is the maximum current for charging each of the battery: 100AH, 50AH, 12AH?
Swagatam says
Hello Solomon,
the circuit can handle any battery with any rating as desired by the user.
The mosfets and the trafo ratings will need to be matched with the battery rating appropriately.
It is ideally 1/10th of the AH rating, divide the AH with 10…..
Solomon says
Thank u sir, But is any problem if i connect the four MOSFETS together on 500w transformer and use 50AH Battery?
Swagatam says
If two mosfets can handle the power then adding extra two will be a waste, it’s your wish, you can add them if you want.
You can use a 50 AH battery for a 500w trafo , there are no restrictions as such…
Solomon says
Thank u very much sir. Pls more questions sir. I raised an argument with my friend about N channel power MOSFETs, there are some of the MOSFETs that has a diode symbol on their body, he said that those that have the diode symbol on them are local quality product and get hot easily or even burst during operation while those that doesnt have the symbol are good and original quality, and i oppose that. Pls help me with the correct answer.
Second question: in the second circuit containing SG3525 Ic, which type of capacitor can i use for the non polarized, is it ceramic or polypropylen type or both. help me and clear my doubt. Thanks
Swagatam says
Hi Solomon, your friend is wrong, and he doesn’t make sense. All modern mosfets today have an internal diode for back EMF protection, and it is an enhanced property designed within all modern mosfets.
For the capacitors you can use any good quality 50V rated non-polar capacitors, even ceramic discs will work as fine….
Solomon says
Well done sir, i salute you. Thanks alot, one more question: what will be my waveform output if i use 555 timer for pwm
Swagatam says
You are welcome Solomon, the output waveform will be just as shown in the following article
https://www.homemade-circuits.com/modified-sine-wave-inverter-circuit-2/
Solomon says
Thanks, Sir, if i use Four MOSFETs(two-two each side of the winding) can it handle 5kva transformer? Because i want to use IRF1404, which power of transformer can it handle 1000w, 2000w
Swagatam says
Yes definitely it will be able to take 5kva, but make sure to mount them on large heatsinks…
if the power output is 5kva then naturally the trafo has to be a 5kva or around 5000 watts
Solomon says
sir pls dnt be tired with me, i wanted to gather all my questions to post, but i forgot, before i still forget, i have more questions:
1. in choosing or selecting the MOSFETs, what must i consider, is it the volt or the amp?
2. For knowing sake, i there any diferences or similarities between an inverter transformer and a stabiler.
transformer in terms of winding?
3. Can i use a stabiler transfor(5kva stabilizer transformer) to connect my inverter circuit with?
4. What is the relationship between MOSFETs and transformer in terms of power capacity. Pls help, thanks.
Swagatam says
Hi solomon, here are the answers:
1) you must primarily check the Drain-Source voltage and the continuous Drain current ratings for mosfets
2) All transformers work with the same principles so there’s no difference as far as functioning is concerned, only the V and I ratings may be different…
3) You can if the winding specs are compatible…
4) mosfets are just switches, therefore their current and voltage rating must be adequately rated to handle the trafo wattage…preferably the rating of the mosfet should be at least 1.5 times higher than the trafo max wattage.
Solomon says
Hello sir, thanks for the circuit, i appreciate and so grateful. I have something to ask whether it can work, can i configure those MOSFETS in pairs? (meaning each side two-two)
Swagatam says
Thanks Solomon, yes definitely you can add more mosfets in parallel for upgrading the capacity of the design….
Solomon says
Ok, thank u sir. Sir, when connecting them parallel must i connect a resistors in series with their or just direct parallel connection, if with resistor what values
Swagatam says
yes all the mosfets must have their own gate resistors, any value between 10 and 100 ohm will work
Tolu says
Good day sir, I made a 36v inverter but I have issues with the duty cycle, without load is 60% but with load 50%. I have tried LC filter but no avail, please assist.
Swagatam says
Tolu, duty cycle should be 50%, so it is not an issue…you must check the voltage at the output…..
Tolu says
Good day sir, voltage is varied from 190-250v but still between 58-60%
Tolu says
Duty cycle is between 58-60%
Swagatam says
how are you measuring the duty cycle??
Tolu says
I use my multimeter
Swagatam says
how can you check duty cycle with multimeter?? how will you know what is the exact ON time and OFF time through a DMM??
chucks says
hello sir.. thanks for updating our ideas on electronic.. please sir I need an Automatic change over circuit that will automatically switch over my inverter to power source in my room when light is been restore.. thanks
Swagatam says
chucks, such designs are already present in my website, please check the relay changeover category
kels says
thank you for your good works!, can I use it for my sg3524 circuit
Swagatam says
thanks, yes you can use it…
Solomon says
Hello sir, pls i have few questions to ask:
1. I want to add power transistors (2N3055) to this circuit when completed with the SG3525 circuit, and i want to use the arrengement and the pin connection like the circuit of 200VA square wave inverter u posted, i want to increase the wattage of the circuit using the transistor, pls help me to configure the pin connections where to connect them.
2. Can i use the AC mains output of the inverter circuit to a 12v battery charger to charge the battery of the inverter itself? Is there any effect to the battery or to the inverter? Pls help me sir. Thanks
Swagatam says
solomon,
you can replicate the arrangement which is shown in the following design, and use it directly with SG3525 circuit
https://www.homemade-circuits.com/48-v-inverter-circuit/
your second point cannot be feasible…
solomon says
ok, thank u sir, so now what will be the maximum power of the circuit
Swagatam says
Maximum power will solely depend on the wattage of the trafo and the battery AH rating…
Love says
Thanks sir, I made a pure sine wave inverter 1Kva , buy goes off after 40mins which I will need to switch on again, mosfets are cool. I troubleshoot , couldn’t get the fault. Please, what can I do . Well done sir.
Swagatam says
Love, which circuit did you make? without seeing the schematic or the block diagram it can be difficult for me to judge the fault??
denmark says
sir can you suggest what is best in our thesis project….we want to build a power inverter for our school…in case of power outtage we have emergency electricity…we want to installed it in our electronics lab…plsss sir…we need a tested power inverter that can run the appliance at the same time …tnx sir…
Swagatam says
Hi Denmark,
All inverter circuits are tested designs here, either by me or by the users, but all these circuits require an expert level knowledge to complete them successfully.
I can suggest you a simple one which you an try, here’s the link:
https://www.homemade-circuits.com/how-to-make-simple-200-va-homemade/
Dayo says
Please sir, if I want to do 48v inverter, will I feed 48v +dc battery in bjt stage or will I step down to 12v to feed into it. Thanks
Swagatam says
Dayo, only the trafo center tap will connect with 48V source, rest everything must be isolated and connected with a 12V or 15V input
denmark says
Sir good day, what is the value of transformer…
Swagatam says
you can choose any value as per your required specifications and battery specifications
denmark says
Sir can i ask if these project is tested…and can you give me the parts list of this project….sir i am a electronics student turning 4th year college and our thesis project is power inverter using dual motor…can you suggest sir if what inverter is the best for our project….that can run the appliance and bulb in case of power outtage or brown out in our school..we want to installed it in our electronics lab.. Thank you very much sir…godbless you
Solomon says
Hello sir, pls i have some question that u should help me answer in the first circuit:
1. What output waveform, it is modified sine wave or pure sine wave?
2. what is the function of the two MOSFETs at the 12v tap of the transformer
3. What does it mean by the resistor 10E
4. How can i attach/connect the pins of a power transistors(2n3055) to the circuit. Pls sir help me to answer them
Swagatam says
Ansrwes:
1) If you use SPWM feed it will be pure sinewave.
2) the mosfets respond to the gate frequency and correspondingly switch the two transformer winding with high current. alternately.
3) 10E = 10 Ohm
4)You can connect them as indicated in the following article, using a Darlington pair:
https://www.homemade-circuits.com/48-v-inverter-circuit/
Solomon says
Thank u very much sir, in fact i appreciate, one more question pls, what is the function of the capacitor at the output transformer?
Swagatam says
The capacitor is to smoothen the output waveform and make it more like a sinewave output
Solomon says
Sir, For the MOSFETs, can i use IRF540? or pls tell me a recommended MOSFET atleast two or three different types
Swagatam says
yes IRF540 will work!
Solomon says
Hello sir, where is pwm output for this circuit
Swagatam says
PWM is obtained from the IC 555 circuit or the opamp SPWM circuit.
Ekoe Anthony says
Hello Mr Swaggart, Can a choice of a timing capacitor and resistance when calibrating an I.C for frequency let’s say 50hz.Would it influence the d.c & ac current or voltage at the outputs of the I.c circuit. Is it a factor? Please Doc.
Swagatam says
Hello Ekoe, do you mean to say the duty cycle?? yes the duty cycle or the ON/OFF time of the 50Hz frequency can affect the output current and voltage….it should be set at 50% duty cycle to ensure a 100% current/voltage output
Dayo says
When I measured the the frequency was not stable ranging from 120hz-260hz. Can it still work
Swagatam says
where did you measure the frequency? please provide proper details
Dayo says
When I measured the down the frequency was not stable ranging from 120hz-260hz. Can it still work
Swagatam says
what is down frequency?
Dayo says
Hello, is possible to measure the frequency of spwm and set before connecting to be bjt stage.
Swagatam says
yes, and that has to be done without fail…
Dayo says
Hello, I made two inverters one works at 150hz but the mosfet did not blow with an inductive load but blow at 50hz for the second inverter. Why, and what can I do
Swagatam says
that will be difficult to judge, because mosfets can blow due a many different reasons, mostly due to parasitic inductance within the tracks, volatge spikes etc…
https://www.homemade-circuits.com/mosfet-protection-basics-explained-is/
tinuke says
Good day engineer, I made a 36v inverter(secondary trafo guage is 16swg)
but when used to power washing machine, the machine works heavily but when used with 12v inverter, the machine works smoothly.
Swagatam says
Tinuke, it’s simply beause your 36W inverter is not correctly built and it is not delivering the required amount of current to the load….you can confirm by attaching an ammeter in series with the battery and check how much current it draws, and then multiply the result with the battery voltage…that will give you the output power range of the inverter
Swagatam says
if you think everything is correct then where is the fault?? something has to be wrong somewhere…which you must find out
you cannot troubleshoot or build a circuit without understanding the stages or without proper equipment.
please do not make it blindly, check the stages with a meter with proper understanding, if your BC547 is ON continuously it means your 741 IC is not producing the PWMs.
Swagatam says
you can use 3.3V also
Swagatam says
did you understand why the zener is being used, no point in trying randomly…
Swagatam says
yes it will do…
tinuke says
Please help me design a circuit for inverter voltage stabilization in reference to varying battery voltage and load variation. Thanks sir
Swagatam says
I think I have already referred you the circuit in one of the previous comments, anyway you can check it out here
https://www.homemade-circuits.com/automatic-output-voltage-regulator/
the output will be regulated only as long as it is not an overloaded
Swagatam says
Try adding a 4.7V zener diode at the output of the IC 741…may be the IC 741 is generating a leakage voltage which is causing permanent switch ON of the BC547
Swagatam says
you must check waveform for this circuit, checking volts will not help…
please don’t do it unless you have without proper equipment and detailed understanding.
Swagatam says
how would you check the output waveform and whether it is generating PWM or not?, please tell me how will you confirm this without a scope???
tinuke says
Hello sir, please between mosfet and igbt which one is better in efficiency and other features assuming they have same spec
Swagatam says
It is IGBT which has better efficiency than mosfet, if the load current requirement is high
Ekoe Anthony says
Hello engineer, what would happen if any power inverter built with 60hz frequency is used for electrical gadgets operating on 50hz frequency.
And if there would not be any trouble can this application be done the other way round ?
Swagatam says
Hello Ekoe, except inductive loads or timer based loads, it wouldn’t have much effects on the load
TILIN OOMMEN says
hi
iam building an 1KVA inverter using isw20n90 mosfets. but i needed a closed loop pwm driver ic for my inverter
can you suggest me any IC which i can get it in market.
Swagatam says
Hi, by closed loop do you mean an automatic load control through feedback? Please elaborate on this
Abhilash Sharma S says
Sorry the frequecy of switching is 20 KHz
Abhilash Sharma S says
Hi Sir,
I am designing a Bi directional Inverter for domestic application having a variable load, I should drive mosfets using a spwm IC which can support a closed loop purpose,
The output load limit is 600 W, the mosfet used are isw20n90, the switching frequency shall be greater than 200kHz, can you please suggest me an IC for this purpose
Thanks in advance
Swagatam says
Hi Abhilash, by bidirectional do you mean to say a full bridge type?
Anyway, you can refer to the following design, which will perhaps fulfill your need:
https://www.homemade-circuits.com/5kva-transformerless-inverter-circuit/
Reoc says
Hi Swag,
I want to know if adding a pull-down resistor between the outputs of SG3525 (before connecting the gate resistor) will help the switching performance of the IC.
Swagatam says
Hi Reoc, it is not mentioned anywhere in the datasheet of the IC, still there’s no harm in trying it.
tinuke says
Hello sir, please how can I minimize my modified wave inverter noise, everything working fine .thanks
Swagatam says
tinuke, try placing an inductor and capacitor network across the output winding of the trafo…..you can take the help of the concept presented at the end of this article, in the magazine page snippets
https://www.homemade-circuits.com/how-to-make-simplest-inverter-circuit/
Reoc says
Swag,
Everything is working very fine now. At first, I used IRF250 as my power MOSFET (one for each arm of the switch).
When I tried using 100N25 (two for each arm of the switch), the MOSFETs burns out. I have repeated this and the MOSFETs kept burning.
Whenever I revert to using a single IRF250, the inverter works very fine.
Can you please advise me on what to do, thank you.
Swagatam says
Hi Reoc, if one type of mosfets is working and the other not working then clearly the one which is not working could be a non-compatible type for the present application…or possibly those are faulty originally…
can you please tell me the voltage and current specifications of the bad mosfets from its datasheet, that will help us to confirm the tests.
Reoc says
Hi Swag,
From my observations, it seems like the burning MOSFETs were not clamped firmly to the heatsink. I believed this because any of the MOSFETs clamped firmly to another heatsink works very well.
I want to know if this can cause them to burn out.
Swagatam says
Hi Reoc, that may be possible, however mosfets are positive-temperature-coefficient devices, and therefore will normally try to shut-down as its core temperature increases, so a loose clamping may result in poor efficiency, but not in the burning of the mosfets…there could be some other potential reason.
Reoc says
Hi Swag,
What can cause my MOSFETs to burn within 5 Seconds?
I am using a gate resistor of 22ohm and I connected a 10k resistor between the gate and the source. Please help me out, thank you.
Swagatam says
Hi Reoc, if its blowing even after connecting everything correctly, then the possible cause could be the reverse spikes from the trafo winding…try installing rectifier diodes across the cathode/anode of each mosfets and see if that helps.
Reoc says
I discovered that there was a dry joint (not properly soldered) in one leg of the SG3525.
I have soldered it well but there is another problem, the 22ohm resistor connected to the gate burns out after a short time.
Please can you help me by suggesting a solution to this, thank you.
Swagatam says
22 ohm is the gate resistor which should never burn because mosfet gates have a high impedance, it seems your mosfets are damaged or faulty originally.
Reoc says
Will the circuit work if the duty cycle of the secondary PWM is 50%?
Swagatam says
which secondary PWM?
Reoc says
I mean the PWM of 400Hz, I was asking if the system will work when the duty cycle is 50%.
Swagatam says
it can be 50% or any other value depending on your transformer specs, you can tweak the duty cycle to adjust the RMS and also the output wattage.
Reoc says
Hi Swag, I think when the frequency of the second PWM is 200Hz, it will only chop the primary wave into two. For you to chop it into four, the frequency of the second PWM must be 400Hz. I just simulated it. Please correct me if I am wrong.
My question is, is there any advantage or disadvantage of given a feedback voltage to pin 1 of the primary PWM for voltage regulation?
Swagatam says
Hi Reoc, Let me analyze it:
50 Hz corresponds to 10 milliseconds, 200 Hz corresponds to 5 milliseconds, during each 10ms ON time of each mosfet, the PWM would chop this 10ms pulse with 5ms ON/OFF periods, which will result in 2 ON and 2 OFF pillars, that’s 2 pillars for each 50 Hz, so it seems you are right it should be 400 Hz for generating 4 ON time pillars on each of the 50 Hz cycles.
Swagatam says
considering the RMS is dead fixed, the feedback becomes unnecessary, because the output would be always constant regardless of the load, unless the load exceeds the inverter’s max wattage limit, or the battery goes below the acceptable discharge limit.
Saqib Lodhi says
Hi Swag,
Hope you are doing well. One question. What should be the frequency of SG3524/25 on its pin 11 and 14 if I require output of 50Hz. I assume it should be 100Hz because there is a switching between these pins.
Swagatam says
Hi Saqib,
it should be 50Hz according to me….50 Hz corresponds to 20ms, therefore 20ms wave pulse on each of the pinouts will allow a +/- 50Hz waveform at the output
Saqib Lodhi says
OK. second inverter using SG3524 is almost ready. but I am having an issue. one of the mosfet is heating up without any load in 5 to 20 seconds. while the second one is cool. and transformer giving little noise. Can you please guide me from here. SG3524 is powered on with 8 volts using 7808 and 547/557 are powered on using 7812.
Swagatam says
If the IC powered with 8V then the emitter of BC547 will also create 8V, infact only 7V which could be quite low for the mosfet, feed the IC also with 12V and check the response, and anyway an extra 7808 is simply not required, you can use the single 7812 supply for the complete circuit stage.
Saqib Lodhi says
Tried it. but dont know what happened. IC is oscillating correctly. I am getting 5+ volts on pin 11 and 14. Mostfets are cool. 13.4v on center point of transformer. BUT output is zero. transformer isn’t making any noise seems not working anymore. I am trying to find out the reason. any quick suggestion?
Swagatam says
use 12V motorcycle bulbs in series with the mosfet drains, if they light up then the mosfets are working otherwise they are not.
if you BJTs in Darligton form you will get guaranteed results.
You can try TIP122/TIP35 in Darlington combination on each channel…the results will be immediate with 100% success.
Saqib Lodhi says
I dont have motorcycle bul. Any replacement. And do you have any example for whatever you have said for BJT and TIP transistors?
Swagatam says
you can any 12V 2 amp bulb for the testing.
for the Darlington, connect the base of the TIP122 with the IC output, connect its emitter with the base of TIP35, connect the collector of TIP122 with the collector of TIP35, connect the emitter of TIP35 to battery ground…the collector joint of the transistors will go to the trafo tap
Saqib Lodhi says
Can I feed TIP122 base with output coming from emitters of 547 and 557 so I will require a small PCB in addition to whatever I have printed already.
Also can you please confirm for any replacement in case of unavailability of TIP122/35. I have to go market to get them.
Also do you think there is a way to join any two transistors to get same functionality as these TIPs?
Swagatam says
547/557 will not be required if mosfets are not used, you can directly feed the IC output to them.
TIP122 is a Darlington but it is not necessary, any ordinary 2 amp NPN transistor can be used for TIP122
For TIP35 you can use any 25 amp NPN power transistor or as per the output wattage of the inverter
Swagatam says
please see the last diagram from this article, you can configure the transistors in this manner
https://www.homemade-circuits.com/2013/10/making-3kva-modified-sine-wave-inverter.html
Swagatam says
but in the particular configuration as given in the linked diagram, TIP36 is used which is a PNP
tinuke says
Well done sir, please I built a modified inverter of 24v(2kva) and 36v(3kva) input, both when used to carry pump 1hp draw almost the same current (20amps,dc), what could be wrong .
Swagatam says
current consumption will depend on load specs not on inverter specs
Reoc says
Hello Sir,
Please what is the frequency of the additional PWM?
Is it 200Hz or 400Hz?
Swagatam says
Reoc, are you referring to the fast triangle waves? you can select it as per your own comfort, it can be 4 times the slow frequency or 10 times…but higher difference will cause higher harmonics and will require more sophisticated filter for cleaning it up….but higher frequency will also enable more improved sinewave replication
Reoc says
Sir,
I am talking about the frequency of oscillation of the 555 PWM.
Thanks
Swagatam says
The answer is identical to my previous response, it can be 200Hz, or 1000Hz.
Swagatam says
yes, that’s right 1K0 = 1K
yemi says
Please between modified and pure sine wave inverter which one is more efficient
Swagatam says
both will be efficient, but pure sine will be more suitable for the appliances.
Swagatam says
…yes you will be able to get a sinewave after suitable filtration at the trafo output
Reoc says
Sir,
Thank you for your reply.
From your reply, does it mean that I need a transformer of 24-0-24, if my battery bank is 48VDC?
If your answer is yes, please explain the reason to me.
Must the filter capacitor be that value in your diagram? What if I reduce or increase it or completely remove it?
Also, is there any need for a feedback to pin1 of the primary sg3525 for voltage regulation?
Swagatam says
Reoc, yes that’s correct, due to the PWM chopping the average battery voltage will be reduced across the trafo primary which will result in a dropped voltage at the output, to compensate this loss the primary should be also equivalently reduced to match this.
you can read the following article for more info
https://www.homemade-circuits.com/2017/07/inverter-voltage-drop-issue-how-to-solve.html
the filter capacitor will need to experimented for achieving an optimal outcome!
pin#1 PWM control can be eliminated or ignored if the IC 555 PWM is incorporated.
Reoc says
Already, I have a working PWM inverter based on SG3525 that I want to upgrade to a sinewave inverter. Thank you for the knowledge shared on this web page.
1. Can I use a second SG3525 PWM whose frequency is 200Hz, from pin 4 to power the lower side of the circuit (I mean the signal that divides the original signal into 4)?
2. Concerning the transformer, should I use ordinary 12-0-12, 220V transformer?
Swagatam says
yes that’s possible, you can use another SG3525 for generating the 200Hz PWM chopping, but the same can be done using a simple and cheap IC 555 circuit
The inverter transformer must be rated at 6-0-6V/220V if the battery is 12V, the wattage of the trafo should be appropriately selected as per the requirement.
Godson Ugo says
Hello sir Swagatam, I must say that you are doing a great job in educating electronics hobbyists. Keep up the good work sir. I’d like to ask some questions sir.
1. From the schematic above, you used a fixed resistor as Rt instead of a pot. I’d like to know why sir.
2. Can the schematic above be upgraded to construct an inverter up to 10KVA merely by increasing the number of MOSFETs, size (power rating) of transformer and battery voltage as explained by you in the comments without any modification? If no, what is the maximum capacity that can be built from the schematic and what modifications are required to upgrade it up to 10KVA or above?
Anticipating your response. Thank you sir.
Swagatam says
Hello Godson,
the last schematic was taken from the internet, it is not my design, I have just provided an example design which can be integrated with the first PWM controller stage. If you wish you can change the Rt with a preset, or you can even replace the entire SG3525 stage with your own SG3525 version.
you can upgrade the above design or any inverter design to any desired level, simply by upgrading the mosfets, trafo and the battery proportionately.
You can add as many mosfets you want in the design for upgrading its handling power.
Godson Ugo says
Thanks so much for your prompt response sir. I sincerely appreciate it. I still need you to help me with the answers to the following questions:
1. I’d like to use your own design, the one in “Modified Sine Wave Inverter Circuit using SG3525”, which has low battery auto-power off and automatic output voltage regulator. But in the comments, you said that the voltage regulator can be removed since voltage can be controlled with the preset in the PWM session. Please I need you to confirm that sir.
2. As regards the upgrade of the schematic, please I need you to help me with how to calculate accurately the number of mosfets per transfo capacity per battery voltage. Say for example, for a 1KVA inverter using (IRFP150N), I can use six of the mosfets, (three on each side) with a 9-0-9V transfo (as recommended by you) and powered with a 12V battery. Is there any formula to use for the calculation? If yes, kindly help me with it and if no, I’d like to know how to get the combination correctly.
Thanks a lot sir.
Swagatam says
Thanks Godson,
yes a voltage regulator may not be required if the PWM is correctly adjusted and remains fixed at that level. however if the voltage drops due to heavier loads then that cannot be corrected by any means…expect by enabling further upgrades to the trafo and the batt.
number of mosfets can be simply calculated by dividing the max output wattage by the mosfet amp rating, making sure that the voltage rating is correctly selected as per the battery level.
Godson Ugo says
Thank you very much for your response sir. But I didn’t quite understand the last sentence: “number of mosfets can be simply calculated by dividing the max output wattage by the mosfet amp rating, making sure that the voltage rating is correctly selected as per the battery level”, especially the last part of the sentence. I’d really appreciate it if you could shed more light on it, possibly with an example. Please pardon me, I’m quite new to inverter construction. Thank you sir.
Swagatam says
Godson, from the datasheet find out the “continuous drain current” or Id rating. then divide the wattage which you intend to have at the inverter output with this Id value.
Arjit says
Find = GND
Arjit says
Sir I have seen a 555 based ac inverter circuit in this circuit C L C π circuit are connected between transformer Driver (Bjt) and primary side of transformer indu used in series and its caps respect to find, can I use this cap indu cap π circuit with 3525 for accurate 50 Hz pure sine wave ??????
Swagatam says
Arijit,
the frequency input to the primary side must be a PWM based, only then your filter design will work to create a puresine, for an ordinary sg3525 design this arrangement won’t have much effect.
Anthony Ekoe says
Good morning Swagatam,
I need a very sensible circuit for power inverter A.C. output protection which would respond to all loads.Only for short circuit due the use of economic bulbs. Secondly what can I use when testing a pure sine wave inverter if don't have oscilloscope.
Swagatam says
Anthony, presently I do not have this circuit, if I find one will update it.
only an oscilloscope can be used for testing waveform, there's no other alternative
Swagatam says
thank you,
however 225 watts from 210 watts is not possible, you calculation may be incorrect.
you can high efficiency inverter by using a ferrite core trafo, full bridge topology and a li-ion battrey
Joe Adeoye says
Hi swagatam, its me again joe, I am working on a new project and i need your help cos i got stucked somewhere. I am working on a transformerless inverter. As we all know that, a transformerless inverter requires high-voltage DC to be fed into H-Bridge in the desired waveform. Fine, I have chosen EGS002 as my DC-AC SPWM driver, now before i can use it, i need to generate 250V DC or above from a 12V battery. Now, i opened up an abandoned transformerless inverter, i removed the ferrite core "color yellow" transformer inside, so as to use it to generate High Voltage DC. I choose IC 4047 as my oscillator. This small ferrite core transformer is a center-tap transformer, so, i configured my IC4047 to oscillate at 5KHz, and i used 10 Ohms resistor to the gates of my FETs, with a reverse diode (1N4148) connected in parallel with the resistor to aid the quick discharge of the gate capacitor inside the FETs, so as to improve the performance of the mosfets. At the output of the ferrite core transformer, i placed a bridge rectifier (Using 4 pieces of 5 Amps Thick diodes) with a 400V 120uF capacitor. Note that the circuit is made in a Push-Pull manner (i.e. 12v connected to the center-tap, and mosfets placed on right and left hand of the trafo).
When i powered the circuit, it works and on my meter i saw around 270V DC. But, here is the problem
I am using IRFP250 mosfets and the get HOT within 5 seconds of operation, i mean, really hot. The heat sink get really hot, so i quickly remove power. Please, how do i correct this problem. Thanks
Swagatam says
Hi Joe, that could be happening due to mismatched frequency and turn ratio of the ferrite trafo, try increasing the frequency and see if that improves the situation.
Joe Adeoye says
Sir, i have done as you said, i increased the frequency from 5kHz to 60kHz, i can see improvement in the performance of the circuit. The ferrite trafo did not buzz again and the temperature is normal, the mosfets too, they still get hot, but not like before. there is an improvement. they get hot within 30 – 45 seconds of operation. unlike before which gets hot immediately. Is 60kHz enough? or i should still increase it??
Also, i noticed IC4047 that i am using is not too good for high frequency oscillation, i checked on my scope, the wave form is bad, the higher the frequency, the uglier the wave form, i noticed that after 10kHz, the wave form is no longer square wave, it turns to an ugly triangle wave on my scope. I think this wave form can damage a mosfet quickly because it is not a pure square wave. I think i will need to change my oscillator to 3524 or i should use an op-amp for oscillation. Please i need your advice…
Swagatam says
Joe, 60kHz is Ok, I have see some inverters even using upto 100kHz, so that's fine….and the voltage also plays an important, you can try varying the voltage slightly also, which will give you an idea regarding the correct proportion and relationship between frequency, voltage and turns, once you get the right match you can alter the parameters with different proportions as per your specifications. for the mosfets try using a buffer stage as explained n the above article, or if you want to avoid this, you can add reverse diodes parallel with the gate resistors which will help the mosfets capacitance to discharge quickly and reduce malfunctioning chances…make sure the gate resistors are not above 20 ohms
Joe Adeoye says
I have 10 Ohms to the gates of the FETs and also i have reverse diode parallel to the 10 ohms resistor. I have introduced the buffer stage like you suggested and changed the fixed resistor of 4047 to a 10K POT so that i can vary the frequency. I tested the circuit and the result was amazing. First, i vary the 10K POT so that i get constant 20kHz and i test, the result was awesome, FETs worked upto 2mins before getting warm (Not HOT), i think this is normal, also, there is no huming sound, everything is cool. I tried to vary the POT again, and i noticed that, anything below 20kHz, the traffo will produce a humming sound and FETs will get HOT, but 20kHz, working condition is normal. But i am faced with a new problem. I dont really know if it is a problem. The output voltage on my multimeter reads 550V DC (on no load). I am not sure if i add a load, maybe it will go down. I have a bridge rectifier and 450V/150uF cap at the output. I noticed that the voltage is even above the voltage of my capacitor. I examined the temperature of the capacitor, and its normal, not hot, not warm. I am confused, i don't know if i can proceed by making use of this 550V DC and feed into h-bridge. Please advice me.
Swagatam says
Joe, a meter might produce confusing results while measuring high frequencies from an inductive system. if you check the peak and the RMS with a scope you will surely find it to be correct and as per the expectations.
and yes it will become normal as soon as a load is connected
Joe Adeoye says
Sir, you said "if you check the peak and the RMS with a scope you will surely find it to be correct and as per the expectations" how do i do this? The voltage (550V) is too high for my scope and will damage my scope. In the user manual of my scope, it says maximum voltage of 50V AC or DC. How do i test it on scope??
Swagatam says
Joe, 550V is not the correct reading from the meter, your trafo is rated to generate 330V from a 12V input so 550V is not possible.. that is what we want to confirm from the scope. you am verify the same by connecting a small load of 10 watt….
you can use a small 0-12V/220V trafo and step down the output of your inverter, and then measure the 12V side with your scope, this will you to get the proportionate value, which can be then used for calculating the peak and RMS of the inverter through simple cross multiplication
Joe Adeoye says
Sir, i have not completed the inverter, I am still working on the DC-DC converter, after getting it right, i'll do the DC-AC conversion. That was why i asked that, with the information i have now, can i proceed by using this voltage for my h-bridge dc-ac? Should i proceed?
Swagatam says
once you confirm the 330V DC output from the ferrite trafo you can proceed as per the steps.
Joe Adeoye says
Sir, How do i confirm 330V DC?
You said:
550V is not the correct reading from the meter, your trafo is rated to generate 330V from a 12V input so 550V is not possible.. that is what we want to confirm from the scope.
YES, I agree, but my scope cannot measure any voltage above 50V, otherwise, it will explode.
You said:
you can verify the same by connecting a small load of 10 watt….
I don't have any electronic device that run on high volt DC, max DC electronic i have is 12V DC and also, the AC load i have is 50-60Hz and cannot run on such high frequency i'm operating. So, i cannot get a load to test.
You said:
a meter might produce confusing results while measuring high frequencies from an inductive system
Yes! i totally agree with you. But how do i get the "ORIGINAL" voltage readings?
What i did, i placed one multimeter at the output of the ferrite before the bridge rectifier to measure the AC voltage and another multimeter after the bridge rectifier to measure the DC voltage. The first meter measuring the AC fluctuates between 170V AC – 240V AC, while the second meter measuring the DC stays constant at 600V DC. The capacitor after my rectifier is 450V/150uF. Now, my conclusion is:
AC voltage reading fluctuates because the frequency is too high for the meter to handle
DC voltage is showing such high voltage because, no load is connected and also, the capacitor might also store and store and store more energy that is not been utilized.
So, my assumption is, i think the circuit is safe to operate (just a guess), since the AC voltage is between the safe voltage (even though its not 100% true).
Sir, that is my assumption, please correct me if i am wrong.
Swagatam says
Joe, you can connect a 10 watt incandescent bulb as the load and then check the parallel output with the meter, I am sure you would have a small 220V/10watt or 25 watt incandescent bulb with you or you can procure it from the market.
the bulb will operate on both AC or DC without issues
Adeoye Joshua says
Sir, i have just ordered two incandescent bulbs. Those bulbs are not available in my country, so i have to order it on xxxxxxxx and ship to my country, to it took a month for it to arrive here. Now i have those bulbs, and i test it on my circuit. Without the bulb, like i said earlier, my multimeter reads 600V DC steady and mosfet gets hot in less than two minutes. Now i got 220V-240V 40W incandescent bulbs and i connected one to the output of the DC, and power the circuit, the bulb came on fully and i got 260V DC steady on my multimeter. The circuit operation got better with load connected. Mosfets only get warm and not hot, everything is cool and i am very happy. Now, i want to perform another test, to be sure i am not getting too many voltage drop. I connected the second bulb to the output, now, i have two bulbs at the output with 40W each, now i have 220V and 80W load, and i power the circuit. The two bulbs came on FULLY, and i still have around 245V DC on my multimeter. I was very happy and dancing… I want to double the ferrite core traffo so that i can have more energy, cos the ferrite core traffo i have can only give me around 500W max, so if i double it, i can get 1000Watt. I am very happy….
Swagatam says
That’s great achievement Joshua, congrats on that.
yes you can try upgrading the winding by using a bifilar coil and by increasing number of strands in this bifilar winding, this will help you to achieve more power at the output, but make sure that the battery is also appropriately upgraded, along with the mosfets.
Swagatam says
…but you must confirm with at least 400 watts…100 watts is simply not enough
Swagatam says
better to confirm first and then proceed with the next stages…you can do it in the above method, or using the step down trafo method.
OLUPOT DANIEL says
hello sir thanks alot yesterday i ran the first on my inverter that i have been making. the bulb was lighting but the output voltage was less than i expected i want it at 240volts.i tested it with a 9-0-9 transformer using a 12v/7Ah battery. so what could be missing. thanks
Swagatam says
Hello olupot, if the load wattage is more than the transformer wattage and its supply wattage then the output voltage will drop, please go through all the previous comments to learn the exact details….
Anthony Ekoe says
Hello Swagatam, Sorry for my mistake I thought you have the previous message still.The pin#2 is connected to pin#6.Pin#3 of ne555 output is connecting to pin#3 of second I.c Sn7474 thanks. What about the 4047 circuit please sorry for the inconvenience I am causing to your blog am a starter in all.
Swagatam says
Hello Anthony, OK no problem, I only wanted to suggest that the 7474 IC is not required, it is unnecessarily making the circuit complex, you can get 5kva with any oscillator IC, such as IC 555 or IC 4047 or SG3525.
If you are interested to use the 4047 concept suggested by me earlier then you can definitely go ahead with it, it's perhaps the easiest pure sine wave wave inverter circuit you can get anywhere.
but please be cautioned that if your are a newcomer then you must first make an effort to understand all the associated theories thoroughly, otherwise success can be difficult to achieve.
Anthony Ekoe says
Dear Swagatam, Therefore please send me your e-mail so that I can post the diagrams. Am finding it difficult pasting through your comments block and if any direction as to how to go about it,help me.I use smart phone to do all my operation I don't go to cyber café.
Swagatam says
OK you can send it to homemadecircuits @ gmail.com
Anthony Ekoe says
Dear Swagatam, I did send the circuit diagram through your email about the inverter circuit I brought to yourblog for clarification (NE555&SN7474n system).You did request. And again another one about CD4047 schematic diagram. So I wish to know if you have got the circuits. GOD bless you.
Swagatam says
Dear Anthony, I did not find any email in my email ID, and by the way I don't seem to have any circuit using those two ICs mentioned by you at the moment, sorry about that.
Aabhishek Sharma says
I think transformer might be damaged.
Swagatam says
put 220V AC from input 220V side and check the 12V side with meter (AC)
if it shows 12V with load (12V bulb) then your is OK
….connect 220V with a fuse in series and and take all the due precautions
Aabhishek Sharma says
Hello sir, I tested transformer and put probes from centre tap to one side it shows 12v
And then from centre tap to other side (again 12v) after that I measure potential difference between both sides it shows 24v check link for 30seconds testing video https://plus.google.com/+AbhishekSharmatechperson/posts/KsC4NdgBLiG you will let know my English
Swagatam says
it means your transformer is good, the 600V reading in your meter is wrong, connect a 0.22uF/400V cap across the output of the trafo and check again, this might bring it down to 310V
Aabhishek Sharma says
Hello sir,it's good to hear, but why transformer is showing suddenly such a behaviour even with both versions of inverter and how multimeter could show wrong if it's showing true reading with mains supply but 500v to 600v with 12-0-12 10A transformer and 5amp transformer is damaged fully.
I was using 5Amp with square wave inverter since one year and suddenly.
Swagatam says
It's because mains AC is clean with no harmonics, whereas the AC from your square wave inverter may be accompanied with many disturbances and harmonics, causing a false reading on the meter, did you connect 0.22uF/400V capacitor at the output as I had advised you??
Your technician is not correct, transfomer are manufactured as per the frequency, not on the basis of square wave or sinewave…ask him to provide the technical reason why a sinewave trafo must be different from square wave??
Aabhishek Sharma says
Hi sir, I have tried 2.2uf 400v and 1.2 uf 400v capacitor as I was not having 0.22uf 400v as a result the battery terminal was giving spark but without capacitor the result was same 600v(with square wave only upper circuit) And as per your last comment statement"" It's because mains AC is clean with no harmonics, whereas the AC from your square wave inverter may be accompanied with many disturbances and harmonics, causing a false reading on the meter" I want to say that 1 year ago when I made only the square wave inverter from other site I had same multimeter and it showed 230v reading so why now new one will show false reading, I think there might be problems with transformer winding, as some days ago I told you that I had added mosfets in parallel which was 'not' necessary and both transformer made crispy sound so I think problems started from that time and now I prefer to arrange for a new transformer. I am using 555pwm, Now do favour suggest me a new transformer specs so that may fit according to the circuitry best with all measures.
Swagatam says
Hi Abhishek, I have already explained you regrading the transformer, please go back to previous article for all the details and also read the following article to know how the specs should be selected as per the PWM.
https://www.homemade-circuits.com/2017/07/inverter-voltage-drop-issue-how-to-solve.html
Joe Adeoye says
Not getting things right might be very frustrating and can make someone to cry. I could remember myself in this same kind of situation months ago, but with determination, i was able to solve the problem. The major point of all this issue is UNDERSTANDING… When you understand the circuit, you'll have no problem.
From this post, i think you're having problem with:
1. Voltage drop
2. Over-voltage at trafo output
3. Bad/damaged trafo
Let us look into the issue one after the order.
1. Voltage drop: This occur in 3 different ways. (a) If you use low rated transformer (b) If you use low amps battery (c) When your PWM is not well calculated. If these 3 are taken care of, then you should not have problem of voltage drop
2. Over-voltage: You need to understand that, a transformer is meant to step-up or step-down voltage. Thats all. Therefore, if you are getting high-voltage at the output of the trafo, then you need to check your input voltage. This is because, the output voltage will always correspond to the input voltage according to the number of windings. If you have a 12-0-12/220 transformer, if you feed in 12v, then you're rest assured that output is going to be 220v, and if you feed in 24v, then you should be expecting 440v at the output. So, if you're getting unwanted voltage at the output, then check the input voltage.
3. Bad/damaged transformer: I want to tell you that, a transformer cannot damage. A transformer is made up of coil and silicon sheet, thats it. There is no electronics that can get damaged inside a transformer. Even if the transformer over-heat and melt, it still keeps working until there is a mis-contact in the coil of the trafo.
In summary, to solve over-voltage problem,
1. Construct a simple square wave inverter using either 4047 or 3524 IC and use your trafo with it and measure the output voltage. DO NOT USE ANY CAPACITOR AS FILTER AT THIS STAGE.
2. If your output voltage is correct, then it means you need to do more precise calculations on your PWM circuit stage.
3. If your output voltage is NOT correct, then it means you need to check if your battery is fully charged, and if you are getting the correct voltage at the input of the trafo. Also make sure that you are using a THICK wire that can handle sufficient amps for the trafo and the MOSFETs.
After following these steps correctly, you should be able to solve your problem.
Joe Adeoye says
Also, concerning your engineer saying square wave inverter transformers are different from sine wave inverter transformers, i think that is wrong. Transformers are transformers, it is only winded in different ways depending on the need. Most pure sine wave inverters uses the Full Bridge (H-Bridge) Mosfet topology. So, the kind of transformer for H-Bridge has two input terminal, which means, there is no center tap. But the ones we do here, including the one i did for myself, i used a center-tap trafo because i am NOT using H-Bridge topology. So, transformers are not different. they are all the same.
Aabhishek Sharma says
OK sir,(1)I understood you mean to say the 600v output without using pwm is not transformer's fault and it is normal.(2)I need to regulate it using 741 ic. And with pwm ic 741 regulator is not needed. Is it all that you want to say? But earlier this was not happening.
Thanks
Swagatam says
600V is not OK, it should be 310V but previously it was showing lower reading so it seems your meter could be wrong, or the transformer could be originally of bad quality and might have got shorted because of some low quality winding….but normally a transformer can never get damaged without getting burned
Aabhishek Sharma says
Hi sir, ok I will follow your advice now tell me what is solution of my problems instead of buying new transformer what can I do if get 400v output should I use voltage correction circuit and are you sure voltage correction with that circuit will be best solution and not cause any problems. Please reply till night so that I could go to buy ic 741 from market.
Swagatam says
Hi Abhishek, all my solutions were the best solutions but you did not follow them so far…that's the reason you are still struggling with a simple inverter circuit.
Please note that I may not repeat what I have already explained you many times.
to get 400V you must use a lower voltage rated trafo than the battery voltage, but since you were not ready to buy a new trafo I suggested you to buy another battery and connect it in series with the existing battery, you did not do that, so please do whatever you may feel may correct, or you can read the links which I have already suggested you previously and advised you to first learn the concepts thoroughly and then move ahead….
Aabhishek Sharma says
PLEASE READ FULL…
hi sir , Currently I am not having voltage drop issue .please,And i dont want
400v(why i will wish for 400v i am already getting 600v) .From yesterday I am saying you that suddenly transformer started giving 500 to 600v.i have checked both of my inverters with same transformer and also with 5amp transformer result is almost same .AND EVEN WITHOUT PWM ALSO THIS IS HAPPENING.
I THINK YOU WERE UNABLE TO UNDERSTAND MY APPEAL.PLEASE READ FULL .
I DONT HAVE VOLTAGE DROP PROBLEM. PLEASE TELL WETHER THE TRANSFORMER IS FAULTY OR IT CAN BE CORRECTED THROUGH VOLTAGE CORRECTION CIRCUIT.my whatsap number is 8826825108.
Swagatam says
Hello Abhishek,
I have already explained you many times, and this is the last time I would be explaining, please write it down on a paper:
1) adjust the PWM to reduce the output voltage (RMS) to 240V, if PWM is not use then you can use the 741 IC regulator circuit to drop it.
2) if PWM is used make sure to connect a 0.22uF/400V or 0.33uF/400V or any such suitable capacitor to bring down the output to 240V even without load.
3) with PWM connected, if you see output dropping to 170V or lower then that could be due to low trafo current spec.
to correct the above voltage drop issue you can read the following article thoroughly and act accordingly
https://www.homemade-circuits.com/2017/07/inverter-voltage-drop-issue-how-to-solve.html
Swagatam says
correction 3) point:
with PWM connected, if you see output dropping to 170V or lower UNDER LOAD then that could be due to low trafo current spec.
Aabhishek Sharma says
Hello sir, I have checked multimeter with mains and it's showing 220v and 217v which is fine, are you sure the reason you mentioned are only to get transformer damaged and not the other reason ?Both The transformer never heated
And both inverters can't be false I'm feeling right now tired man, please read previous comments for more problems details this is first time in life I'm facing so much of problem in making something. Please help and don't get angry.
Swagatam says
Hi Abhishek, I am sure of that, before a transformer gets damaged it will emit smoke or at least emit a burning smell…even burnt trafos keep working until the winding is completely shorted…if you proceed with proper understanding and follow my instructions then I will surely keep helping otherwise I may lose interest….
if you are tired then you must quit electronics and stop pursuing electronics….
Swagatam says
Hi Abhishek, a transformer will get damaged only if it gets too hot and burns, there's no other way a transformer can get damaged…I think your meter is faulty, and malfunctioning
Anthony Ekoe says
Hello Mr Swagatam, I am at my wit end just the fact that I am not a skill type in electronic.Your circuit sg3525 pure sine wave, am still unable to get my 50hz frequency having done all I could with my little Automobile electric knowledge. Dear designer, inventor and public mentor, I wish to bring on your table an old power inverter circuit for your clarification, this I built several time. But it has very small output, since I began browsing through internet it has been my wish to build something more sophisticated.
My circuit consists 3 integrated circuit. A regulator 7805 battery power source feeding NE555.And output pin #3 of ne555 connect output pin #3 of the third I.c SN7474.And from pin #2&6 and pin#5 of sn7474 is 2(22k ohms) one connected to earth and through a transistor 2N2222A through 2(820 ohms) to second transistor BD136 and finally through a 33 ohms 5 watts and 100 ohms to 2 power transistors 2N3055 to a transformer input. Please, how do I increase this to 1000 watts output and a pure sine wave? Please help I know you are not waery of our long bothering questions. My dear to you my engineer.
Swagatam says
Hello Anthony, since I cannot see the schematic design of your inverter, it will be difficult for me to judge its internal functions and other related parameters, however power output of any inverter can be quite simply increased by adding more number of power devices in parallel at the output stage, ideally using mosfets, and along with this the transformer and the battery must also be proportionately upgraded to enable the power boost.
in your case it seems 2N3055 are used, which I am afraid doesn't look be an appropriate candidate for enhancing power upto 1kva even if more number were added in parallel.
you must select a mosfet based design for implementing the suggested upgrade, or replace the 2n3055 with mosfets, so that these can be added in parallel for achieving the intended output level, not forgetting the trafo and battery specs
drahcir _26 says
MR. Joe Adeoye!you save my day! i am now totally understand why too much voltage drop when connected any pwm method to make the waveform similar to sinewave. now all i need to do is use OP-AMP as SPWM and use 6-0-6 transformer.
MASTER SWAGATAM! can i use ic556 to generate both slow and fast triangle-wave?
Swagatam says
Thanks Dracir, yes you can use a single IC 556 configuration and you can collect the two frequencies from across the two respective timing capacitors.
However, the type of PWM is not the culprit, it's the duty cycle adjustment that affects the output, so you
must understand how the PWM functions and how it must be optimized to get the correct
results from it.
without PWM the duty cycle is 50%, therefore if you multiply the battery 12V with this 50%
you get 6V, multiply this 6 with the current consumption, say for example 10 amps (for a
10amp/0-12V trafo), you get 60 watt as the answer, for both the halves this becomes 60 + 60 = 120 watts, that's exactly what your rafo is rated, therefore you are able to get full output.
suppose you are using a PWM 50% duty cycle, and you apply it to the gates of the mosfets, this will cut the already present 50% duty cycle further down to 25%, therefore your output will become 60 watts instead of 120 watts.
Therefore it's not the type of PWM that matters rather it's how you optimize it makes the difference.
Swagatam says
Hi Drahcir, in one of your recent comments you asked whether an SPWM would overheat the mosfets or not, the answer is no, it won't if you use the BJT buffer stage as indicated in the above article, and if you keep the PWM frequency low, meaning use just 3 to 4 pillars for the SPWM , this will keep the harmonics within limits and prevent the mosfets from getting hot.
drahcir _26 says
https://cdn.instructables.com/F3U/90GJ/H82U2ARE/F3U90GJH82U2ARE.LARGE.jpg
this is my current inverter. master pls help me how to incorporate with you pwm method on this circuit, my english is poor pls understand.
Swagatam says
you just have to replace the mosfet section of your inverter with the first diagram as shown in the above article.
Swagatam says
you can refer to the following article for the details
https://www.homemade-circuits.com/2017/06/sinewave-3kva-inverter-using-sg3525.html
drahcir _26 says
so why theres no voltage drop when i disconnect the pwm to chop the waveform? i will try to measure the ampere next time i will update you soon, and i try to change the load with 40w incandescent bulb. maybe my analog multitester confuse on monitoring the current voltages.
Swagatam says
it's because chopping is cutting out the sections from the original square wave leading to reduction in current… this has to be compensated by using higher current winding at the primary side so that the winding can absorb optimal current from the high sections of the chopped waveform.
Joe Adeoye says
Also, do not use IC741 OP-amp because it requires positive and negative voltage to power it. You can use LM324 or 358 which can be powered using a single source
Swagatam says
Hi Joe, I accidentally deleted your previous comment, but fortunately I had the copy saved in my email, so I am copy pasting it below for benefiting the other readers:
Swagatam says
Advise from Mr. Joe
Good day drahcir, I have been in your shoes before suffering from voltage drop problem after introducing PWM to the square wave from 3524 IC. It took me weeks for me to be able to figure out and resolve the problem. The problem i had then is that, using a normal square wave, after connecting load, the voltage still remains at 220v which is pretty good. But when PWM is introduced, whenever i connect load of 60Watt, the voltage drop by 50% i.e. from 220v to around 110v. Taking time to understand what is going on helped me to resolve this problem. First thing you need to understand is how the PWM works, when pwm is not introduced to your square wave, you have your FET turned on for 20ms and off for 20ms (if working with 50Hz) which in turns gives you the desired output. Now, when pwm is introduced, like for example, using 200Hz pwm which divides your square wave into 4 segment, you notice that the ON and OFF time has been reduced by 50% i.e. dividing 50Hz into 4 pulses, you have 2.5ms ON and 2.5ms OFF for 4 times, adding 2.5ms * 4 gives you 10ms ON and 10ms OFF, which originally was 20ms, which will cause your output voltage to drop by 50%. This is why it is always recommended to use a 6-0-6 traffo for 12v power supply, or 12-0-12 traffo for 24v power supply which will help you get your full output voltage.
Now, concerning the voltage drop, from my experience, the filter i was using is causing the problem. Normally, after applying PWM, you need some filter at the output of the traffo in order to filter out harmonics, if no filter is used, you'll get some funny readings from your scope and endanger loads connected to traffo output. In my case, i was using 1uf/400V capacitor as filter. After adjusting the pwm POT, i got a clean sine wave from my scope at desired voltage but when i connect load of 60W soldering iron, voltage drops to 120V. The problem there was that, the filter i used was deceiving me, i.e. giving me wrong voltage readings on my multimeter. After setting the PWM POT and getting a clean sine wave, i removed the filter and check the voltage on my multimeter and i discovered that it was around 190V, and when i add the filter again, it jumps up to 240V which was a *FAKE voltage.
So, the thing is, i wasn't really getting the voltage i thought i was getting as output voltage and which is why the voltage dropped at high rate, because, powering a 220V load with 190V source, leads to insufficient voltage and in other to complement the voltage, it will draw huge amount of current which will also reduce the voltage the more.
I have tried several PWM with no success, i am ALWAYS faced with this same challenge.
One day, i came across another PWM circuit on this blog which saved my life. If you scroll up, you will see another PWM circuit, using Operational Amplifier (OPAMP), to generate SPWM, all you need to do is know how to generate a triangle wave which is quite simple, generate a fast and slow triangle wave and feed them to the input of an Op-amp, and it will give you some sort of SPWM which you can use. Note that the *slow triangle wave form must be 2 times your original frequency e.g. 50Hz for 100Hz triangle wave. And the *fast triangle wave shouldn't be less than 2KHz, otherwise, your output sine wave won't be *pure. As for me, i used IC 4047 and i used the PIN 13 to generate the triangle wave for the *slow wave fed into op-amp. This gives me 100% accuracy on the TIMING.
So, to summarize the whole story:
1. Check your output voltage when you remove your output filter
2. Connect a little load (like a soldering iron) without filter and read the voltage again
3. Connect your filter and read the voltage
4. With filter connected, connect your load and measure the output voltage again.
As for me, the SPWM circuit saved my life and working pretty fine using 2.2uf/400V cap as filter.
WARNING: Do NOT connect any surfisticated electronics as load. Always use something like a soldering iron as load during test.
drahcir _26 says
[URL=s1077.photobucket.com/user/drahcir26123/media/testing_zpsvx2lii0a.png.html][IMG]i1077.photobucket.com/albums/w475/drahcir26123/testing_zpsvx2lii0a.png[/IMG][/URL]
Master if i slow down the pwm to 300hz the waveform chopped into 4 times, and the voltage drop form 220vac to 140vac with the load of 40watts soldering iron. i think if we use this pwm method on h-bridge orientation this will reduce the quality vs efficiency.
Swagatam says
Hello, the voltage drop may happen due to the following reasons:
incorrect PWM duty cycle
insufficient transformer, battery current output.
you can correct the issue by connecting an ammeter in series with the battery, and then adjust the duty cycle of the PWM until the optimal current is reached and the voltage is raised upto the desired limit.
basically insufficient current from battery or insufficient trafo saturation is main factor that leads to voltage drop
Swagatam says
pwm has nothing to do with efficiency..we are using PWM here just to "soften" the square wave DC output in terms of correctly regulated RMS value, so that it can reach close to the sine RMS value
Anthony Ekoe says
I build this circuit with difficulties,and I ended up getting 225volts but output frequency was 150hz and fluctuating down continually not stable. My Major problem was Ne555 p.w.m circuit finding the 200hz.I finally had by try and error way.So Mr Swagatam, please help me find it easily by giving me the exact values of the two capacitors in pin5,pin 2&6, of ne555 or help solve the problem. Operation sound rough.thanks God your blog.
Swagatam says
you can build any SG3525 circuit, and integrate it with the PWM, it is not necessary to build the one which is shown in the 4rth diagram fro top.
200Hz is also not a mandatory figure, it can be 300 Hz or 400Hz also, 200Hz was chosen to keep the harmonics at minimum.
Pin#5 capacitor is always 10nF, pin#6/2 capacitors can also any arbitrarily selected value, such as 1uF/25V…the other values can be adjusted by using the following software (second option on the page)
https://www.homemade-circuits.com/p/ic-555-calculator.html
the 150Hz reading is incorrectly shown by your meter, it's probably the PWM frequency which is being caught by the meter, using an oscilloscope to check the exact frequencies.
Ravindra Balme says
hell sir thanks for sharing your knowledge with us…..i have made this circuit but i didn't get any output please suggest me what can be done??
Swagatam says
Hello Ravindra, it would be difficult to troubleshoot your circuit because I cannot see what mistake you might have made in your.
I would suggest you to first learn all the basics and then build a simple SG3525 inverter, after that you can go for the PWM integration as instructed in the above article.
Anas Ahmad says
hello good day, i didnt see your replies, hope am not disturbing, like i said am a novice
Swagatam says
Hello Anas, I have transferred our discussion into this post, you can carry on the discussion under this article
https://www.homemade-circuits.com/2017/06/sinewave-3kva-inverter-using-sg3525.html
Adrees mohmand says
Sir i have an idea in my mind. if i increase the dead time more and more, Is this decrease the pulse width.?