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You are here: Home / Inverter Circuits / 3 High Power SG3525 Pure Sinewave Inverter Circuits

3 High Power SG3525 Pure Sinewave Inverter Circuits

Last Updated on February 20, 2021 by Swagatam 840 Comments

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.

Warning: If you are using SPWM as the input, then please replace the lower BC547 with BC557. Emitters will connect with the buffer stage, Collector to Ground, Bases to SPWM Input.

As may be in the above diagram, the lower two BC547 transistors are triggered by a PWM feed or input, which causes them to switch according to the PWM ON/OFF duty cycles.

This in turn rapidly switch the 50Hz pulses of the BC547/BC557 coming from the SG3525 output pins.

The above operation ultimately force the mosfets also to turn ON and OFF number of times for each of the 50/60Hz cycles and consequently produce a similar waveform at the output of the connected transformer.

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.

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:

IC 555 pwm with pot and 1N4148

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:

generating sine pulse width modulation or SPWM with opamp

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:

THE FREQUENCY OF THE FAST TRIANGLE WAVES SHOULD BE AROUND 400 Hz, CAN BE SET BY ADJUSTING THE 50 k PRESET, OR THE VALUE OF 1 nF CAPACITOR
THE SLOW TRIANGLE WAVES FREQUENCY MUST BE EQUAL TO THE DESIRED OUTPUT FREQUENCY OF THE INVERTER. THIS MAY BE 50 Hz OR 60 Hz, AND EQUAL TO PIN#4 FREQUENCY OF SG3525

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:

Simple IC SG3525 inverter configuration

Complete circuit diagram and PCB layout for the proposed SG3525 pure sine wave inverter circuit.

Courtesy: Ainsworth Lynch

SG3525 chopped inverter using IC 555
PCB design of SG3525 inverter circuit

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:

SG3524 with BJT buffer stage

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

5000 watt SG3525 inverter circuit



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About Swagatam

I am an electronic engineer (dipIETE ), hobbyist, inventor, schematic/PCB designer, manufacturer. I am also the founder of the website: https://www.homemade-circuits.com/, where I love sharing my innovative circuit ideas and tutorials.
If you have any circuit related query, you may interact through comments, I'll be most happy to help!

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  1. Search Related Posts for Commenting

  2. Seun says

    Good day Sir, please what could be responsible for damage of fan used for cooling inverter

    Reply
    • 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….

      Reply
  3. 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

    Reply
    • Swagatam says

      4 x 40 Ah is efficient since higher voltage will mean lower current and thinner wires and smaller transformer

      Reply
  4. 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.

    Reply
  5. 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!!!

    Reply
    • Swagatam says

      Sorry, I do not use softwares, so no ideas!

      Reply
  6. Seun says

    Please Sir, please how can I add a cold start to the inverter circuit

    Reply
    • Swagatam says

      Seun, please explain the requirement elaborately

      Reply
      • 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

        Reply
        • 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

          Reply
  7. Godfrey says

    Please sir, can you help me with the circuit diagram for 200W pure sine wave inverter?

    Reply
    • Swagatam says

      Godfrey, the sine wave concept is already explained in the above article, you can easily customize them to your required specs

      Reply
  8. Godfrey says

    Please I want to find out information on the settings of the presets

    Reply
  9. 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!

    Reply
    • 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

      Reply
      • 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.

        Reply
        • Swagatam says

          OK thanks!

          Reply
          • 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

            Reply
            • 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://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

  10. 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.

    Reply
  11. 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

    Reply
    • Swagatam says

      Seun, 8 SWG looks OK to me for 5kva.

      Reply
  12. 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

    Reply
    • 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

      Reply
      • 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

        Reply
        • 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/

          Reply
  13. 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.

    Reply
    • 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.

      Reply
  14. Stephen says

    Hello
    Must the feedback transformer in the circuit must be 9v 100mah or is there any alternative

    Reply
  15. Akshaya says

    Can I use this circuit with 12v dc 7.2Ah battery.will it work then?

    Reply
    • Swagatam says

      yes you can

      Reply
  16. 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

    Reply
    • 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….

      Reply
  17. 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

    Reply
    • Swagatam says

      Hello Ehsan, what is the input voltage to the inverter, is it from 12 V battery?

      Reply
      • Ehsan Firouzi says

        Hi .the input voltage is 220 v AC

        Reply
        • 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

          Reply
  18. 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.

    Reply
    • 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.

      Reply
    • Adeyemi says

      Sir, between 220v and 200v ac output voltage, which one is better to set inverter for good efficiency and why sir

      Reply
      • 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.

        Reply
    • 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

      Reply
      • 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.

        Reply
        • 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

          Reply
          • 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

            Reply
  19. 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

    Reply
    • 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

      Reply
  20. Adeyemi says

    Hello, please can I tune this circuit to 30hz to us for my ac motor

    Reply
    • Swagatam says

      Please check the datasheet of the IC, if it allows 30 Hz then you can do it.

      Reply
  21. 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.

    Reply
    • Swagatam says

      Abiola, the BJT buffer stage can be used with any oscillator circuit, so there’s no issue.

      Reply
  22. 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.

    Reply
  23. parick says

    Good day sir
    please how can i give the above circuit a feedback loop to maintain the output voltage? Thanks.

    Reply
    • Swagatam says

      Parick, all the first 3 designs include an automatic feedback…

      Reply
  24. 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.

    Reply
    • Swagatam says

      Adeyemi, there could be a short between the winding of the transformer, or somewhere in the connections.

      Reply
      • 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.

        Reply
        • 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

          Reply
    • Adeyemi says

      Please for 1kva inverter what is the maximum load it can carry

      Reply
      • Swagatam says

        May be up to 900 watts

        Reply
        • 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.

          Reply
          • 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.

            Reply
    • 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.

      Reply
      • Swagatam says

        I don’t think that’s correct, because both are PWM based designs so their working principle should be almost the same.

        Reply
      • Adeyemi says

        Please how can I earth an inverter connection properly, thanks sir

        Reply
        • Swagatam says

          You can connect the transformer lamination and the inverter chassis with the earthing line.

          Reply
          • Adeyemi says

            Please where on inverter chassis can I earth

            Reply
            • 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.

  25. Olamide Emmanuel says

    Please do u observe that the capacitor increases the noise level?

    Reply
    • Swagatam says

      No it did not create any extra noise in my experiment.

      Reply
      • 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.

        Reply
        • 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/

          Reply
          • 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.

            Reply
            • 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.

  26. 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.

    Reply
    • Swagatam says

      Olamide, you can use capacitors at the transformer output to purify modified sine waveform

      Reply
  27. 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

    Reply
    • 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

      Reply
  28. 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

    Reply
    • 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/

      Reply
      • 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

        Reply
  29. 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.

    Reply
    • Swagatam says

      The concept of relay changeover will be exactly the same as described in my earlier full bridge suggestion.

      Reply
      • 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?

        Reply
        • Swagatam says

          You can search it online….or use an equivalent SSR.

          Reply
  30. 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.

    Reply
    • 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.

      Reply
  31. sayed says

    hi swag, the design with the spwm can support a load above 1000 W ?

    Reply
    • 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

      Reply
      • 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 ???

        Reply
        • Swagatam says

          Hi Sayed, it’s because the IC 555 capacitor charge and discharge happens between 1/3rd and 2/3rd supply levels.

          Reply
          • sayed says

            so the comparator dont work properly in this case !!!!

            Reply
            • Swagatam says

              It will work properly and create the PWMs perfectly…

  32. Lakew Kidane says

    Found it very attractive ,thankyou

    Reply
  33. 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

    Reply
    • Swagatam says

      Sunshine, please post the comment under a related article, please see the message which I have put just above the comment box.

      Reply
  34. 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?

    Reply
    • 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/

      Reply
  35. jon says

    thanks for share

    Reply
  36. 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.

    Reply
    • 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.

      Reply
  37. 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

    Reply
    • Swagatam says

      The battery voltage can be around 36V

      Reply
  38. 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?

    Reply
    • 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.

      Reply
    • 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.

      Reply
  39. 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

    Reply
    • 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.

      Reply
  40. 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…

    Reply
    • 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/

      Reply
  41. Dru says

    Hey shalom…could you please help me outdru with how to interface the egs002 with the sg3525 man…

    Reply
  42. 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

    Reply
    • 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/

      Reply
  43. 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

    Reply
    • 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.

      Reply
  44. 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

    Reply
    • Swagatam says

      Hello Emmanuel, it can be done by adjusting the dead time value of the SG3525 IC

      Reply
  45. 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

    Reply
    • 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

      Reply
      • 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

        Reply
        • Swagatam says

          grounding is done by the transistor. Any extra resistor across gate source will not make sense in the above linked circuit.

          Reply
          • Emmanuel Offiong says

            Alright sir thanks a lot for your support and god bless you for your good work

            Reply
            • Swagatam says

              My pleasure Emmanuel

  46. 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

    Reply
    • 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.

      Reply
      • 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

        Reply
        • Swagatam says

          No, It should be in SPWM form, not exponential, ….only spwm will work

          Reply
          • Emmanuel Etim Offiong says

            Okey thanks

            Reply
  47. 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 ?

    Reply
    • 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

      Reply
  48. 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🙌

    Reply
    • Swagatam says

      Glad you liked them, wish you all the best!

      Reply
  49. 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

    Reply
    • Swagatam says

      From output is better, and should be through an opto-coupler

      Reply
      • 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

        Reply
        • 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?

          Reply
    • Tolu says

      Please what is the likely standby current draw for a trafo based and trafoless 1kva inverter. Thanks

      Reply
      • Swagatam says

        A trafoless inverter will have negligible standby consumption compared to a transformer based inverter

        Reply
    • 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.

      Reply
      • Swagatam says

        Try connecting the inverter body with a good earthing connection.

        Reply
  50. Mathieu says

    Hello Swag deos the SG3525 can work with a 7809 voltage? my sg3525 cant work under 12VDC!
    thank you!

    Reply
    • Swagatam says

      Hi Mathieu, SG3525 will work with 12V and also with 9V, something may not be correct in your circuit!

      Reply
  51. 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?

    Reply
    • 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.

      Reply
  52. 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 .

    Reply
    • 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.

      Reply
  53. 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

    Reply
    • Swagatam says

      Do you get the noise without the IC 555 PWM?

      Reply
      • 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.

        Reply
        • Swagatam says

          Disconnect the IC 555 PWM link from the BC547 transistors, and check whether the sound still occurs or not?

          Reply
          • 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?

            Reply
            • Swagatam says

              If you have used a socket for IC 555 then removing from the socket will be enough

  54. Joseph says

    Please, can you give me the full circuit with H bridge with oscillator like sg3234

    Reply
  55. 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?

    Reply
    • 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.

      Reply
      • 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

        Reply
        • 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

          Reply
          • sayed says

            Hi swag,with 2uf capacitor at the output ,the output waveform looks like this:
            https://1drv.ms/u/s!AmpwfsAEQtshgnVdP0sNbxAWeKJD

            Reply
            • 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.

            Reply
            • 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.

  56. 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

    Reply
    • 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.

      Reply
  57. 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

    Reply
    • 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.

      Reply
      • 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.

        Reply
        • Swagatam says

          yes that’s right, just make sure to add 10K in series with the positive side of the preset for IC 741

          Reply
          • Osei Kwame says

            I hear you teacher and thank you very much.

            Reply
    • Osei Kwame says

      Sir Swagatam my greetings, I was away for sometime but I’m back and I just missed your teachings thanks teacher.

      Reply
      • Swagatam says

        No problems Osei, please keep up the good work!

        Reply
  58. sayed says

    hi swagatam , which circuit is fully tested that i can use it?

    Reply
    • Swagatam says

      Hi Sayed, all are fully tested you can choose anyone as per your preference.

      Reply
      • 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?

        Reply
        • 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.

          Reply
          • 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

            Reply
            • 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

        Reply
        • Swagatam says

          Thank you!

          Reply
  59. 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

    Reply
    • 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!

      Reply
    • Harun says

      How to calculate MOSFET in pallarel or how to know number of transistors that will give me 1500w for inverter

      Reply
      • 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.

        Reply
  60. 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

    Reply
    • 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

      Reply
      • Osei Kwame says

        Thank you teacher

        Reply
  61. 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

    Reply
    • 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.

      Reply
  62. 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

    Reply
    • 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

      Reply
      • 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 .

        Reply
        • 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.

          Reply
  63. 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….

    Reply
    • 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

      Reply
      • Sigifredo Cruz Rojas says

        thanks but why the duty cycle is the same with full load and with no load?

        Reply
        • 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?

          Reply
          • 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.

            Reply
        • 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/

          Reply
          • 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.

            Reply
            • Swagatam says

              Can’t say much about it! It will be difficult to suggest without seeing the full schematic diagram of the circuit.

  64. 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.

    Reply
    • 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.

      Reply
      • 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.

        Reply
        • Swagatam says

          You are most welcome Andrew, please keep up the good work!

          Reply
  65. 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

    Reply
    • 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!

      Reply
  66. 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.

    Reply
    • Swagatam says

      Christ, You can try the following circuit:

      https://www.homemade-circuits.com/48-v-inverter-circuit/

      Reply
  67. 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?

    Reply
    • 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/

      Reply
  68. 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

    Reply
    • 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!

      Reply
  69. 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…

    Reply
    • 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.

      Reply
      • 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.

        Reply
        • 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.

          Reply
          • 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

            Reply
            • 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

  70. 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…

    Reply
    • 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.

      Reply
  71. 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

    Reply
    • 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

      Reply
  72. Seun says

    Please, is waveform different at different inverter voltage output.

    Reply
    • Swagatam says

      It may vary a little at different voltages.

      Reply
  73. 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.

    Reply
    • 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.

      Reply
  74. 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..

    Reply
    • Swagatam says

      You are welcome!

      Reply
  75. Sunshine says

    Okay thanks.. Please help me with any good inverter circuit that can power small refrigerator.. May God reward you with good thongs

    Reply
    • 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/

      Reply
  76. 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.

    Reply
    • 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

      Reply
  77. 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.

    Reply
    • 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/

      Reply
  78. 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

    Reply
    • Swagatam says

      you will need a mppt or a buck converter controller, then you use the panel directly with the inverter

      Reply
      • 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

        Reply
        • 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

          Reply
          • Grace says

            Thanks creative Engineer, please give me a circuit to mppt and buck converter. I enjoy your educative site, thanks.

            Reply
            • 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

        Reply
    • 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.

      Reply
      • 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??

        Reply
        • Grace says

          I meant factory made pwm solar controller.

          Reply
          • Swagatam says

            what is the output and input voltage and current specs of the controller?

            Reply
            • 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.

      Reply
      • 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.

        Reply
        • Grace says

          Thanks Chief Engineer, please how this inverter circuit do power factor correction.

          Reply
          • Swagatam says

            Hello Grace, PFC is not included in these designs, these are just basic inverter modules.

            Reply
            • 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)

  79. 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.

    Reply
    • 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.

      Reply
  80. 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

    Reply
    • 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://homemade-circuits.com/wp-content/uploads/2012/05/transformerlessinvertercircuit.png

      Reply
    • Love says

      The standby current draw from my 2kva inverter is 0.68amps, please what will be likely standby current for 10kva inverter

      Reply
      • Swagatam says

        As per calculation it should be 5 times more, around 3 amps

        Reply
      • Love says

        Hello sir, please what are the factors affecting inverter standby current draw

        Reply
        • 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!

          Reply
    • Love says

      Good day sir, is possible to build 3kva/120v Inverter. Any drawbacks

      Reply
      • Swagatam says

        Do you mean 120V DC input or 120V AC output?? If its DC input then its’ great, higher voltage means better efficiency.

        Reply
  81. Love says

    Please how can I make a voltage stepdown for a 120v/10kva inverter oscillator

    Reply
    • Swagatam says

      Please provide more info!

      Reply
  82. Love says

    For the back emf, why didn’t it affect the utility supply

    Reply
    • Swagatam says

      utility supply do not work with circuits, they come from generators.

      Reply
  83. Love says

    Thanks for the advice, which one is electronic section,

    Reply
    • Swagatam says

      the oscillator section which creates the 50Hz.

      Reply
    • 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

      Reply
      • 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/

        Reply
        • 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

          Reply
          • 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.

            Reply
  84. 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

    Reply
    • 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

      Reply
      • Love says

        Is it 1000uf or 100, as seen in video, please how does this function to prevent back emf

        Reply
        • Swagatam says

          That’s a filter capacitor 2200uF for filtering interference and spikes not for back emf.

          Reply
          • Love says

            Thanks, please is it the MOSFET diode protection handle the back emf.

            Reply
            • 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.

        Reply
        • Swagatam says

          You can use a 12V 1 watt zener diode for the gate

          Reply
          • Love says

            Thanks, what of the drain

            Reply
            • 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?

  85. 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 🇹🇿

    Reply
    • 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

      Reply
  86. Love says

    Good day Sir, please what’s the function of lower bc547 transistors

    Reply
    • Swag says

      It’s for chopping the mosfet gate frequency into smaller blocks, so that the RMS waveform of the output can be set appropriately

      Reply
      • 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.

        Reply
        • 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

          Reply
          • Love says

            Thanks sir, please what is the relevance of the THD 8.8%. I have used LC filter.

            Reply
            • 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!

  87. 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.

    Reply
    • Swag 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.

      Reply
  88. 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 .

    Reply
    • Swag says

      Blessing, which schematic have you used? please show me the circuit diagram or the article link.

      Reply
  89. 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.

    Reply
    • Swag says

      Abbey which feedback connections are you referring to? Is it from the first circuit, at pin#2?

      Reply
  90. 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.

    Reply
    • Swag 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.

      Reply
  91. 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.

    Reply
    • Swag says

      Good day Abbey, it may work but may cause noise, therefore modified sinewave or pure sinewave is recommended.

      Reply
  92. 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?

    Reply
    • Swag 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

      Reply
  93. 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.

    Reply
    • Swag 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

      Reply
      • Swag 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.

        Reply
  94. 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?

    Reply
    • Swag 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.

      Reply
  95. 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?

    Reply
    • Swag says

      adjust the PWM pot appropriately to make it a modified sinewave.

      Reply
  96. 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.

    Reply
    • Swag 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.

      Reply
  97. 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?

    Reply
    • Swag 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

      Reply
  98. 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.

    Reply
    • Swag 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.

      Reply
    • Love says

      Hi Swagtagam, please what is the effect of using high value filter like 32uf in this inverter

      Reply
      • Swag says

        Hi Love, if you are referring to the transformer output capacitor, 32uF would waste a significant amount of power, not recommended.

        Reply
    • Love says

      Thank you for the update, please for 10kva/120v input, what are the modifications.

      Reply
      • Swag says

        upgrade mosfet and transformer rating accordingly.

        Reply
        • 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

          Reply
          • Swag 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.

            Reply
            • Love says

              Please how can I add a power saving mode to this design to conserve energy. Thanks so much Swag.

            • Swag says

              You can add this to your inverter:

              https://www.homemade-circuits.com/2015/07/no-load-detector-and-cut-off-circuit.html

  99. 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.

    Reply
    • Swag says

      Ekoe, the frequency of a pwm based inverter must be measured and confirmed using an oscilloscope, a multi-meter can give misleading results.

      Reply
      • 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.

        Reply
        • Swagatam says

          Hi Joseph, you can refer to the second circuit on this link:

          https://www.homemade-circuits.com/simplest-full-bridge-inverter-circuit/

          Reply
          • Swagatam says

            For sine wave you have to integrate SPWM at the low side MOSFETs

            Reply
  100. 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.

    Reply
    • Swag 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

      Reply
  101. 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.

    Reply
    • Swag says

      OK, thanks for updating the issue!

      Reply
      • tinuke says

        Hi sir, sorry I was trying to ask why the MOSFET blowing incident. Thanks

        Reply
        • Swag 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/

          Reply
          • 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.

            Reply
            • Swag 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.

            • Swag 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.

            • Swag 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.

            • Swag 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.

            • Swag 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.

      Reply
      • Swag says

        sorry I could not understand what you mean by “spurious sinewave”

        Reply
      • 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

        Reply
        • Swag 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

          Reply
          • 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.

            Reply
            • Swag 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

            • Swag 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.

            • Swag 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.

            • Swag 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.

            • Swag 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.

            • Swag 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

            • Swag 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.

          Reply
          • Swag 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.

            Reply
            • Swag 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.

  102. Ola says

    Good day swag, Can this circuit be modify to single transformer inverter, what are the components in modification? thanks

    Reply
    • Swag 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.

      Reply
  103. 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

    Reply
    • Swag 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

      Reply
      • Glory says

        Yet to get resolved, any other advice Sir.

        Reply
    • Glory says

      Which filter system is good for inverter output. RC or LC system

      Reply
      • Swag says

        LC is more effective as far as I know…

        Reply
  104. abioye says

    and sir can i use bc546/ bc547 because i could not find bc556/bc557 thanks

    Reply
    • Swag 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…

      Reply
  105. abioye says

    sir can pin 4 of sg3525 generate slow triangular wave form as you mentioned in one of your post

    Reply
    • Swag says

      the Ct pin (pin#5) is supposed to generate it…please confirm it with a scope first

      Reply
  106. 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

    Reply
    • Swag 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

      Reply
  107. 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

    Reply
    • Swag 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…

      Reply
  108. 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

    Reply
    • Swag says

      use a voltage regulator for the IC, such as a 7812 IC

      Reply
      • 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

        Reply
        • Swag 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

          Reply
          • Swag says

            55Hz may not be appropriate for any appliances

            Reply
          • Tolu says

            Please any circuit for the combination of sg3525 and 555 for better frequency output.

            Reply
    • 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

      Reply
      • Swag says

        which schematic are you referring you to?

        Reply
      • Tolu says

        The bjt/pwm stage in this page, the bc547/bc557

        Reply
        • Swag 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

          Reply
  109. 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.

    Reply
    • Swag 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…

      Reply
    • 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

      Reply
      • Swag 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

        Reply
        • Dayo says

          Please how does low battery affect it, because my battery is presently bad. Thanks.

          Reply
          • Swag 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!

            Reply
            • 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 .

        Reply
        • Swag 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…

          Reply
  110. 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

    Reply
    • Swag says

      sorry, I have no idea regarding the filter frequency…you will have to calculate it with thorough experimentation.

      Reply
  111. 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

    Reply
    • Swag 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

      Reply
  112. 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

    Reply
    • Swag 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

      Reply
  113. 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?

    Reply
    • Swag 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.

      Reply
  114. 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?

    Reply
    • Swag 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.

      Reply
  115. 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.

    Reply
    • Swag says

      Hello Ekoe, subscribing and downloading is not wrong for the publisher, but frequent downloading will increase your internet bill for sure

      Reply
  116. Lm324n says

    I made sg3525 inverter but one ouput of sg3525 is higher than the other output about 1 volt
    Is my ic fualty

    Reply
    • Swag says

      1V difference may not be a problem, but is it oscillating? confirm this with a frequency meter or with a headphone…

      Reply
      • thatcher says

        How to check oscillations with headphones?

        Reply
        • Swag 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

          Reply
  117. Lm324n says

    Can i use sg3524 instead of sg3525

    Reply
    • Swag says

      yes you can

      Reply
  118. Ekoe Anthony says

    Thanks Mr Swagatam for the quick response to my question on my modified inverter more grease to your elbows.

    Reply
    • Swag says

      You are welcome!

      Reply
  119. 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.

    Reply
    • Swag 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

      Reply
  120. 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?

    Reply
    • Swag 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

      Reply
      • 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?

        Reply
        • Swag 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

          Reply
          • 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.

            Reply
            • Swag 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?

            Reply
            • Swag says

              the waveform will be quiet similar to what is shown in the following article

              https://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.

  121. 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?

    Reply
    • Swag 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.

      Reply
      • 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?

        Reply
        • Swag 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://homemade-circuits.com/5kva-transformerless-inverter-circuit/

          Reply
  122. 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…

    Reply
    • Swag 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.

      Reply
  123. 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

    Reply
    • Swag says

      operate the oscillator stage through a 7805 or 7809 IC regulator…

      Reply
      • Dayo says

        I used 7812, is it bad . Thanks

        Reply
        • Swag says

          is it controlling the supply to the IC at 12V constant, throughout??

          Reply
          • Dayo says

            Yes, the supply is constant.

            Reply
            • Swag 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

          Reply
          • Swag says

            try 7809 IC

            Reply
          • Dayo says

            Sir, I have 7805, can I use it.

            Reply
  124. Solomon says

    How can i set the frequency of the circuit, or to calculate it?

    Reply
    • Swag says

      please check its datasheet for all the details..

      Reply
      • Solomon says

        Pls sir i need your help, so now fo this present circuit what is the frequency?

        Reply
        • Swag says

          Solomon, frequency should be set to 50Hz, and you can check this across the output pins of the SG3525 using a frequency meter

          Reply
  125. 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

    Reply
    • Swag 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://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.

      Reply
      • Solomon says

        Thanks. Sir, is there need for delay timer for an inverter?

        Reply
        • Swag says

          that depends on the user preference, it is not necessary.

          Reply
      • 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?

        Reply
        • Swag 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…..

          Reply
          • Solomon says

            Thank u sir, But is any problem if i connect the four MOSFETS together on 500w transformer and use 50AH Battery?

            Reply
            • Swag 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…

  126. 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

    Reply
    • Swag 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….

      Reply
      • 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

        Reply
        • Swag says

          You are welcome Solomon, the output waveform will be just as shown in the following article

          https://homemade-circuits.com/modified-sine-wave-inverter-circuit-2/

          Reply
          • 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

            Reply
            • Swag 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

  127. 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.

    Reply
    • Swag 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.

      Reply
  128. 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)

    Reply
    • Swag says

      Thanks Solomon, yes definitely you can add more mosfets in parallel for upgrading the capacity of the design….

      Reply
      • 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

        Reply
        • Swag says

          yes all the mosfets must have their own gate resistors, any value between 10 and 100 ohm will work

          Reply
  129. 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.

    Reply
    • Swag says

      Tolu, duty cycle should be 50%, so it is not an issue…you must check the voltage at the output…..

      Reply
      • Tolu says

        Good day sir, voltage is varied from 190-250v but still between 58-60%

        Reply
        • Tolu says

          Duty cycle is between 58-60%

          Reply
          • Swag says

            how are you measuring the duty cycle??

            Reply
          • Tolu says

            I use my multimeter

            Reply
            • Swag 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??

  130. 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

    Reply
    • Swag says

      chucks, such designs are already present in my website, please check the relay changeover category

      Reply
  131. kels says

    thank you for your good works!, can I use it for my sg3524 circuit

    Reply
    • Swag says

      thanks, yes you can use it…

      Reply
  132. 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

    Reply
    • Swag says

      solomon,

      you can replicate the arrangement which is shown in the following design, and use it directly with SG3525 circuit

      https://homemade-circuits.com/48-v-inverter-circuit/

      your second point cannot be feasible…

      Reply
      • solomon says

        ok, thank u sir, so now what will be the maximum power of the circuit

        Reply
        • Swag says

          Maximum power will solely depend on the wattage of the trafo and the battery AH rating…

          Reply
  133. 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.

    Reply
    • Swag 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??

      Reply
  134. 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…

    Reply
    • Swag 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://homemade-circuits.com/how-to-make-simple-200-va-homemade/

      Reply
  135. 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

    Reply
    • Swag 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

      Reply
  136. denmark says

    Sir good day, what is the value of transformer…

    Reply
    • Swag says

      you can choose any value as per your required specifications and battery specifications

      Reply
      • 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

        Reply
  137. 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

    Reply
    • Swag 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://homemade-circuits.com/48-v-inverter-circuit/

      Reply
      • 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?

        Reply
        • Swag says

          The capacitor is to smoothen the output waveform and make it more like a sinewave output

          Reply
          • Solomon says

            Sir, For the MOSFETs, can i use IRF540? or pls tell me a recommended MOSFET atleast two or three different types

            Reply
            • Swag says

              yes IRF540 will work!

  138. Solomon says

    Hello sir, where is pwm output for this circuit

    Reply
    • Swag says

      PWM is obtained from the IC 555 circuit or the opamp SPWM circuit.

      Reply
  139. 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.

    Reply
    • Swag 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

      Reply
  140. Dayo says

    When I measured the the frequency was not stable ranging from 120hz-260hz. Can it still work

    Reply
    • Swag says

      where did you measure the frequency? please provide proper details

      Reply
  141. Dayo says

    When I measured the down the frequency was not stable ranging from 120hz-260hz. Can it still work

    Reply
    • Swag says

      what is down frequency?

      Reply
  142. Dayo says

    Hello, is possible to measure the frequency of spwm and set before connecting to be bjt stage.

    Reply
    • Swag says

      yes, and that has to be done without fail…

      Reply
  143. 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

    Reply
    • Swag 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://homemade-circuits.com/mosfet-protection-basics-explained-is/

      Reply
  144. 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.

    Reply
    • Swag 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

      Reply
  145. Swag 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.

    Reply
    • Swag says

      you can use 3.3V also

      Reply
    • Swag says

      did you understand why the zener is being used, no point in trying randomly…

      Reply
  146. Swag says

    yes it will do…

    Reply
  147. tinuke says

    Please help me design a circuit for inverter voltage stabilization in reference to varying battery voltage and load variation. Thanks sir

    Reply
    • Swag says

      I think I have already referred you the circuit in one of the previous comments, anyway you can check it out here

      https://homemade-circuits.com/automatic-output-voltage-regulator/
      the output will be regulated only as long as it is not an overloaded

      Reply
  148. Swag 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

    Reply
  149. Swag 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.

    Reply
    • Swag 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???

      Reply
  150. tinuke says

    Hello sir, please between mosfet and igbt which one is better in efficiency and other features assuming they have same spec

    Reply
    • Swag says

      It is IGBT which has better efficiency than mosfet, if the load current requirement is high

      Reply
  151. 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 ?

    Reply
    • Swag says

      Hello Ekoe, except inductive loads or timer based loads, it wouldn’t have much effects on the load

      Reply
  152. 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.

    Reply
    • Swag says

      Hi, by closed loop do you mean an automatic load control through feedback? Please elaborate on this

      Reply
  153. Abhilash Sharma S says

    Sorry the frequecy of switching is 20 KHz

    Reply
  154. 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

    Reply
    • Swag 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://homemade-circuits.com/5kva-transformerless-inverter-circuit/

      Reply
  155. 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.

    Reply
    • Swag says

      Hi Reoc, it is not mentioned anywhere in the datasheet of the IC, still there’s no harm in trying it.

      Reply
  156. tinuke says

    Hello sir, please how can I minimize my modified wave inverter noise, everything working fine .thanks

    Reply
    • Swag 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://homemade-circuits.com/how-to-make-simplest-inverter-circuit/

      Reply
      • 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.

        Reply
        • Swag 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.

          Reply
        • 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.

          Reply
          • Swag 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.

            Reply
  157. 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.

    Reply
    • Swag 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.

      Reply
    • 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.

      Reply
      • Swag 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.

        Reply
  158. Reoc says

    Will the circuit work if the duty cycle of the secondary PWM is 50%?

    Reply
    • Swag says

      which secondary PWM?

      Reply
    • Reoc says

      I mean the PWM of 400Hz, I was asking if the system will work when the duty cycle is 50%.

      Reply
      • Swag 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.

        Reply
  159. 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?

    Reply
    • Swag 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.

      Reply
      • Swag 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.

        Reply
  160. 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.

    Reply
    • Swag 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

      Reply
    • 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.

      Reply
      • Swag 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.

        Reply
      • 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?

        Reply
        • Swag 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.

          Reply
        • 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?

          Reply
          • Swag 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

            Reply
          • 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?

            Reply
            • Swag 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

            • Swag says

              please see the last diagram from this article, you can configure the transistors in this manner

              https://homemade-circuits.com/2013/10/making-3kva-modified-sine-wave-inverter.html

            • Swag says

              but in the particular configuration as given in the linked diagram, TIP36 is used which is a PNP

  161. 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 .

    Reply
    • Swag says

      current consumption will depend on load specs not on inverter specs

      Reply