DC/AC power inverter

250 to 5000 watts PWM DC/AC 220V Power Inverter

This is my schematic design of a Pulse Width Modulator DC/AC inverter using the chip SG3524 .
I have built this design and using it as a backup to power up all my house when outages occur.

See more details and the full article that I posted at Instructables.com, click here


-The schematic circuit design is for a 250 watt output, while the pics are of my 1500 watts inverter that i built, to increase the power of the circuit you have to add more of the Q7 and Q8 transistors in parallel, each pair you add will increase your power by 250 watts, ex: to get 750 watts of power from the inverter you need to add 2 of Q7 and 2 of Q8 to the original design.

–If you increase the power transistors you have to enlarge the T2 transformer to match the new needs, the circuit’s transformer is rated 25 amps to handle 250 watts of 220v, for every 1 additional amp you need on the 220v side you have to increase 10 amps on the 12v side, of course there are limits to the thickness of the winding so if you need more than 750 watts i recommend that you use a 24VDC supply instead of 12 volts:

DC voltage and Transformer “T2” winding recommendation:
Power     Supply     Winding
750w       12VDC     P:24V “12-0-12” / S:220V
1500w     24VDC     P:48V “24-0-24” / S:220V
2250w     36VDC     P:72V “36-0-36” / S:220V
3000w     48VDC     P:96V “48-0-48” / S:220V
3750w     60VDC     P:120V “60-0-60” / S:220V
4500w     72VDC     P:144V “72-0-72” / S:220V
5250w     84VDC     P:168V “84-0-84” / S:220V
*The transformer should be “center tapped” at the primary side.
**You can make the secondary 110v if needed.
***The transformer in the pic is a custom made (48V center tapped / 220v ) 2000 watts, weights like 10 kilos.

–R1 is to set the PWM to 220v
–R2 is to set the frequency to 50 or 60 Hz

–Use either tantalum or polyester film “as in pic” for the 104 caps, ceramic disc caps change value once hot and this in turn changes the frequency of the inverter so they are not recommended.
–Wiring should be thick enough to handle the huge amps drain from the batteries.
–The design does not include a battery charger since each person will be building a custom version of the inverter with specific power needs.
–A cooling fan will be needed to reduce heat off the heat sinks and transformer, i recommend getting a 220v fan and connecting it to the output T2 transformer, when you power up the circuit the fan will start this will always give you a simple way to know that 220v is present and everything is OK..

–2 circuit breakers are recommended instead of fuses, one on the DC side and one on the AC side, depending on your design
Ex: for a 24vDC ( 1500 watts design ) put a 60Amp breaker on the DC side and a 6Amp on the AC side.
For every 1amp of 220vAC you will be draining like 8 to 10 Amps from the 12v battery, make your calculations !

— The 2 Heat sinks should be big enough to cool the transistors, they are separate and should NOT touch each other. “see the pics”

–“Optional” : Deep Cycle batteries are your best choice, consider them for best results .. read more

–Be cautious when building this circuit it involves high voltage which is lethal, any part you touch when the circuit is ON could give you a nasty painful jolt, specially the heat-sinks, never touch them when the circuit is on to see if the transistors are hot !! I ate it several times 🙂


46 Responses to DC/AC power inverter

  1. Jonathan Spicer says:

    Very clever work, my friend. So, the schematic shown is a 250 Watts, 12v DC to 220v AC? Only one other question, does the thickness of the winding wires for the transformer matter in this case? Are you using a 220v AC to 12v DC transformer by just reversing the primary and secondary connections? Thanks in advance, and very creative work.

    Take care,

  2. Ranjithparanagama says:

    Please send me compleate details required parts for this circuit

  3. eldon says:

    Yes sir I can’t see your circuit clearly can u sen a clearer one plz

  4. Sarah Paul says:

    sir,could u plz send the full design of this circuit…(like how we get the value of the resistors,capacitors,etc..)

  5. sim says:

    why is driver transistors not used at the mosfet version

  6. Josivan says:

    Hello friend, very nice job.
    I would like to know…
    Is this power inverter of pure sine wave output?
    If no, do you know how can i have this kind of output? (What modifications i have to do is this schematic?)


  7. Josivan says:

    Thank you very much Nicolas.
    You’ve helped me so much.

  8. Josivan says:

    By the way Nicolas, I’m a Computer Scientist. I can help you with software program for PIC…
    I can help you for free, sure… If you need it, send me an-email ok?
    The only thing is i’m busy now, so i can’t do it so fast, but if you can wait a few I write programs to you if you need, ok?

  9. sundhar says:

    hi mr.nick zouein am sundhar from india. ur circuit deatails are very awesome.then i want need to quick charging for ur circuit.so please sent the details 4 quick charging circuit

  10. teewah says:

    Hi, I implemented your circuit concept , have been working on it for some time , but the output is not clean, would love a quick response.I can send you the output waveform.

  11. Godfred Obeng says:

    hi can I please use mj802 to replace 2n6277?

  12. Godfred Obeng says:

    Thanks Mr Nick for the reply but could u please help me on how to calibrate 2.2k variable resistor for a perfect overload protection and can I also use the pin 3 of the 555 to pin 10 of the SG and ignore the relay on the overload circuit?

    • it depends on the max. load you want your circuit to trigger.
      Ex: if you want it to trigger at 2amps then you have to load it with 2amps and calibrate with the 2.2k till it triggers.
      You have to test pin3 of 555 with the pin10 of the SG. mainly it should work.

  13. Godfred Obeng says:

    thank u very much for ur assistance Mr Nic, I do really appreciate it a lot but is it ok to use the inverter AC output to recharge the battery? and also could u please help me with mobile phone command circuit?

    • No you can not use the circuit to self recharge it’s battery. it doesn’t work this way.
      what mobile phone command?

      • Godfred Obeng says:

        I mean am building a different charging circuit but I will be using the inverter AC output to feed that charging circuit so the battery will be charging while de inverter is working and is it also adviceable to plug 5000 Watts stabilizer on 1200 Watts inverter?

      • Self charging does not work the way you’re thinking. As if you are trapped in some room and you’re eating from your own flesh to survive. It is exactly the same !
        A 5000W stabilizer would give out only 1200W and not 5000w if connected to a 1200w source. So it is useless, even it will consume some watts to operate itself. Do not use it.

      • Godfred Obeng says:

        and also will the load be on the inverter or the stabilizer? if the load will be on the stabilizer which means I can use it for my fridge, microwave, TV, fan and ironing? don’t mean to plug all of them @ de same time, one @ a tym I mear

      • both will have exactly the same load. I suggest you visit my more detailed page here.

  14. Danladi A Birdling says:

    Hi Nick, i built ur design(the one with SG) I used IRFP064 for the power and it was awesome . i used 12, 24, 36 and 48 volts they are all good.Thanx Nick u’ve contributed world of electronix.
    I want to try the pure sine wave. Can i buy the programed ICs from u?

    • Thank You, I always get happy when I hear that someone has benefit from the design.
      I don’t suggest you build the sinewave now, I’m not satisfied with it’s results, it’s doing all sorts of problems, unreliable. but check from time to time I’ll be updating it when I have time.

  15. Godfred Obeng says:

    Thank u very much Mr Nick for everything but can I @ least use the 1200 Watts for my 1 amp fridge, 800 Watts microwave and TV? I know I can’t plug my iron on it

  16. Godfred Obeng says:

    Hi Mr Nick, I have an old inverter which the circuit isn’t working and I’ve decided to use ur circuit to replace it but they fixed this high power diode P600j across the collector & emitters of the transistors & as u are the originator of ur circuit should I maintain them or I should remove them. the transformer is very powerful that I don’t want to spoil it that’s why am asking u please. thank u

  17. sundhar says:

    Sir your circuit will be support for high frequency transformer. Tell me sir

  18. Nicolas says:

    Hi Nic, I am here in Madagascar, I have realise your instructable power inverter in texto. I had a great succes for 5 exemplaires by your templete (1200W)! so thank you alot Nick.

    Nicolas S.J.

    • You’re Welcome ! 🙂

      • sundhar says:

        Hello nick am sundhar from India. Your pwm inverter circuit very awesome. I have high frequency transformer for using ur circuit. But output is not pure a.c.. your circuit support for high frequency transformer. Please tell me the solution….

  19. jluga says:

    sir can u post a power inverter circuit diagram that can drive a battery charger 5amps thanks,

  20. iyke says:

    thanks very much for the cct, it reall work well.but my curent rise up to 6amp when i put 2uf,pls help

  21. Peter says:

    please send the complete circuit would love to build it?

  22. Nick good day
    the site instructables is not loading oh I built this your inverter like 2yrs ago bit didn’t really workout fine for meee.. but this time i would get it 100% right.. and your site is difficult to sign-up oh.. please can you post all those your pictures here.. and this is some other thing I think would be helpful for people building this inverter.
    can you show us how to test each stage step by step to see if it’s working. checking the transformer wouldn’t be a problem together with the transistor.. I know you gave a hint on how to test the oscillator part but can you do it a step by step procedures.. so we could know our ossilator@ y part is working fine that’s the brain of the system..
    I have been a fan for years

  23. Waheed says:

    Hi Nik,
    please can you send me the details of the transformer winding calculation for this inverter rating. I mean the power rating, current, primary and secondary wire size.
    My email is oluyombowaheed@gmail.com

    Thanks and God bless.
    May God Almighty increase your knowledge sir.

  24. Waheed says:

    Hi Nick,
    Can you please guide me on how you determined the power rating, current, wire size of the transformer used.

    Thank you. May God Almighty increase your knowledge.

    My e-mail is oluyombowaheed@gmail.com

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