4047 sine wave inverter circuit - Pure Sine Wave Inverter Circuit Using IC 4047

Pure Sine Wave Inverter Circuit Using IC 4047

A very effective pure sine wave inverter circuit can be made using the IC 4047 and a couple IC 555 together with a few other passive components. Let's learn the details below.

The Circuit Concept

In the previous post we discussed the main specifications and datasheet of the IC 4047 where we learned how the IC could be configured into a simple inverter circuit without involving any external oscillator circuit.

In this article we carry on the design a little ahead and learn how it can be enhanced into a pure sine wave inverter circuit using a couple of additional ICs 555 along with the existing IC 4047.

The IC 4047 section remains basically the same and is configured in its normal free running multivibrator mode with its output extended with the mosfet/transformer stage for the required 12V to the AC mains conversion.

How the IC 4047 Functions

The IC 4047 generates the usual square waves to the connected mosfets creating a mains output at the secondary of the transformer which is also in the form of square wave AC.

The integration of the two 555 IC to the above stage completely transforms the output into a pure sine wave AC. The following explanation reveals the secret behind the IC555 functioning for the above.

Referring to the below shown IC 4047 pure sine wave inverer circuit (designed by me), we can see two identical IC 555 stages, wherein the left section functions as a current controlled sawtooth generator while the right hand side section as a current controlled PWM generator.

The triggering of both the 555 ICs are derived from the oscillator output readily available across pin#13 of IC 4047. This frequency would be 100Hz if the inverter is intended for 50Hz operations, and 120Hz for 60Hz applications.

Using IC 555 for the PWM Generation

The left 555 section generates a constant sawtooth wave across its capacitor which is fed to the modulating input of the IC2 555 where this sawtooth signal is compared with the high frequency signal from pin3 of IC1 555 creating the required pure sine wave equivalent PWM at pin#3 of  555 IC2.

The above PWM is directly applied to the gates of the mosfets. so that the square pulses here generated through pin10/11 of IC4047 gets chopped and "carved" as per the applied PWMs.

The resulting output to the transformer also causes a pure sine wave to be stepped up at the mains AC secondary output of the transformer.

The formula for calculating R1, C1 is given in this article which also tells us about the pinout details of the IC 4047

For the NE555 stage C may be selected near 1uF and R as 1K.


4047 sine wave inverter circuit 1 - Pure Sine Wave Inverter Circuit Using IC 4047



Assumed output waveform

sine waveform 1 - Pure Sine Wave Inverter Circuit Using IC 4047

An RMS adjustment could be added to the above design by introducing a pot voltage divider network across pin5 and the triangle source input, as shown below, the design also includes buffer transistors for improving mosfet behavior


4047rmsadjust 1 - Pure Sine Wave Inverter Circuit Using IC 4047


The above pure sine wave inverter design was successfully tested by Mr. Arun Dev, who is one of the avid readers of this blog and an intense electronic hobbyist. The following images sent by him prove his efforts for the same.


4047 inverter 2 - Pure Sine Wave Inverter Circuit Using IC 4047
mosfet stage inverter 1 - Pure Sine Wave Inverter Circuit Using IC 4047

transformer connected to load inverter 1 - Pure Sine Wave Inverter Circuit Using IC 4047
load activated inverter working 1 - Pure Sine Wave Inverter Circuit Using IC 4047

BJT stage added to inverter 1024x576 1 - Pure Sine Wave Inverter Circuit Using IC 4047


pwm stage of the inverter 1 - Pure Sine Wave Inverter Circuit Using IC 4047

load after pwm 1 - Pure Sine Wave Inverter Circuit Using IC 4047


Inspiring response received from Mr. Arun regarding the above IC 4047 inverter results:

After completing this circuit, the result was amazing... I got full wattage by the 100 W bulb..... Couldn't even believe my eyes.

The only difference i had made in this design was replacing the 180 K in the second 555 with a 220 K pot to adjust the frequencies accurately....

This time the result was fruitful in all respects... On adjusting the pot, i could get a non disturbing non flickering full wattage glow in the bulb, also the 230/15 V transformer connected as the load gave a frequency in between 50 and 60 ( say 52 Hz )....

The pot was adjusted gently to get a high frequency ( say 2 Khz ) output from pin#3 of second ic 555... The CD4047 section better calibrated to get 52 Hz at the two output terminals....

Also i am facing a simple problem... I have used IRF3205 mosfets at the output stage.... i forgot to connect the safety diodes across the drain terminals of each mosfets...

So when i had tried connecting an another load ( say table fan ) in parallel to the given load ( 100 W bulb ), the glow of the bulb also the speed of the fan were got reduced a little and one of the MOSFET was blown due to the absence of the diode....

The above 4047 sine wave inverter circuit was also tried successfully by Mr. Daniel Adusie (biannz), who is a regular visitor of this blog, and a hardworking electronic enthusiast. Here are the images sent by him verifying the results:

Sawtooth Waveform Oscilloscope Output


triangle wave 1 - Pure Sine Wave Inverter Circuit Using IC 4047


test set up 1 - Pure Sine Wave Inverter Circuit Using IC 4047


Illuminating a 100 Watt Test Bulb


4047 inverter 1 1 - Pure Sine Wave Inverter Circuit Using IC 4047


The following images show the modified waveforms at the output of the transformer as captured by Mr. Daniel Adusie after connecting a 0.22uF/400V capacitor and a suitable load.

The waveforms are somewhat trapezoidal and are far better than a square wave which clearly shows the impressive effects of the PWM processing created by the IC555 stages.

The waveforms could be probably even further smoothened by adding an inductor along with the capacitor.

Showing an near Sinewave Oscilloscope Trace  after PWM Filtration


IMG158 1 - Pure Sine Wave Inverter Circuit Using IC 4047


IMG161 1 - Pure Sine Wave Inverter Circuit Using IC 4047


IMG163 1 - Pure Sine Wave Inverter Circuit Using IC 4047

For connecting more mosfets in parallel (to increase wattage), the PWM integration could be made at pin9 of the IC 4047 for achieving the same. The connection details are shown in the following diagram:



4047 pwm inverter circuit 1 - Pure Sine Wave Inverter Circuit Using IC 4047

Intersting feedback received from Mr. Johnson Isaac who is one of the dedicated readers of this blog:

Good day
In your post, Pure Sine Wave Inverter using 4047, in the second I.c stage (ic.1) you used 100 ohms resistor in between pin 7 and 6.,
Is that correct? I use to think an astable multivibrator using 555 pin configuration should have the 100 ohms between pin 7 and 6. Also, the 180k variable between pin 8(+) and pin 7. Pls check the pin connection and correct me pls. Because it oscillate sometimes and it doesn't sometimes also. Thanks,
Isaac Johnson

Solving the Circuit Issue:

In my opinion, for a better response you can try connecting an additional 1k resistor across the 100 ohm outer end and pin6/2 of IC1


Thank you very much for your response. I actually constructed the inverter you gave in your blog and it worked.

Though I don't have an oscilloscope to observe the output waveform BUT I bet readers its a good one cos it operated a fluorescent tube lamp in which any modified or pwm inverter can't power on.

See the picture sir. But my challenge now is when I add load, the output flickers sometimes. But am happy its a sine wave.


IMAG0209 1 - Pure Sine Wave Inverter Circuit Using IC 4047
IMAG0207 1 - Pure Sine Wave Inverter Circuit Using IC 4047

468 thoughts on “Pure Sine Wave Inverter Circuit Using IC 4047

  1. Have questions? Please feel free to post them through comments! Comments will be moderated and solved ASAP.
  2. Dear Sir,
    Thank you for a nice and simple schematic.
    By the way what are the values of capacitors which are
    connected to pin 1 of both 555 IC's ? You mentioned them as
    C and C only.

    Thank You.

    • Hi Swagatam
      I just want to clarify something on the above circuit.
      If the IC 4047 oscillates at 100hz then there will be 50 + positive half cycles so the IC 555's which oscillate at 100hz will chop each + half cycle just once.
      I thought you need 50*100 chops in one cycle for effective PWM
      Regards Robin

  3. hello mr swagatam i really have to confess to you, since i've come accross this site i've been addicted to it, thanks for being a mentor and also a teacher to me, i realy appriciate the good work and effort you've put toward educating people like me thanks once again.

  4. hello Mr Swagatam I have been following a lot of ur other circuits and built a few so far. How could u incorperate a output voltage correction circuit in this design because i know that with varing loads we will get a voltage drop here. Thank u for ur support

    • hello Alex, it can be done by adding a opto couper circuit across pin#5 of the right hand side 555 IC, quite similarly to the method discussed in one of my previous posts.

    • ok thank u Mr Swagatam I am going to build this circuit until Mr Robin comes up with the report on the other design with the 4017 I really want to get one of these circuit s going Sir. Thank u for ur support to us

    • hello Mr swagatam i am trying to understand ur principles every day more and more. Please tell me if I have it wrong . Lookin g at this circuit is it possible to use sg3524 in place of the 4047 and send pin 3 which is the oscilator out from the sg3524 and feed the two 555 ic just the same way as how u send the pin 13 of the 4047 to these two ic.. Would we get the sine wave effect with this ic.Thank u Sir just want to know if I am learning or I am wrong on the principle

    • thank u Mr Swagatam I want to make sure I am unerstanding the principle because sine wave inverter circuits are so hard to find online and every body discourage us from building them but u make it look so simple in ur designs well I think the filtering part might be the hard part. Still waiting on Mr Robin to come back to us witht the finish product of ur 4017 sine inverter. Thank u Sir

    • hello Mr Swagatam I seee u have changed the above circuit by adding another 555 should we build it this way now instead of the first circuit . could u explain this new addition . Thank u Sir

    • Yes, we need to build it in this way. The chopping pulses needed to be of much higher frequency than the triangle pulses, that's exactly what's been modified in the new design.

    • ok thank u Mr Swagatam I built the top section lastnight with the 4047 and that section works only that I cant really set the output voltage to the exact amount i need because ther is no control pot for this >. Monday I will build the other section and tell u the result Thank u Sir

    • Thank u Mr Swagatam for ur help I am getting the parts together to build. I hear they talk about efficiency of sine wave inverters being difficult to achieve thats why we should buy instead of building what is the efficiency of this inverter and would we need a filter after the transformer . If we need a filter could u add for us please. Thank u Sir

    • Mr Swagatam I built this circuit but I am having problems with it . The section with the 4047 works I get my ac voltage out ok . When ever i connect the bottom section ( the two diodes to the gates the circuit shuts down and no ac commes out..I even loose the drive signal from the 4047. I dont have a scope so it is difficult to show u any wave form. All I can say is I am getting about 91Hz from pin 6&7 junction with the collector junctuon from the left ic that signal that goes to right ic pin 5. I get about 552hz from pin 3 of the middle ic and about the same from the right ic pin 3 just dont know wher to go from here. So as long as i lift the gate drive from pin 3 of right ic the circuit comes on again. Please help me here Sir. Thank u

    • Mr Alex, Where did you hear this? Please show me any link where this is discussed.
      Modified sine wave inverters are actually controlled square wave inverters, so they are as good as a square wave inverter.

    • Please check the following things in your inverter design:

      Check frequencies at pin5 and pin2 of IC2 (extreme right 555)

      Pin5 should show = 100Hz approx
      Pin2 = high frequency…2kHz will be OK, adjust 180k resistor for this.

      The voltage at pin5 and pin3 of the above IC should be approximately equal.

  5. hello Mr Swagatam I had a try at the circuit again but had some problems. I got the 100 hz at pin 5 2khz at pin 2 . The 4047 section as a inverter works but as soon as i connect the diodes to the gates the output voltage just comes up to about 20v and goes right down immediately dont know if something is wrong with the circuit diagram. please help us here Sir.

    • Alex, check the output voltage at pin3 of IC2 555, it should be around 30 to 50% of the the battery voltage meaning around 3 to 5V.

      Connecting the diode to bases of the mosfets will drop the output voltage but not to 20V that's too low.

      please check and tell me about the above readings.

    • ok Mr Swagatam I think I will give this circuit a break for now and start to build the other circuit that Mr Robin is persuing in that his own seem to working to a certain stage sir I will let u know the results

  6. maybe the square wave signal at the gates of the 4047 gets attenuated when the diodes are applied so we may need to buffer it or something.micheal

  7. may be because the triangle wave peak is not equal to supply voltage, it's only 2/3rd of supply.
    pls could you expalin the above statement? thanks

  8. Sir,
    Prior doing this project i had just tested the working of a simple inverter using IC Cd4047 as given in this link


    But it got failed. The problem is that when i am connecting the center tap of the power transformer to the battery positive a spark appears and battery charge goes down to zero voltage and no ac output.

    I am using a 300 W 15V power transformer with 5 primary taps and 4 secondary taps. The 15-0-15 voltage has been taken by
    1st and 4th tap wires being +15V and -15V respectively and the 2nd and 3rd wires rapped together to avail 0v. The battery being used is a 12V 20 Ah battery

    i have also tried with taps 1-3-4 and 1-2-4. But the same problem persists. So will you please help me in solving this issue.

    Is there anything wrong with my transformer …. I have used the high power transformer and the battery without considering their specification, my only aim was to test whether the inverter functions properly, and then only proceeding to further high power design

  9. Forgot to say sir. I have used IRF540N instead of IRF150 in the circuit. Also there is a slight change in the value of C1 and C2 used. I have used a 0.1 uf ceramic capacitor at the oscillating circuitry of the IC CD4047. Resistance R1 used is 22.7 K (adjusted by a potentiometer ). These values were obtained by solving the formula
    f at 10th and 11th pin = 1/(8.8RC) for 50 Hz at pin 10 and 11.
    Instead of 0.1 uf/600V b/w the secondary terminals, i have used a 1uF/450V Electrolytic capacitor.

    So i want to know whether does these changes cause that problem….

    • The issue is no doubt with your circuit connections, either you have connected the mosfes wrongly or the transformer taps.

      Try an ordinary small 12-0-12/220V transformer with your circuit and confirm whether your circuit connections and working are OK or not.

      Once your circuit working is confirmed, next you can connect different taps of your actual trafo for the intended correct results.
      Connect a 12V car headlight lamp in series with your battery positive…this will restrict any possible short circuit hazard and blowing of mosfets.

  10. Sir please help me in identifying the connection of an optocoupler to this stage for automatic load correction. I found one in your previous article, but there optocoupler's +ve terminal is connected to the RMS voltage. I can't distinguish that from this situation.
    Also can you add a selectable overload protection circuit in this schematic. Even an overload indicator is enough for me

    • Ram, no buffer stage is required accordion tome…..i would advise you to first successfully build the above shown inverter, once its working is confirmed we can go ahead with the opto stage.

  11. I am not getting 3 to 5 volts at pin#5 of IC2. Only 2.72 V
    Also pin#3 voltage is 2.5V seen that is not equal to that at pin#5. What to do
    Is this circuit a tested one???? ALSO TELL ME HOW TO MEASURE FREQUENCY AT RESPECTIVE PINS USING A DIGITAL MULTIMETER. I can see a square wave symbol in the meter, but don't know how to connecte the leads to measure hertz

    • Did you study and understand the complete functioning of this inverter before building it?

      The above circuit is a complex design and is only meant for experts hobbyists.

      I would suggest you to first learn all the basics of inverter and then go for the practicals.

      You should first try building a simple inverter.

  12. Sir what does it means 'D1 2V7'
    Is it a zener diode????

    Can i use a 4V7 zener. In my earlier doubt, i had forgot to say you that i have used a 4V7 zener in this place

    • 4.7V zener will also work, don't bother about the lower 555 circuit, remove the stage and check only the 4047 inverter first.
      If it works only then attach the 555 circuit with it.

      you are getting 2.7V at pin5 and 2.5V at pin3 which are almost equal, so may be your circuit is working correctly.

      remember your trafo voltage should be 50% of the battery voltage,means if battery 12V use a trafo rated at 6-0-6V

    • Hello brother nice work. I always appreciate your posts. Kindly help me with one thing that's confusing me. I am using IRF3205 power mosfet. As i am understanding just two irf3205 can deliver 600W power. What do you say? and also what if i use 4 irf3205 to have the same power on the same transformer which is 220v-500Watt
      Waiting to hear from you.

    • Hello Xaidi, thanks!
      yes if the mosfets are adequately cooled then it could be used for switchng that much power.

      the transformer is the actual power source, while the mosfets are just power switches, therefore the output will finally depend on how much the transformer is able to produce, the mosfets are only responsible for switching or carrying this power, so it will have no role in developing or enhancing the output power….

  13. Sir can i use a battery of the order of below 100 Ah such as 50 or 60 Ah with a 300 W transformer intended to produce the required wattage only ( less than the rating of the transformer ). ????…..
    When i am connecting a single 20 Ah battery to the simple inverter using only IC CD4047 i am getting ac out, but when 3 or 4 batteries are connected in parallel no ac output……. when ac is present there is a humming noise produced by the transformer……. I have used the parallel connection schematics as explained by one of your earlier posts in which diodes are used

    • yes you can use lower rated batteries for operating the rafo with lower watage
      check the voltage of your batteries when connected in parallel, the diodes mus be rated for carrying over 10amps, use two 6A4 diodes in parallel…..or may be you can try them without the diodes too, if all are above 12.5V

  14. Sir a 6-0-6 power transformer is not with me. Can i use the 10-0-10 tap of the one already have. What happened if 12 V tap is used.?????
    Sir by measuring frequency in ac socket ( putting negative lead to N and positive to P aftet setting ti frequency range ) i got a value near 150 . Is it correct???? Actually should it be 50??'?
    Sorry 4 the bad english

  15. Sir as you suggested at the last time, i have tested the single inverter circiit using only IC4047. At first time i got some ac output, but after sometimes nothing came out through transformer secondary. I saw a reduce in battery voltage when it had connected to the 0 tap. I am using a power transformer rated 20 to 25 A at secondary and batteriea are rated 20 AH 12V each* 3 no.s.
    This time i didn't use any dioded for the parallel connection. But the result was the same with diodes. Please help me

    • 12-0-12 trafo will be OK if you are not incorporating the lower PWM stage, if you want to include the pwm stage then a lower voltage trafo becomes essential.
      You might have blown off the mosfets, or the IC, or your battery could be dead.
      You can try using transistors instead of mosfets as they are easier to handle. you may take the help of this article to know how to connect the transistors:


      connect 12v head lamps to your battery and check their intensity to confirm the battery condition, and for the inverter circuit use only one battery initially instead of using all the batteries together.

  16. sir its this circuit a pure sine wave Pure Sine Wave Inverter Circuit Using IC 4047 and also what is the different between ne555 and (7)555 can i use ne555 for all the three ics? can irf540n be ok without problem?thank you sir i am waiting for your reply.

  17. Sir i found the modification done to this circuit by Mr. Robin at earlier times as in the figure given in the following link.


    I tried your basic circuit as well as this modified one. But the results were not fruitful and remained the same providing an ac output of around 20 V only.
    Please read what changes i had done to this…..
    Since i do not have an oscilloscope with me i was unable to make out an exact 2Khz by the first 555 in the modified version. But i have a simple digital frequency meter with me. So i could confirm the frequency of the last 555 ( which gives clock pulses to 4017 ) out to be exactly equals 200 Hz. I thought this 555 stage is a 50% duty cycle pulse generator ( since it employs diodes ) and the resistances 1 K and 3.4 K were replaced by 470 ohm and 10 K respectively and tweaked the 10 K pot to make the output wave form exactly equals to 200 Hz. After confirming this step I HAD USED THE SAME 555 STAGE to generate 2 Khz signal, but this time 0.05 uf capacitor was replaced by 0.5 uf one ( because of the formula for frequency of 50% duty cycle wave as f=1/(0.69RC) )
    Now it is expected to produce a 2 Khz signal by the first two 555 ics. I have also made a change that 4047 was used instead of 4017 and the pulses from 3rd 555 stage were fed to pin#13 ( CLK INPUT ) of it. No more changes to say

    Now i have some doubts…

    1). The voltage at gate of each mosfet w.r.to ground had reduced to 1.3 V compared to the simple configuration in which no pwm section were used ( 5.6 V ). How to solve this issue sir ? thereby i am getting very low ac output
    2). Will the frequency of pulses fed to the gates be 50 Hz even after feding the pwm stage ? ( i am getting higher values compared to the simple configuration not using pwm in which 50 Hz was shown )
    3). How to use the 10 K pot in the 2nd 555 stage in the modified version ?
    4). I have found a more better circuit provided by Mr. Theofanakis at the last page of that article given in this link


    Will it be more effective and can be used for even sophisticated applications ?

    I am expecting your reply as soon as possible sir

  18. Thank you very much sir for replying.
    I will inform you any changes ,will occur doing further verification of the entire circuit.
    What is the part no. of the optocoupler being used with an LED for output voltage regulation in the picture given in the link you provided ? Can i make the combination manually. How it can be done ?

  19. sir in this circuit i want to ask you that in the 4047ic can i use (10k for R1) (10k for p1) (0.01uf for c1)?
    sir please answer this question for me in fact in my country we don't have this kind of ic (7)555 i never seeing this ic before only we know or we have here is ne555 so can it be use in place of the two ic (7)555 ca i can see the left side of the hand is ne555

    • biannz, try googling "4047 inverter circuit"…you will come across many designs online where you will be able to get the exact values of P1 and R1

      NE555 will also work

  20. sir please it D1 a zener diode 2.7v?,sir please i have check 4047 on Google and a lot of them but sir there something i don't understand please explain it for me the 4047 it produce square wave so how come this inverter be produce pure sine?
    the 555 stage need to be power? thank you sir.

    • sir in my circuit i,m having 50.79hz in both pin 10 and 11 and 101hz pin 2 of ne555, 426hz in pin 2 of ic2 and 101hz at pin 5 of ic 2

      pleas sir is 180k rsesis a pot? and which of the is responsible for the 2khz and also i use ne555 for the 3 because 7555 is not avalaible. please what could be wrong with my circuit

    • faith, 180k is a fixed resistor. it's neither a pot nor a preset.

      your readings look quite OK to me.

      2kHz is not important…you can carry with your present set up.

      the 426hz becomes the carrier frequency, and the 101 Hz becomes the modulating frequency for the PWM…that looks fine to me.

  21. ok sir i have sent you the pic sir please try to help me build this circuit even if i survive building this circuit i will not go for any other inverter circuit i hope this circuit is good enough for me if you help me, sir please im appealing to you if it could be possible for you to send me the prototype if you have a time to design it thank you hope to hear from you.homemadecircuits@gmail.com

    • as expected you have only simulated the design and have not tested it by building it practically.

      pls don't discuss simulated results with me.

      procure the components, build it practically and only then confirm the results with me.

    • remove the 1N1448 connection temporarily from the mosfet gates and check whether the 4047 inverter is working normally or not.
      It should, if it doesn't means your IC or connections are bad.

      If it shows normal response, check the following things in the 555 section:

      frequencies at pin2 and pin5 of IC2 and also the respective voltages at these points, tell me the results, i'll instruct you with further procedures.

  22. ok sir thank you for your kindness im quite appreciate,sir i did as you said when i got 5v at pin5 of ic 2,when i remove the tow 1n4148 diode the circuit work so i got 152ac out put but there is some noise from the circuit i have sent you the video so please check it for sir why the noise? sir what is the per pose of the two 1n4148 diode and can this circuit be use without two 1n4148 diode?.

    • biannz, use 6-0-6 trafo if the battery is 12V, this will give 220V approximately even with the diodes connected.

      you get pwm sinewaves only when the diodes are connected otherwise it's just square wave.

      the diodes shape the mosfet gate triggers into digital sinewaves.

      I am not so sure about the noise, it will be there somehow, try clamping the trafo hard.

  23. sir please i checked all over the circuit everything is connected as it showed i didn't make any mistake sir the problem is the two diode if removed it work but if i connect it doesn't,sir pls is there any way to change the direction of the two 1n4148 diode? i used 6-0-6v transformer but not seem to work sir.

    • check the voltage at pin3 of IC2, it should be around 50% less than the battery voltage,

      the lower 555 stage is creating the pwm waves which is fed via the diodes to chop the mosfet gate voltage causing them to conduct according to the pwms, thus forcing them to generate the sine waves over the trfo.

      your 555 stage may be faulty or with tecnical issues.

  24. sir please in this circuit
    300 Watts PWM Controlled, Pure Sine Wave Inverter Circuit with Output Voltage Correction you design it two times which one is correct and can be use? you detected ic1 ne555 and bd135 so which one it should be contracted?

    sir please answer this two question thank you.

    sir i have sent you a video and the circuit,i build it i got 4.8 frequency going it don't stable and i got 223AC at out put so sir can you please help me cos i don't think this can handle a load i put 220v AC fan but it couldn't

  25. sir thank you.sir please tak a very look at this circuit for me the second circuit you said it is implemented by the inclusion of the LED/LDR opto-coupler stage. i build it it work so sir please should i set the frequency at the out put of tranf or at the pins of the ICS as you shown 180k preset? 300 Watts PWM Controlled, Pure Sine Wave Inverter Circuit with Output Voltage Correction

    sir pls can i you IRF1404 in place of IRF540N?
    sir it this circuit a pure sine wave?
    can this circuit be build up to 5kv 5000W?
    can 4n35 be replace the led and LDR?
    it s possible to use 24v DC? thank you sir i will be happy if you answer all this questions one by one for me to understand it well

    • biannz,

      LDR/LeD module is NOT for adjusting frequency, it's for adjusting the output voltage.
      for frequency setting, do it by adjusting the IC1 preset.

      check the datasheet of the mosfet, if it's wattage is beyond the desired load wattage, the you may use it.

      first make it to handle 200 watts correctly then we can proceed for higher loads

      only LDR will work, nothing else can be used.

      24v can be used, but use 7812 for supplying the ICs, else the ICs will fry at 24V

  26. Sir,
    Eventhough i am working in musical industry ( Music production ), i am a big enthusiastic of making such small small electronic projects…. I am used to go through almost every projects you posted in this blog…. So i have noticed the making of that optocoupler also.. That automatic output voltage regulator, i have also noticed… I am very much confident in building even complicated designs myself using the basic knowledges in electronics, i had achieved in my whole life…. But to complete and make the undertaken project working, valuable helps and suggestions from experts like you are necessary…

    So could you plz tell me sir, to which point in this circuit, i should have to connect the optocoupler for solving the output voltage regulated issue ??

  27. Sir, if i am doing so will there be any confusion arised to IC2 stage in comparing the signal arrived at its pin#5 with the high frequency signal ( say 2 Khz ) arriving at its pin #2.
    Because, there is already a sawtooth / triangular wave reaching pin#5 from its generator.. So if i am incorporating the additional optocoupler stage, there is also an another signal to pin#5 from this… So how would that comparison be look like, means how the IC2 stage is gonna efficiently handle this situation without changing the sine wave nature of the inverter also incorporating output voltage correction feature.

    I am also having another doubt,
    Can any high frequency be used to compare in the IC2 stage ? Any problem with 2 Khz wave ?

  28. Sir you mean, connecting the diodes( 1N4148 ) of the output voltage regulator to the gates of the MOSFETS ?
    Two diodes are already connected to those terminals for sine wave operation, reducing the voltage at those terminals from 5.9 volts to around 3.0 V…. So if we are gonna connect the diodes in the regulator section again in the same place, will that voltage be reduced again to a small value so that the MOSFETs will be unable to conduct ???

    As i have noticed from the design that the gate voltage when the PWM stage connected was only 3.0 V, Is that possible to think for a single transistor amplifier or anything like that to boost this voltage for maximum power output ?

    • Arun, yes that's right, connect the diodes from the regulator circuit too at the gates of the mosfets.
      these diodes will only conduct when the output is above normal, otherwise they would be inactive.
      PWM is introduced to carve the voltage as per the duty cycles of the pwms, so the voltage will reduce….but 3V is the average voltage that you are seeing, the peak voltage of the gate pulses will be always equal to IC supply voltage…measure the peak by using a suitable digital meter set at "peak" or "MAX" voltage at the gates.

      it's your wish, if you want to use BJT stages you can do so.

  29. Sir Now i got exactly what those digital meter readings say exactly at gate terminals… I could found the actual peak to peak voltage by the method you suggested last time ( taking voltage across a 10 uf capacitor……… )…… THANKS FOR GUIDING ME THROUGH THE RIGHT PATH….

    As i said before the voltage at the gate terminal reduces from average 6.0 V ( 12 V pp ) to average 2.8 V ( approx. 5.8 Vpp), reducing the power considerably….. But when i am connecting transistor amplifier stage before each gate terminal, voltage retains the peak level ( 5.8 V average ) and the power increases as in the case without PWM….. On checking the frequency at the gate terminals ( collector terminal of transistor ) i got only 52 Hz, but it was found to be 520 HZ something at the transistor base terminal, so actually functions as the stage without PWM…… So i have some doubts..

    1). What z the reason for this mismatch ?

    2). How to make use of these transistor amplifier stage efficiently to avail full voltage at each
    gate terminal with PWM connected, producing maximum power output ?

    2). What is the reason, in the original situation ( without the use of any transistor amplifier
    stages ) behind the considerable reduction in voltage in gate terminals ?

    I could understand, by reading your last comment, that the output voltage will reduce considerably if a 1 uf capacitor is used at that terminal and the battery will drain quickly. And also found the circuit you have suggested that could compensate for higher value capacitors being used in co-operation with inductors… So

    3). Can you suggest me a method by which any valued inductor can be made by hand ?….. I
    have copper wires with me

    • Arun, I think still you haven't understood the utility of the PWM stage

      PWM is introduced to chop and reduce the final RMS so that it matches with the real sine AC RMS approximately.

      A lower voltage transformer is intentionally used to counter this drop so that it can be raised to the desired levels by the trafo.

      You cannot get 5.8V, the peak voltages from the IC will be always equal to the battery voltage under any case.

      As far as the inductor is concerned I have no idea about the calculations, it could be quite complex.

      By the way in your transistor amp where did you insert the PWM diodes?

    • you will need an oscilloscope for measuring the actual frequency, your meter will give wrong results due to the high PWM frequency insertion over the basic 50 Hz.

  30. I have introduced the transistor amplifier before the gate terminal, and the PWM diodes are connected to the base terminal of the transistor ( using a 10 K resistor ) along with the resistance from output terminal of IC4047….. ( i have send the image to your mail…. Plz check it out )….. Then output of the transistor ( collector ) is then directly connected to gate terminal….
    Sir, my frequency meter could show high frequency waves at gate terminals ( say 520 Hz under PWM ) keeping the transistor amplifier disconnected… It could also show 52 Hz when PWM stage disconnected…..

    The noticed thing is : when the frequency is checked at the collector terminal of the transistor without pwm, it was the same 52 Hz…. But when it is checked again under PWM ( 520 Hz seen at the base ), it shows the same 52 Hz reading……….

    • if you have connected the diodes directly with the BJT bases then it would work normally as before.

      The frequency will be 50 Hz at the trafo output but the meter will not be able to pick it up due to harmonic content.

      I have update the RMS control circuit above, you can check it out.

  31. Let me try to do the updation Sir.. I would let you know the results soon….

    But what z about the reduction in voltage at gate terminals when PWM stage came to act ( without using any transistor amplifier stages ) ? Any solution for it, to maintain full voltage at the gate terminal, at any conditions ??

    • the peak voltage from the IC outputs and at the mosfet gates will be always equal to the supply voltage that's applied at the Vdd of the IC.

      THe transistor stage that you have used serves no purpose.

      PWMs are made up of high pulses and zero pulses, during high pulses the diodes are completely blocking them, meaning during these periods the gates must be getting the full IC output voltage, how can the peak voltage drop then??

      Only during the zero pulses from the PWMs, the gates are forced to become zero (grounded) through the diodes.

      The oscilloscope images in the previously referred article by Robin peters clearly show this effect

  32. hi sir it been a while sir you have renew this circuit sir please what is the purpose of the 10kpots? sir please can you tell me the value of c and r with bc557 thank you.

    • Hi bianzz, the 10k preset or pot may be used for trimming the output voltage to the correct level. For example if suppose you are getting 300V initially, you can adjust the 10k pot until the outputs settles down to 220V, conversely if initially the output shows a lower level such as 180V, the same may be used for pulling it up to 220V

  33. I forgot to ask you an another doubt :

    In your last comment you said this,
    " if you have connected the diodes directly with the BJT bases then it would work normally as before. "
    So you mean, if i am gonna use Transistor amplifier section, it will only function like that stage without PWM feature ( Only Square wave AC output ) ???

    • procure a multimeter which has a peak voltage detector or a MAX voltage detector option, the feature will enable you to see the max voltage at any point….. and the meter will also lock the result for proper reference.

    • or it would be even better if you could go back to basics and learn how CMOS outputs behave and what the 555 PWMs are made up of and how they work.

  34. ok sir thank you sir plse in the 4047 i build this circuit but the problem is i got 4.7v at pin 10 and 4.9v at pin 11,sir pin11 going to the fets gate got very hot it almost burn

  35. ok sir i got it right now the circuit is ok but sir what nest for me to do to make it handle heavy load?i put 220 fan it work but the speed is very low and put 60w bulb it lit up well i have sent you the pic of it to this email address homemadecircuits@gmail.com including the wave form of it check it for me if the wave form is ok it is a trangular wave form or pure sine equivalent?

    • thanks Biannz, I saw the images, where did you check those waveforms if it's at pin5 of IC2 then it's fine, if it's at the output of the transformer then it's NOT fine…the output will not generate triangular waves rather an approximate sine wave…..connect a 0.22uF/400V capacitor across the output of the trafo and check again.

  36. ok sir the wave form is at of ic2 pin 5, i forgot to test transf out put i well test it and send it to you, it very difficult to get 0.22uf/400v cap here only we have is 0.22uf/27v but still the fan could not speed up and there is much noise in the fan when it working thank you.

  37. Sir are these reading OK ?

    1). Frequency generated by IC1 pin#3 and fed to IC2 = about 2.2 Khz

    2). Frequency generated by CD4047 ( at pin#13 ) = 106 Hz corresponding to two 52 Hz opposite phased square waves at pin#10 and #11.

    3). Frequency of the sawtooth wave form from leftmost 555 IC = 106 Hz

    4). Frequency output ( across pin#5 capacitor ) of IC2 = 106 Hz, which is the PWM signal

    Comparing the High frequency ( say 2.2 Khz ) with the sawtooth frequency ( 106 Hz ) i am getting the low frequency ( 106 Hz ) value as the PWM frequency…

  38. 1).Sir If i am not using a PWM stage , What is the real wave form fed to each secondary windings of the transformer other than the null tap ?
    Is it a quasi square wave or just a square wave ?

    2). Sir if i am using the PWM stage, will the shape of the wave get affected ?

    3). Does the wave fed to each winding has -ve and +ve cycles or just a half cycle ?

    Could u plz check your hitman inbox ?

    • Arun, without PWM it will produce square wave without RMS control

      2) with PWM on, the shape of the wave cab be controlled to match sine wave RMS and properties.

      3) yes the winding switch alternately in opposite directions resulting in +/- cycles at the output.

  39. At last by many trial and errors, without using any DSO, i got the maximum power output at the output terminal of the inverter..
    But the circuit in which i made success is not this one. That is the PWM controlled 300 W pure sine wave inverter which you had posted in your blog earlier…


    On inspecting this circuit at initial stages, i got gate voltages equal to about 3.0 V ( Average ) only… I have tried many methods to amplify this signal to at least 6.0V to make the MOSFETs conduct to enable maximum power output, as i have told you many times. But all of them failed, have also told you about this.
    At last i have studied the pin details of IC4017 in detail and carried out different practical tests on it… Then i could understand that,
    the output voltage available from each output pin of CD4017 = 12V * Duty Cycle of the wave
    So if i am connecting pin#10 ( corresponding to 25 % duty cycle ) to the reset pin ( Pin #15 ), i will get only a peak to peak voltage of 6 V.. From this, it is clear that seeing 3.0 V average at the output pins of the IC ( pin#2 and #7 )

    So i have changed this connection and connected pin#4 ( by trial and error ) to pin #15. Now i got 6.0 V average at the consecutive pins pin#2 and #3.. But the earlier 52 Hz frequency has been increased to a higher value say ( 150 Hz something )….so frequency adjustment was done at the 555 stage which feeds the clock signals to the IC.. the feeding frequency was adjusted to 100 Hz…then i got exact 50 Hz signals at the above stated pins…. The voltage was 6.0 V average on both pins…. Next step was to ensure whether the signals at these pins are appearing in tandem….I have confirmed this by placing two LEDs at these terminals at 1 Hz frequency……. So everything was set up….
    Praying the god, connected the transformer and fired the center tap using the 24 V source…… The result was awesome… Full power output at the inverter output…. No such considerable harmonic disturbances were detected.. Only a slight squeezing sound was heard… Then i have connected the PWM stage…. As in the case of the CD4047 inverter in this page, the gate terminal voltage also got reduced initially… But when i have tweaked the pot associated with the second IC555 ( PWM control ), i could make the voltage reach more than 4.0 V average, hence the power too.

    So,,, i want to hear the valuable suggestions and corrections from your side to make this strategy into practical..
    On measuring the frequency at the gate terminals with PWM connected, i got nearly about 865 Hz. The Power output in the Bulb was stable. It didn't flicker or make any noises… So can i proceed with this pin strategy ?
    I will send you shortly, the current design pictures with output.
    I am waiting here to hear your suggestions and comments….

    With Regards,

    • Thanks Arun, that's great news!

      I won't be able to comment regarding the 3.0V issue unless it's verified through a scope.

      I think the culprit could be the triangle waves which are not equal to the supply voltage, it means even during the high pulses at pin3, the output would be less by 25%, which would sink the gate voltage by that much, so on an average this would be dragging the gate voltage to 3.0V average.

      It would be interesting to see what happens if we replace the square wave and the triangle wave positions in the above design…..square from IC1 to pin5 of IC2 and triangle wave to pin2 of IC2

  40. Sir in the last comment of mine,answered by you, i had actually asked you about the waves reaching the two secondary terminals of the transformer ( the terminals connected to each MOSFET drain points ), but you have answered for the output winding…. Think you will notice it.

  41. Sir, new problems are arriving…
    In the current prototype i am working with ( using CD4017 ), i can hear a squeezing sound by the inverter transformer when PWM is connected, this didn't effect the 100W bulb, it didn't flicker or show any disturbing effects.
    But the case changed when the bulb was replaced by a table fan ( 55 W only ). The fan rotated at maximum power when PWM was not used, but didn't rotate when PWM has been connected…. Then i checked the frequency at the output terminal of the inverter by connecting a 230/12-0-12 500 mA transformer as the load and checking its output frequency… I got around 1500 Hz…. About the same reading was detected at the gate terminal of the MOSFET….. I remember that, once you had told me that, the output frequency of the inverter will be exact 50 Hz even the gate terminals are fired using high frequency PWM waves… So why it is happening like this…
    – Does the result means, the gate terminals are not being fed with the real PWM waves ?
    – Then why did the bulb glow at that much high frequency ?

  42. Another problem is;
    As i have already said you that i am getting 330 V+AC output voltage..
    I have tried the output voltage regulation circuit..
    I got 390 V something DC on processing with the BR. Then tweaked the pot and inspected the voltage at collector terminal…
    BUT that voltage w.r.to ground was -ve voltages… Tweaking the pot gave variation from -7.0 V to -16.0 V…

  43. Sorry Sir… Last comment was a mistake…. Actually i didn't connect the -ve ( ANODE-ANODE ) junction of the BR to the ground, that is why the voltage appeared -ve…. it is due to my carelessness.
    Although the Output voltage doesn't respond on tweaking the pot… It remains at its high level…


    SO can i use the below given circuit for my application..

    In this circuit how the output voltage is getting stepped down to power the 741 IC ?
    The only one diode along with the capacitor acts as the half wave bridge rectifier.
    But, Will that resulting voltage not more than the maximum supply voltage of the opamp ?
    I can't see any voltage adjustments for the resulting voltage to suit for powering the opamp here..
    And also, Will the output voltage be suitable for this operation since it contains ripples compared to the full BR ?

  44. I forgot to ask you one thing.
    Will that 220 k, 15 K resistance combination act like a voltage divider instead of a pot ?
    I can't think so, since those resistances are placed prior to the rectification stage.. They are exposed to the direct AC. Think it would be better to place after rectification.

    • yes the resistor values are selected for getting around 14V, you can check it on any online "voltage divider calculator" software.

      It doesn't matter whether it's at AC or DC, the voltage divider will produce the calculated voltage across the selected output points.

      But yes, while calculating I should have used 310V as the input (peak) since it's this voltage that would be resulting after the half wave rectification, I used 220V as the input which is not correct….for getting 14V from 310V it should 10k instead of 15K

  45. thank you sir but my problem is the out put i don't get correct wave form at the transf out put so it could not handle ac fan well i sent you some pic and video please check it for me, i need your help im almost done so please help to succeed thank you homemadecircuits@gmail.com

  46. Sir.. Now the problem has been cleared. I got the real output of this circuit … Now the voltage at gate terminals are not getting reduced as before, thereby getting the same power output under PWM ( very small deviation can be found )…. Frequency at the gate terminals is showing 260 Hz something… The output frequency of the inverter ( found by using a secondary transformer ) was also found to be in the range of 50 to 60 Hz…. The bulb as well as the fan both worked perfectly.
    But two small problems remains unsolved;
    1). While a load is working, disturbing humming noise is heard ( especially when fan rotates )..
    So could it be possible to eliminate these harmonics completely by a second order low pass filter like this…


    Will there be reduction in inverter power if any of the filter is added at the output ?

    2).. The output voltage is still above 300V.. I have tried the simple opamp output voltage regulator..


    But the problem is that the transistor collector terminal is showing no voltage when the opamp output goes high.. I have checked the circuit separately ( without connecting to the gate terminals of the MOSFETs )……checked removing the zener diode to the base and connecting the 10 K resistor directly….but no response.. Pin#2 shows the correct reference voltage of about 5.0 V… I could also change the voltage at pin#3 using the 10 K pot, also got the output pin#6 go high at a point.
    For knowing whether the transistor responds to the opamp output voltage or not , i have checked the voltage between collector and the positive supply of the circuit… It always shows a constant voltage ( full supply voltage… No cahnge )

    Noted things :
    – Ground terminal of this output voltage regulator has been connected to the circuit ground
    -The Ac voltage across the 15 K resistance in the Divider networrk is about 14-16 V.
    -The Dc voltag created by rectification is also having the nearer magnitudes.

    The fact is that when i am connecting the 10 K POT as in the circuit, the AC voltage found across the 15 K resistor is getting reduced to a low value ( say 6.0 V ), so the DC voltage too… Maximum of 6.0 V DC i am getting

    Expecting your reply soon.

    • Arun, If the mosfet gates are not showing a reduced average voltage with the PWM stage connected it means the PWM stage is not working or has been rendered inactive.

      For the overload protection circuit the cut off switching at the collector will be so rapid that you won't be able to read the switch OFF time there.

      To visualize whether the cut off and self adjusting feature is working or not, just connect an LED in series with the base of the transistor, connect the zener diode also.

      Now suppose you have set this circuit to cut off at around 250V, the red LED will switch ON when this level is crossed and the LED will keep glowing as long as the output keeps producing the high voltage.

      Actually the LEd and the opamp switching would be oscillating ON/OFF at a very high rate but won't be visible to the eye.
      However this rapid ON/OFf switching of the opamp/transistor will make sure that the output voltage is controlled at 250V and not allowed to exceed.

      Now if the output drops below the 250V mark, the opamp output will switch OFf and the LED will also shut off indicating a normal or lower voltage from the inverter, below 250V

      You must set and test the above things manually first and only after confirming the opamp behavior connect it with the final set up.

  47. ok sir thank you but sir i forgot to ask you something that confused me, in the 555 stage on your left hand side there's resister connect to the base of bc557 is it 2k2 or 27k cos i can see it well and sir this is very important question i need you to answer it for me in the 555 stage on your rite hand there's 1uf capacitor non-polar can i use electrolytic capacitor like 1uf/25v or 1uf/35v tantalum? cos 1uf non p is difficult to get it here sir,thank you.

  48. What is the problem behind reduction in the Supply voltage in the automatic regulator circuit when that 10 K pot is being used ?

    I have tried using preset as well as volume control, different valued resistances.. but nothing changed…. still the 15 V supply voltage is getting reduced to about 6 V initially connecting the pot. Further reduced on tweaking the pot… So supply to the IC becomes variable. Some times reaches 3.5 V..
    The supply is getting reduced to 3.0 V even on connecting the 1 K resistance to pin#2…

    I will send you the video to your email… plz check it soon

    • Arun, please tell me what is the logic behind measuring the supply voltage of the opamp.

      You should measure and check whether the output mains is getting controlled or not.

      By the way the opamp supply voltage will get proportionately reduced if the output mains gets reduced because the voltage divider input is derived from the mains, so it means the circuit is working.

  49. But.. the initially i have tested the circuit with the AC from wall outlet ( which is constant 230 V )…
    So what variation to have occurred there ?
    I have said that, the supply voltage is getting reduced to a low value ( say 2.5 V ) by connecting the pot or the resistor at pin #2 at this constant ac voltage…
    How it is possible for the OPAMP to work properly at this low voltage ??
    It has been also noted that the supply voltage reduction is less ( say 4.6 V from 6.0 V ) on connecting a 10 K resistor to pin#2 instead of 1K….
    but i am fed up with that 10 K pot.

    • Arun, I think you have connected the preset wrongly otherwise there's no possibility of this happening.

      the center lead must go to the relevant pin of the opamp.

      you seem to get fed up without investigating the fault

  50. The connection was correct…. Center of the pot to pin#3 of OPAMP other terminals respectively to Sensing voltage and ground…
    It z not the problem due to any wrong connections… Then why it is happening the same by connecting the 1 K resistance between the Supply voltage and pin#2 ?

    • where did you connect the output of the opamp, or the transistor collector through the diodes.
      I really don't know how and where you have used the circuit, so please give all the possible details.

  51. Sir
    The circuit has been set up initially as a separate testing mode, not incorporating inverter output. The input 230 AC voltage ( under which the inverter output has to become stable ) is given directly as in your circuit… THat 230 V has been taken from the normal house wall socket..
    All the circuit components were placed as is on the given circuit… I have not connected the output of the circuit ( transistor collector through the diodes ) to any point.. It is kept free.
    But i am getting wrong results even before connecting the transistor stage…. When i am connecting the pot as said before or connecting the 1 K resistance the changes in voltage are very discouraging ones…. I will send the complete pictures to your mail.. Dn't 4get to check it soon…

  52. I have tested the circuit with replacing the 10 uf capacitor with other capacitors also…. but the result was same…. The interesting thing noted that, when i am connecting larger capacitors ( say 470 uf/25 V as is found in many ordinary rectification stages ) the produced DC voltage is getting increased slightly from a low value ( say 2.8 V ) to its maximum…

  53. ok sir thank you sir please take a look at this if it good to get this voltage at the pins,sir in the ic2 i got 9.31v at pin3 and ic1 i got 6.0 v at pin13 so sir it good?

  54. Sir can you suggest any method to identify a sine wave and square wave generated by a circuit separately without using any graphical means such as OSCILLOSCOPE TRACES ??

    • Arun download "goldwave" free version in your PC, and then you can use this software for monitoring the waveforms on your PC screen,

      But remember the input signals will need to be first converted to 1V PP before feeding your PC MIC socket..

  55. Could you please suggest a circuit for enabling the connection from high power output voltage from the inverter to the laptop MIC socket ?
    Since i am not so much confident about myself for making such a design to be used with my laptop i am seeking for your help

    • Try an online "voltage divider software" and select R1/R2/input prarameters appropriately for getting the 1V output.

      After this you can make this configuration for acquiring the 1V output

  56. ok sir,please sir if i connect the diode where the black mack is to the pin 6 and 7 of ic ne555 the sine wave work but it cannot adjust the RMS to get out put 220v A/C but if connect it as it is the sine wave don't work sir all i mean is that the 10k pot cannot be adjust the RMS if the 1n4007 diode is connected,

    • when the capacitor C charges, the slow rise in the voltage will pass through the diode and go to pin5 of the 555 via the pot adjustment, so I cannot see any reason how the diode can stop this from happening.

      check your diode polarity or may be it's faulty.

      Anyway if you don't want the diode you can remove it and use the 10k preset directly in the shown position.

  57. ok sir thank you sir please check the wave form i sent it to your email address homemadecircuits@gmail.com sir i think it shouldn't be like this any help? so that i can get the wave form correct with this wave form it handle small 220v a/c fan the speed of the fan is ok but the moment connect another load the fan stop waking i use 200ah 12v batt with 9-0-9 transf.

    • Biannz, it looks very impressive, but please let me know how you got these waveforms, for additions did you do for getting such waveforms.

      did you connect a 0.22/400V capacitor at the output, and is the RMS = 220V???

      You cannot get better waveform than this, because it's a modified sine wave so please don't expect to get a real sinusoidal type waveform.

      Also you may try increasing the output capacitor to 0.33uF/400V and check the response.

      I would be publishing the waveforms in the above article so that others can also visualize it.

  58. ok sir thank you,so you mean this wave form is alright?but you said that it equivalent sine wave not modified sine wave cos modified sine wave don't look like this or? ok sir help me with this if i connect 220v fan it run very good but if add another load like 60w bulb the voltage reduce so the fan stop.

    • yes this wave looks alright since it's the outcome or the resultant of the PWMs applied at the primary.

      The transformer is not able to support higher loads because its winding may not be rated to handle that much load…..use thicker wire for the secondary…and/or increase the AH rating of the battery.

      The power handling capacity is not anyway related to waveform or PWM of the circuit.

  59. ok sir please you said that inductor can be use so im asking you that where it should be connect and how many turns, this wave form is (2ms and 5 volt/DIV) sir i think i have succeed in this circuit so what i need is low battery cut off so sir can you please design one for me? thank you.

  60. sir please it good to get 70HZ out put? cos when i set it to 50hz the more i load the more it going up it not stable,please sir if i want to connect inductor where it should be connect ,sir can this circuit handle 24v dc batt and how to connect it thank you sir.

    • biannz, 70Hz is not good.
      use 7809 IC for supplying the 555/4047 IC positives from the battery.

      once you do the above, you can use 24V also without worry. use the 24v battery in the same position where presently the 12V is.

    • daniel,

      instead of using the mosfet gates for pwm control, it's better to use pin9 of the IC 4047 for applying the pwms, ……do the following:

      first disconnect pin9 from ground and connect it to positive via a 10k resistor.

      take a BC547 transistor and connect its colector to pin9, emitter to ground and base to pin3 of IC2 (555) via a 10k resistor…diodes are no longer required.

      now your mosfet section is free so that you can connect as many of them in parallel.

      make sure the gate of each mosfet has its own 100 ohm resistor and also put a 1k resistor across each mosfets gate and source.

  61. ok sir

    please im confused sir cos you said should connect to positive i don't understand the word via it is (with) or what? 10k resistor please can you update it for me co what you said confuted me

    • via means "through", meaning the mentioned connections must not be joined directly to the respective points, rather they must be connected in series with the mentioned resistors.
      if possible i'll make the diagram and update it

  62. ok sir
    i did it but it didn't work i don't know maybe wrong connection,please make the diagram and update it for me cos i want to make a bigger to see if this inverter is good for my need thank you sir hope to hear from you son.

  63. hi sir
    please i finally build this circuit but still big problem i used four fets two at one side and two at other side so total four,if i power the circuit the fets got very hots if i set the frequency to 50HZ it got hot and if set up to 60HZ the same problem i change all the 555 and cd4047 please i now i need your assist thank you.

    • Hi Daniel in that case you can revert to the previous concept and use the PWMs on the mosfet gates.

      for adding more mosfets you can use 4049 NOT gates and terminate their outputs with mosfets.

      I'll try to update the idea soon…

    • daniel you can do the following steps:

      we have 6 NOT gates inside a 4049 package

      connect the inputs of three NOT gates in parallel meaning join them together, connect this joint to one of the outputs of the 4047 IC VIA A 1K RESISTOR.

      Now connect the individual outputs of these gates to three separate mosfets via 100 ohm resistors.

      join all the drains of these mosfets to one of the outer taps of the trafo.

      Repeat the above procedure for the other three NOT gates and configure them with the other output of the 4047 IC and the trafo tap.

      After completing the above you can integrate the PWM input at the junctions of the NOT gates and 1K from the 4047 outputs.

  64. sir
    please as im talking to im on it but it didn't work maybe the connections are wrong connected sir i tried to send you the diagram but we are having a problem with our network so please can you try to update it for me?thank you.

    • daniel, please draw the schematic as per my previous instructions and send it to me, I'll check it for you and confirm its accuracy or make the necessary corrections in there are faults.

    • daniel, please draw the schematic as per my previous instructions and send it to me, I'll check it for you and confirm its accuracy or make the necessary corrections in there are faults.

      here are the instructions:

      we have 6 NOT gates inside a 4049 package

      connect the inputs of three NOT gates in parallel meaning join them together, connect this joint to one of the outputs of the 4047 IC VIA A 1K RESISTOR.

      Now connect the individual outputs of these gates to three separate mosfets via 100 ohm resistors.

      join all the drains of these mosfets to one of the outer taps of the trafo.

      Repeat the above procedure for the other three NOT gates and configure them with the other output of the 4047 IC and the trafo tap.

      After completing the above you can integrate the PWM input at the junctions of the NOT gates and 1K from the 4047 outputs.

    • daniel, please draw the schematic as per my previous instructions and send it to me, I'll check it for you and confirm its accuracy or make the necessary corrections in there are faults.

  65. Dear Mr. Swagatam Majumdar,

    Thank your for the circuit design schematic & breadboard pictures. Although difficult (for me), I enjoyed putting this together. I put together the last schematic on this page, with the BC547 included for parallel mosfets. It works nicely for me.

    I have not yet added parallel mosfets.

    I think my previous attempt to reply did not post because I had not logged in, so I will try this again.

    For the benefit of others, I wanted to mention that I had a few problems, mostly regarding having the wrong parts, and selecting the wrong values per the schematics. It took me a while to get it completed correctly.

    Let me see, I would guess that my biggest problem was with the capacitor and resistor at C1 and R1 of the 4047. I had to study the comments from the breadboard pictures in order to get that correctly. I had missed the period from other schematics, and had guessed at 22 uF (for C1). That was not correct, as it gave me a pulsed flash in about every second.

    For C1, I have tried .01uF and .22uF, both of which work for me. I am currently runing from .22uF, rated at 630 volts, per the comments regarding the successful breadboard trials.

    For R1, I am currently running with 22K Ohms, without P1 on the 4047. This works for me, but I suspect that I need to adjust the frequency in some systematic fashion.

    I do not have a oscilliscope, and I am in the U.S., so I have looked at the equations for frequency from some of your other posts. I suspect that I will buy an oscilliscope in order to check the frequency.

    I had ordered 2.7 volt Zener diodes, but when they arrived, I found that I had ordered 1/2 watt zeners, and not 1/4 watt zeners. The 1/2 watt zener diodes gave some slight flickering, so for the moment, I am using 1N4148 diodes. I will order the zener diodes again.

    I am currently running from three NE555's. I had bought 7555's from Radio Shack, but removed them to trouble shoot my problems.

    Finally, I have some small concern regarding the breadboard comments about the burned out mosfet, due to no protecting diodes. My front mosfet gets hot quickly, and I do not see the protective diodes surrounding the mosfets in the schematic at the bottom (with the 547 addition).

    I am running with IRFP150 mosfests, as I am having difficulty finding IRF150 mosfets. I also have IRF3105 mosfets, but am not currently using the 3205's.

    I think that the capacitor at C1 was my biggest problem there.

    Thank you very much. Although difficult (for me), I got a thrill from seeing it work!

    – Dave Hamm

    • Thanks Dave, for the great explanation!
      Yes an oscilloscope will be quite handy for checking the overall response of the system, and would also allow you to study the output waveform.

      In the meantime you could try varying the lower 10k preset and see if the output voltage also varies correspondingly, this will prove that the PWM section is working correctly as proposed in the article.

    • Thanks for the response.

      Yes, I did look at the 10K preset. I had done the calculations from your web page on "IC 4047 Datasheet, Pinouts, Application Notes" and calculated that P1+R1 should equal about 55 MHz when C1 is 0.22uF

      However, I have very little confidence in my understanding of your equations.

      I noticed a clue about the frequency when I had C1=0.22uF and R1+P1 = 22K. My little test 1 watt night light would give a humming sound that was quite noticeable.

      So, yes, I did place a 10K resistor in for P1+R1, leaving C1 at 0.22uF, and the humming sound of the night light went away as soon as the 10K (preset) was in place.

      Also, while using the 10K resistor in place for R1+P1, I did a test of a light load, a 15 Watt incandescent and let it run for about 45 minutes. During that time, the front mosfet (the lower one on your schematic) did not heat up hardly at all.

      Therefore, at first glance, it would appear that the 10K preset is much better than the 22K which I was initially using (while using C1 is at 0.22uF). I will leave it at the 10K until the oscilloscope arrives.

      On a side note, it also appears to be very energy efficient, which came as a pleasant surprise to me. I don't know the figures for efficiency, but it appears to have less drain on the batteries than I would have normally expected.

      Just wonderful to see it working.

      Thank you

    • Thanks Dave, actually I was referring to the lower 10K preset associated wit the first 555 IC from left.

      It's included for facilitating RMS adjustment or the average output voltage of the circuit.


    • Thank you dear Odon,

      I am very happy and excited to see the results…

      However I may have to delete this comment since you have posted your personal blog link, which I cannot publish.

      If possible please post the comment without this link and I'll make sure all the info gets published in the above article.

    • Sir can i ask your help. Can you give me a circuit of pure sine wave inverter that is atleast 300 or 500 watts 12v-220v dc-ac inverter 50-60 hz that is easy to build.

      Hope you will aswer.

    • Hello, sir:

      I don't understand how transformers work very well, so please forgive me if this is a dumb question. My Vin is 12 Vdc, so should I get a transformer that has the Voltage input of ~12 volts? Also, I found out that most transformers have 6 and 12 Vout. I can't find transformers that have 5 and 10 Vout. Could you briefly how this works? Thank you!

    • Hello phil, if your AC requirement is not bipolar meaning alternating from positive to negative and vice versa then probably you wouldn't require a transformer at all, but if it's bipolar then you would require a trafo as mentioned in your comment itself….primary should be rated with 12-0-12 and the secondary with 5-0-5v….you may have to get it designed specially from a transformer maker..

    • Thank you so much.

      May I have one more last question? If I don't use a transformer and my Vin is 12 Volts DC, then what would the output Vac be? would it be 12 V AC?

  66. Thank you Engineer for your help, but please can you help with the value for R1+P1 and C1 because i don't understand how they came by the 50hz frequency. Is there a mathematical formular for this?

  67. Mr Swagatam I found this on the blog for 4047 ic frequency calculation
    f = 1/8.8RC at pin10 and 11
    Where f is in Hz, R in Ohms and C in Farads.
    Engineer correct me if we choose the values Odon pick thus P1+R1 =22k and C1 = 0.22uf and calculate for frequency. I got this 8.8*22000*0.22uf=42592 but since 0.22 is in uf i divided the result by 1million to get the farad f. So 42592 divided by 1m =0.042592
    Now for frequency 1/0.042592=23hz If this is true then the actual f is not even 50hz.
    please sir correct me if am wrong.

    • Mr.kinnajingo, the best and the simplest way to confirm it is by connecting a frequency meter across the relevant pins of the IC..
      Your formula and calculations may be correct but the final confirmation will need to be done using a frequency meter.

  68. accross the output of this circuit could an inductor be placed to filter wave form if so what value could I use?

    I see 2 schematics is the one without the 1n4148 diodes at the gate of the FETS the modified version?

    what is the value of P1 connected to the 4047 ic?

  69. Thanks for the quick responds. Engineer I want to know if I want to add a driver stage where will i put it and what values will be best. I add a driver to the circuit with bc547 as transistor and 1k as the gate resistor from the ic. What i observe is that one side of the fets was heating. When i remove the fets and drive the fets directily there was no heating. all the test was done with no load connected. When i check the voltage from bc547 it was almost as high as the battery voltage and when i remove it and check the voltage from the ic it was around 4,2v, The reason for the driver was that i want to add more transistors and use a bigger transformer.

  70. if i am using a 12 volt battery source to this circuit my transformer would have to be a 6v centre tap? but since the ic can only manage 15v then adding a source voltage over that would require a regulator to limit it to probably under 16v so wouldnt that just allow the use of a 6-0-6 transformer.

  71. to the far left 555ic is the zener diode 27v or 2.7v?

    and the resistor below it is it 2.2k or 22k?

    can I get r1, c1 and p1 values

    what can I use to replace bc557 I am only getting replacement parts to buy.

    and I can only get ne555 not (7)555 can I use 3 ne555

    • 2.7V zener and 2.2k resistor

      r1,C1, P1 will need to be adjusted by practical monitoring for the required vrequency

      any low power PNP will do for BC557

      any 555 IC will do

  72. Aoa. i am new one here. i am making this circuit same as it is given above.
    Does it work properly?
    Please tell me the value of P1, R1 and C1 in 4047?
    I am using FET IRF640(18A, 200V) instead of mention you above.
    Give me answers separately
    Also i have 12-0-12 to 220 AC V, 5A transformer.
    Kindly give me a proper all components values in mail adnanmuhammad171@gmail.com
    I have short time please reply me as soon as possible. Please

    • P1, C1, R1 will need to be selected by practical verification using a frequency meter for getting 50Hz or 60Hz as per your requirement.

      the mentioned FET and the trafo will work, you can use them

  73. Thanx for your reply me. I saw many websites for my project, your one is the best. Dear admin I required 50Hz frequency.
    so, tell me the values of P1, C1 and R1 and send me a list of components values if you have for this project PLEASE. I 'll be very thankful to you

    • Thanks Muhammad, you can easily do it by manually setting P1 and simultaneously checking the frequency with a frequency meter across the output pins.
      value of R = 2.2k and C = 1uF/25V

  74. finally a working inverter form me from your page, and yet its not the simplest.

    I was getting voltages fluctuating between 105v and 138v, do I need to add a voltage control circuit to correct that? I didnt test with load because i didnt have a battery with me only a 12v adapter with 1.5amp

  75. to determine the wattage its the battery amp hour along with transformers wattage, but what i want to know is now that I am using only a pair of irfz44n how much wattage will I be able to draw from it.

  76. ok thanks,

    I am facing a problem though with frequency the transformer is making a hum so I check the frequency its all the way up to 2khz

    for the 4047 section is used a 330k resistor and a 100k pot I dont know if thats the prob, I saw a schematic like that on the internet so i used those values.

    the 10k pot in the circuit doesnt adjust the voltage, but I realize voltage can be adjust from the 100k pot i used at the 4047 and for the 180k resistor I used a 250k pot and set the value to 180k but moving it around also changes the voltage but not the 10k pot and the main prob is the frequency, I also tried a 12v half amp transformer it actually gave me a more steady voltage 117-117.8v dont know if that will happen if I increase to a higher amp 12v transformer but I need help with the frequency.

    • the noise can be probably suppressed by adding a capacitor across the output of the transformer. It could be due to the PWM chopping.

      use 1K instead of the shown 10k preset, this will effectively help to adjust the RMS as per your requirements.

  77. i tried a 223 capacitor and I reduced the voltage to 2volts so I removed it, I tried a higher wattage 12 volt transformer and it fried the fets, I thought I would only get lower voltage from the output.

    at the 4047 I removed the 330k resistor and just use the 100k pot but the frequency got higher, I saw like someone in this blog used 22k so Im going to use a fixed 22k resistor and check the frequency after replacing the fets.

  78. I changed to 1k pot and removed 330k resistor and I am getting like 5khz, I am not even sure if the meter is reading it correctly but the transformer is squealing and gets warm and the voltage is correct using a 12 volt half amp transformer, and also now the 1k pot adjusts the voltage on the output so the only thing left is to get the frequency down.

  79. I didnt use the diodes I sent the clock signal to pin 9 of 4047 ic, I just replaced the 103 cap I used at the 4047 stage and used a 1uf cap and the frequency went all the way down if I used the 100k pot to adjust it but the voltage is now reduced to 1.5v and the transformer has a slow clicking sound now and still gets hot.

  80. I wasnt getting any voltage when I used the 2.2k resistor so i added a 100k pot in series just like on the schematic i was able to adjust it up to 13v but transformer got hot along with one fet and the frequency is at 50hz, so I need to get rid of heating and get the voltage back up, i used a 1uf 50v electrolytic cap.

  81. on the basic design with just the 4047 a cap and a pot I used (4) irfz44n's, and 4 1 amp diodes and I used my 5 amp transformer I got 118v I used a 10k pot and the frequency was about 400hz I changed the pot to a 250k and I could then reduce the frequency to 50hz but then it started to let the transformer hum and the input coils got hot i saw steem then I unplugged. I realize wen the frequency was high It didnt get hot, I tried a bigger transformer I couldnt seen any specs only knew it was 12ct and 110/220v out but it burst a fet as I applied power, so I am figuring its because of the 1 amp diodes but still cant figure why the circuit got hot on 50 hz at the correct voltage

    • a transformer will burn only under the following conditions:

      high voltage than the winding rating

      high frequency (for iron trafos)

      no frequency (only one transistor conducting)

      output short or overloaded.

  82. Hello sir….I got this as my final year project….after all futile search i got this site… i found this site really useful an easy to understand….. along with lots of other doubt my first query is that Is it possible to have output to the load and display on the oscilloscope together at the same time…????/ if yes can u please let me know the connections….

    • Thanks Riyanka, yes definitely you can do it, once you get the load working through the inverter output you could connect the oscilloscope across the load for checking the waveforms simultaneously,

      you can actually see the scope waveform images of the output AC posted in the above article as submitted by one of the members.

      be sure to use an isolation transformer while measuring the waveform.

  83. Dear,
    I am doing a small inverter only upto 60 watts.
    my load will be 2 * 15w cfl lamps.

    I will use the 4047 ic here, and what i wish to know was,
    1. After setting the RC values in order to get the desired frequency, if the output from oscillator pin is 50 Hz then at pins 10 and 11, will frequency be 50hz at both pins respectively or 25hz at both pins?
    2. Up to what maximum frequency the 4047 can oscillate?
    3. Can i use an LC circuit to enhance the o/p waveform to a near sine wave? is this possible here?
    If yes, can one LC stage be enough or may i need more? for the capacitance, should value be same if i connect more stages, or can i reduce on value if i connect more stages?
    Please help.

  84. hi, Swagatam Majumdar,thanks for the good works you are doing here and i appreciate all your earlier help. I want to ask if there is a way to integrate this 555 circuit into an sg3524. i have thought of the osc pin 3 of sg3524 but i need to know what your thoughts are

    • Hi oladipo, I don't think pin3 integration would work,

      with a SG3524 also you may have to follow the identical diode mosfet gate integration as done with the 4047 circuit

  85. I have test it today with sg 3525…. It worked great but i want to make sure from something… Is ic 1(555)[ramp generator work at 50 hz]…is ic2 (555) work at [2 khz with square wave]….i have used For ic2 (555) r=6.8k and c=100nf is that right… I have used for ic3 (555),r=47k and c=50nf is that right… Thank you so much for this great idea, great thanks.

  86. Thanks for reply… I have read your post… Iam really enjoy your circuits..
    But can i use sg 3525 instead of 4047…as i see on oscilloscope sg3525 give a normal square wave… But it have feedback… My inverter is working good with sg3525… Iam running washing machine on it… Its working great but with small noise… So i want to get a sinewave with a help of your circuit…i have tested today its working but when i have connect 555pwm… I see that the square wave pluses become smaller… And frequency is stable 56hz… Thanks for your reply and kindness.

    • OK great, but If the slight noise is the only problem, then I think it can be corrected by adding a capacitor across the output winding of the transformer, you can remove the PWM for the time being….

      Just a add a 0.22uF/400V capacitor right at the output of the inverter and see the response, if still it does not help. you can improve the same by adding a coil along with it.

  87. Ok.. But from where could pick electronic components.
    And how can I check if the sinewave circuit is working properly…
    And should i get a signal like in the pictures in the Post.. Thanks.
    Iam really want this sinewave cause i want to run refrigerator… My inverter
    Can run 1800 watt hairdryer… And its working properly… But the fridge can't run because its square wave… Thanks for your help.. Sorry to disturb you again.

  88. I have a 12v 2amp transformer without Center tap…. Iwant to use it… Can i drive it using half bridge… I know that fan7392 and ir 2110 is a high and low side mosfet driver… But i don't want to use them… Its not available in my country now… Is there any replacement… I don't want to use p-channel mosfet… Thanks again.

  89. Hi Swagatam , when connecting the two drain terminals to an oscilloscope i get a sinewave however when connecting these drain pins to the transformer i get no output,absolutely nothing. How should the transformer be connected?

    I connected like the following.

    Drain from top mosfet to transfomer 6v

    Positive from battery to center tap of transformer

    Drain of bottom mosfet to last remainting 6v

    using a 6v-0-6v/ 240v 50hz/60hz transformer

    please assist asap

    • Hi Wade, please specify the following:

      transformer amp rating or wattage

      battery aH rating

      and the load wattage.

      all the above must be equally rated for getting a noticeable output

    • Its a 4 amp transformer 48VA

      Im using a dc power supply at the moment and not the battery.

      I have also not connected a load, i just connect the multimeter to the outputs of the transformer.

      Thanks for your response

    • connect 12V car headlight lamps in series with the drains of the mosfets, and check whether or not these light up brightly..

      .no indication will mean no conduction by the mosfets or no gate signal…

    • I dont have 12V headlamps so unable to perform that test but regardless of the mosfets. Should i not get an output from the transformer if i take the outputs straight from pin 10 an 11 of the CD4047 to the transformer 6-0-6 inputs. Im using irf3205 mosfets. im puzzled why am i not getting an output from the transformer? please help

    • the IC output current can be extremely low, so these cannot be used directly connected with the trafo…you will have to use mosfets or BJTs to amplify the current.

      check the frequency at the pin10 and pin11 of the IC and confirm whether or not the IC is producing the required oscillating frequency.

  90. Sir thanks for replying my questions, anothing thing if more power transistor are added to the above circuit is there are possibilities that the output wattage would increase too?

    Is this inverter can power some electronic devices like for example TV, radio, loptop and etc. Without damaging it? Cause i have heard that modified sine wave inverter is not very well to run that kind of devices. However, in the positive side it very well to run the electrical devices such as light bulb and heater.

    Hope you will answer my question.

  91. Hi Mr Swagatam Majumdar! actually I constructed the inverter that you gave in your blog, my problem ,I have a different frequency output at pin 10 and pin 11.Why? Thank you

  92. also i dn confuse for the components that is connected to pin 7 of ic2 which is rated of 1mA it is a diode? if so what ia the complete value it was not mention in your design it makea confusion.

  93. Sir, this project uses PWM high frequency is generated.
    What type of transformer used: ferrite, siliceous iron (leaves EI).
    If you work with siliceous iron that Gauss value (Bmax) is designed.

    Thank you

  94. Thanks for this design
    I build the above circuit with SG3524 IC, I connect the 555 based output to pin 3 of IC 3524 and it works fine when I use it to power 100w bulb although I don't check to wave as I don't have instrument to do that
    My problem now is when I connect the output from the third iC555 to pin 11 and 14 with 1N4148 as shown in the circuit above it doesn't work at all. So please where can I connect it to or I should leave it?

    • you will need to adjust the PWM for selecting the correct RMS value with the pot…..try the third circuit from top. You can check the RMS variations by a DC meter also at pin3 of the IC2

  95. Hi

    thanks for your help i have actually build this circuit the last one i.e. the fed to pin 9 of 4047 ic, i notice the frequency at pin 10/11 is not steady but i have steady frequency of 101 at pin of 13/2 of 4047 and the first ne555 also i have steady 101 at pin 5 of the third ne555 and steady 2.5khz at pin 2 of ic2 though i tested without load could it be the reason of the fluctuations at pin 10/11

    • I am not exactly sure about the issue, I think you should try the third circuit from top which has BJT buffers, and the PWM is fed to the base of these buffers instead of the mosfets. This configuration can be expected to be much reliable than the others.

  96. hi mr swagatam,how are you.
    congratulation for new site design,
    i want to share with you a pure sinewave inverter using pic16f72 microcontroller
    give your mail and i will send you files and you can share it here with all people.
    best regards

  97. Wouldnt it be more of a pure sinewave connecting a coil across the output of the transformer, what value coild could be used if so? also is the modified versin of the schematic a better version using the transistors before the fets? if so How would I add FEts in parallel?

    • LC can be used in conjunction with PWM for improving the results but without PWM it could be much inefficient.

      the bJT stage ensures better isolation from the PWM and a better discharge of the fet gate capacitance improving its performance.

      you can still add fets in parallel with the BJT by simply using individual gate resistors with each of the fets

  98. I built this just now I am having some problems I am wondering if one of the ic is giving an issue, or I am probably just using the wrong pot and capacitor on the 4047.

    1) main problem is that most times I applied DC power I don't get any output from the transformer if I don't turn the pot connected to the 4047 ic it comes on when the frequency is high, at times I will change around the capacitors and it come on at a lower frequency I am using 0.22uf sometimes I try 1 or parrallel 2 or even 3, I even try 0.1uf and also 0.01 one of the mixture alone with the 10k pot gave me 50hz at once but when ever I turn off the DC power and turn it back on the circuit won't come on until I adjust the pot to a higher frequency.

    2) voltage is good but I am actually getting a square wave output instead of the modified wave seen in the examples.

    3) link to pics

    • the issue could be with the IC specs, you can check the datasheet of the IC to see the optimal min/max values for the Rt, Ct

      if you are getting square waves then it means the 555 stage is not working…check the 555 stage separately and make sure pin3 produces varying pulse widths in response to the lower pot adjustments….

      check the pin3 of IC2

  99. OK thanks,I fixed the issue which was at the ic1, middle ic…. The resistor at pin 7 was shorted by mistake I connected it correctly and I got a better wave, also where you have a 180k resistor I have a 250k pot for me to get 50hz I have to adjust that pot clockwise all the way and then add (3) 0.22uf caps in parrallel across pin 1 and 3 of the 4047 and adjust the pot on the 4047 to get 50hz at 125v…

    But then I realized the resistor at ic1 kept smoking so I thought because of the short I damaged the ic, so I changed the 555 and also changed the resistor again but the samething keeps happening, so what I did was to add a 1k resistor in place of the 100ohm it's a 1watt and it works fine now, doesnt really get hot, but I realize the reason why the 100ohm got hot is because of the way i turned to 250k pot all the way down and what I realized is that across the pot I am getting 12.4v in which if I turn it back up where it doesn't get hot I have no voltage across it, so I am wondering if I should really leave it like that.

    The voltage I have it set to now is 124v and frequency at 56hz which I need 50hz but if I adjust it to 50hz the voltage goes all the way up to 134v and That may cause problem when testing electronic loads even though the voltage will drop when loaded.

    Link to wave form

  100. Ok will do.

    Also since its working the way it is now I am wondering if it can stay that way, I have a project coming up and I need 2 inverters a pure sine and a modifed sine I plan to use this as the modified sine thats why I didnt want to take out the triangle wave portion.

    Could you help me to achieve a pure sinewave also?

  101. I just noticed something rite where I have the problem at ic2 with the 100ohm resistor on pin 7, is that a diode connecting it to the collector of the transistor? If so I dont have a diode there and that would be the problem.

  102. Hi Swagatam Majumdar

    i really want to thank you for your assistance all this while. i have build a 2kva inverter of the above circuit and it work when tested. please i want to ask can this inverter withstand load? also can i incoporate feedback in other to withstand load if a feedback can be incoporate were can it be place in the circiut thanks and
    Best Regard

  103. OK then, since it's working as is im remove it from the proto type board and Solder it up, so I will need additives

    1) a circuit to cut off battery power probably at 10.5v and also cut off at 14.5v (just guessing a range)

    2)reverse polarity feature for the battery side or for both side,

    3) normally people talk about feed back what is that refering to really?

    4)low and high vtage alarm.
    Any other thing you can think of, to do this I guess I would redraw the schematic, which software do you use to draw

  104. question, about the reverse polarity seems as if thats for if the output of the transformer was the be shorted how would I connect the diode anode to battery positive and cathode to transformers center tap?

    What about reverse polarity protection on the battery side

    • the center tap diode is for protecting the inverter circuit from a reverse batt polarity.

      for protecting the battery from reverse charging current you can connect another diode to the batt positive..cathode to positive and anode open for charging input

  105. Ok you told me how to connect the diode to the battery cathode to positve and then leave the anode open for charging input, but what about how to turn the diode at the center tap of the transformer how do I turn that one.

  106. yes sorry I didnt read your previous message properly either.

    So I built this today on a larger scale and attacked a bigger transformer rewonded microwave transformer not sure of the wattage, but I only attacked 2 Irfz44n for testing the voltage was at 124v before load, when I added the fan and turned it on it went to 113v.

    Pcb boards online seem so very expensive there is no local manufacturer in my country that does Pcb, could you reccommend me to an online store that does it at a reasonable cost.

    Also did you do any Pcb for this design that would be handy.

    • I am sorry, I do not know about any online PCB manufacturer who can provide at a cheaper rate, by the way in which country are you in?

      I haven't been able to yet design the PCB for the above due to lack of time.

  107. I am in Jamaica we dont do electronics here at all we import all form of our electronics, we only repair here, I love electronics and I try to build every circuit that I see you upload just for fun, at times I end up building them and using them also.

  108. sure surprisingly I am now building circuits but I have a problem when I try to make inverters with large power since I need to use large cables I don't know how to connect those large wires to the fets I use and I cant find any type of connector I could connect to the fet the solder big wires to it, is there anthing you can recommend

    • how large are they?

      you can clamp them with nuts and bolts on the PCB, or you can fix by soldering using 100 watt solder iron

      or simply think about increasing the voltage spec…the current requirement will decrease proportionately

  109. I was trying to increase the power of this inverter by adding 4 irfz44n to each side but when I do that they keep blowing up as I apply power, before applying power I ensure to check for short circuit across the legs and there is none and only 1 side of the fets keep blowing up, I used 10ohm resistors fr gate resistance but on 1 side I used some 3 watt 10ohms and on the other side I used some 1/4w 10ohm resistors and the side that keeps blowing all the fets is the side with a 1/4w resistors I am wondering if thats the problem or is it that I should use higher gate resistor, probably 100 ohms.

  110. i lov dis inverter .have made some of ur inverters which worked pretty well.bt i want to make dis cos it sine wave n uv made it so simple.the problem am havin is how to add more power that is,adding more fets in parallel.u said d pwm integration should b connettd to pin 9 of d ic cd4047 as shown in d last diagram.bt other diagrams above shows pwm integration at the base of the bc547 transistors.am confused is it dat if i want more power i should use the last diagram.pls xplain to me .waiting for ur reply.thanks

    • I would recommend the second schematic from top, which uses BJT buffer stage.
      pin9 was just a suggestion but I am not sure about its outcome, so better to go with the earlier diagram using diodes and BJT buffers.

      for more power you will need a higher rated transformer and battery in terms of voltage, and lastly appropriately rated mosfets, the IC design is not relevant to the power outputs specs

  111. thanks for the quick response.wl make this after my exams and wl tell you how it goes.hope i can rate it upto 5kwatt and how can the voltage b made stable at 220v even with increasing load.thanks again

  112. pls need quick response.pls what is d name of the component you marked 1mA which is connected to the collector of bc557 and connected through 100ohm resistor to pin 7 of the last 555.tnk waiting for ur response.

  113. Hello sir
    The oscilator works with one energy saving bulb.but if I tried to increase the load. Eg TV or fan the inverter will not work.when I reduise the load the the bulb alone it will on.please what adjustment can I do to the oascilator

    • Hello yusuph, the output power will depend on the transformer wattage and the battery AH, so you will have to increase the ratings of these two parameters in order to be able to operate more loads at the output

  114. I've completed the oscillator,but little problem I encounter is that when I tested it with two energy saving bulb it works but when I try to include fan to it does not work.
    With sg3524 oscillator that I built it works perfectly. Please any idea of little correction I can make to the circuit

    • THe RMS value must be adjusted to make sure it is upto 230V, if the peak is 330V.

      there's no difference between the oscillation characteristic of 4047 and 3524, so IC is not the problem….the RMS needs to adjusted to the correct level for operating the fan.

  115. Sir,
    I searched the current rating of IC4047 and could not find it . It is required to decide the load capacity . So please help me to know the current rating of IC4047.
    Thank you sir

  116. Hi, I built this converter, I get 100hz on pin 5 and 2 kHz high frequency on pin 2 of the IC as you indicate. My problem is that I get 50hz on pin 10 and 11 of CD4047 when I remove the 10k resistor between pin 9 of the CD4047 and the positive (+). but it generates a high and different frequency at pin 10 and 11 of CD4047 when I connect this resistor. why? can I remove definitely this resistor or change for another value?what is the impact on circuit behavior?thank for your post

  117. Thank you, another problem please, I used two IRF3205 for a test, I get 220 V after adjusting the RMS 10k, the problem is the mosfet temperature is too high even if no load, it works about 1 or two minutes and one of the mosfet is damage. What can I do to solve this ?

    • remove PWM feed from the mosfets and check again, if the mosfets stop heating then the reason could be high frequency from PWM, reduce it to 200Hz or 150Hz and recheck.

      If without PWM it's still heating up then there could some other hidden fault in your design

  118. Hi, thanks for your post, I built this converter but I have some difficulty. If I use a 6V-0-6V transformer as you indicated with batery 12v , the mosfets will heat up to one minute and the output voltage will be approximately 350 volts without diodes and 400volts with two diodes connected.Why??? I get 50hz on pin 10 and 11 and 100hz at pin 13 of the CD4047.if I use a 15V-0-15V transformer I get 205volts at the output without the diodes and 220 volts with two diodes connected.and no heating at Mosfet, is it really necessary to use a transformer 6V-0-6V.help me,where is problem? thank you very very much

    • Hi, connecting the PWM should reduce the RMS voltage, it should not increase the RMS, I think you might have connected the diode in the opposite direction.

      I recommend the second diagram from top, which is more suitable for the diode PWM integration.

      please check the diagram again.

      6-0-6 is recommended so that the 350 voltage could be brought down to 220V after the diode (PWM) integration.

  119. Thank you very much, I finished to make it work,it's good to seen it , but is it normal that the transformer emits a sound? And how to integrate automatic voltage correction according to loads, I have already seen your old post for this but I have trouble for integrating it, can you send me a diagram to integrate it or explain how do ? Thank very much

  120. ok.According to you, which is better, using two battery 12volts 45ah in parallel with a transformer 6volts or two batteries 12volts in series with a transformer 12 volts? or it's the same performance?Thanks

  121. hello Mr.Swagatam. We are trying to make a project for wireless transfer of power using induction principle. For that we require high frequency inverter of nearly 20-50khz. Can u suggest how to trigger those MOSFETs. Thank you

    • Hello Hari, you can do it either by decreasing the associated resistor value or the capacitor value…or both together, for getting the desired level of high frequency output…increasing the values will decrease the frequency

    • the frequency is determined by the R/C components of the 4047 IC, you can try building the 4047 section separately and set the frequency first.

      if still it does not work then may be your IC could be faulty.

  122. Hi Swagatam
    It's great to see someone has built this inverter succesfully.
    I would like to know why you use current controlled generator for the sawtooth and PWM sections instead of a normal 555 oscillator

    • Thanks Robin,

      the current controlled stage ensures that the triangle waves do not get disturbed or change their specifications in response to a varying supply voltage, so this is specific reason for including the BC557 stage

  123. hi sir i have used ic 4047 and mosfets irf150 .first time the circuit runs properly but whenever we apply load after some time of first test then the ic is not working properly.i have used 12V battery of 7 amph. ic gives only oone pulse. kindly suggest me the solution > thanaks

    • Hi, the IC has no direct connection with the load so it should not get affected by the load.
      use an IC socket for the IC and try other ICs to see whether the specific IC is faulty or it's happening with other ICs also….

  124. By the way do you guys realize the current draw from battery there is no load added, also the current draw is higher when it's running for the first minute then it's current draw goes down along with the output voltage.

    I haven't gotten the time to build the 4047 board alone as yet but I'll just separate the one I have from the others since I spilt the build in 3 and test it

  125. hello sir thanxx for sharing your knowledge …..i have made your simple circuit i got 220 volt ac o/p but its not suitable for my 100watt tv ,or Watt led bulb i think that device operate only pure sine wave .please is it possible to run 100 watt tv by using this circuit ?? ..i want to make 300watt pure sine wavw inverter.

    • Heelo Ravindra, the design explained in the above article can be used for operating all kinds of equipment, even your 100 watt TV etc. It is almost a pure sinewave inverter circuit….

    • Hi Colby, you can use a 30V supply but in that case make sure to replace the 100 ohm top resistor with a 7812 IC so that the ICs are supplied with 12V and not 30V…sorry I do not have a PCB design for this….anyway you must first try it on a breadboard before going for a PCB…

  126. I'm young king sir pls there is question I want to ask like u said that tip35 can accept minimum of 25 amps, now if I want to use more number of tip35 how do I determine my trans4mer amperage and battery amperage.I'm waiting for or responds

  127. if I want to produced output power of 500watts,50Hz
    which components do I change and at what ratings?
    also what would be the ratings of transformer to be used?

  128. I cannot suggest about pin#9 PWM integration circuit because I am not sure about its results.
    I would recommend the second circuit, and this circuit will also allow you to add extra mosfets in parallel.

  129. You will have to set the frequency by adjusting P1 and by measuring it practically at the output pin of the IC with a meter, I cannot say the exact part values. Frequency measuring facility should be there in your DMM, if not then buy one.

    first make the circuit using a single mosfet, if everything goes well then you can go for additional parallel mosfets.

    each mosfet should have its own gate resistor, the resistor ends must be shorted and joined with the BC547/BC557 emitter junction.

    I hope now you have understood.

  130. i have connected the circuit for pure sine wave inverter and the challange is if i try to connect load its damages the transistors,i have use two IRFZ44 transistors….what would be the problem or the cause?

    • connect reverse diodes across the drain/source of the mosfets and check the response, and also check the current consumption by connecting an ammeter in series with the battery positive, make sure this is not exceeding the mosfet max specification.

  131. Sir..
    I need to build for
    my home use…
    Which one can be
    use pure sine wave.
    I see 3 circuits diagram.
    They are not same.

  132. Thank for reply sir…
    I use second pic and draw my book.
    I want to know some parts.
    In Ic 4047 ,
    R1,P1,C1 their value in picture not show.
    IN first IC555,
    Resistor of BC 547 emittor show R
    and condenser collector show C
    can’t see their value sir.
    IN second IC 555
    Value of resistor can be 180k or 220K?
    I little to ask.
    All zena diode 2.7v can be replace
    2.7ZD can not buy in my country.
    I am crezy hoby in electronic.
    But i have not teach much.
    I live in myanmar country (Yangon).
    Thank alot for your teaching and project.

    • Hi Aye,

      for the IC 4047 R1/P1/C1 you will have to check the datasheet of the IC or any other 4047 50Hz inverter disgram online you will find many diagrams, from where yu can copy the values.

      That is not not BC547, that is BC557, please refer to the first diagram, the 555 section is clear in the first diagram you can copy the parts from there.
      you can use a 220K preset and adjust the output accordingly, however 180K will OK…

      zener diodes can be 4.7V or 3.3V

      Let me know if you have any more questions.

  133. I hold Sukam inverter Sinewave Model Sturdy. I noticed the mosfets are burnt and i replaced the burnt mosfets. Before that i have removed the Inverter transformet connections and finally noticed when i give the 12volts battery connection the mosfets burnt. I am unable to understand where is the issue. Can you help me in getting for any idea what could be the faulty?

    • Please check whether the gates of the mosfets are getting the required oscillations or not from the oscillator stage…because if the mosfets do not oscillate then the mosfets will keep burning….

  134. I hope you have used Darlington transistor at pin#5 of IC2?? using two BC547

    do the following:

    1) check the frequency at pin#3 of IC1 555 and make sure it is reaching IC2 555 pin#2
    2) initially keep the emitter of BC547 disconnected with pin#5 of IC2 555 and apply an external varying 0 to 12V supply at pin#5 directly, check the pin#3 of IC2 555 for a varying PWM in response to this…you can check this by attaching a 12V flashlight bulb across pin#3/ground of IC2 555. make sure to connect the negative of the 0–12V with the negative of this circuit while checking

    If the bulb light varies in response to the varying voltage then your IC1/IC2 are working OK.

    now connect back the emitter to the pin#5 and check the response again from the triangle wave generator IC 555by varying the 10k preset.

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