This is a heavy duty design of a Pulse Width Modulator DC/AC inverter using the chip SG3524 .
I've been using it as a backup to power up all my house when outages occur since aprox. 6 years non stop.

If you like the work and intend to build the circuit don't forget to click on the "I made it" button so I know how many people benefit from the design, Thanks.


1> 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 in parallel 2 of Q7 and 2 of Q8 to the original design.

2> 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" size recommendation:
(Power) (Supply) (Transformer 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.

Note15-Feb-16: (48V center tapped means: P:48V "24-0-24" / S:220V)

Note18-Feb-16: Test your transformer before doing this project. Disconnect the transformer from anything it is attached to, connect the 220v Secondary side directly into a 220vAC outlet and test the Primary side with your voltmeter, you should get exactly the voltage necessary for this project as per the table above. If not then don't waste your time building the project, it will not work.

****Do not supply the driver circuit with more than 24VDC max. because the voltage regulator "7812" will burn. Look at the pic of how to connect the batteries and where to take a 24vDC wire from.

3> R1 is to set the PWM duty cycle to 220v. Connect a voltmeter to the AC output of your inverter and vary VR1 till the voltage reads 220V.

4> R2 is to set the frequency to 50 or 60 Hz (R2 range is between 40Hz to 75Hz), so guys that do not have a frequency meter are advised to blindly put this variable resistor mid-way which should drop you in the range of 50~60 Hz.
If you want you can substitute the variable resistor with a fixed resistor using the following formula: F = 1.3 / (RxC)
in our case to get a 50Hz output we remove both the 100K and the variable 100K both from pin 6 and we put instead a 260K fixed resistor and we leave the 0.1uF (the 104 cap) as it is, this change should give out a fixed 50Hz as per the formula :
1.3 / (260,000 ohm x 0.0000001 farad) = 50Hz
But in reality it will not exactly give 50Hz because the 260K resistor has a specific error value margin so does the capacitor, that's why i recommend a variable resistor so that accurate calibration can be achieved.

5> Use either tantalum or polyester film "as in pic" for the 104 caps, ceramic disc caps are heat sensitive, they change value when hot and this in turn changes the frequency of the inverter so they are not recommended.

6> Pin 10 of the SG3524 can be used to auto shut down the inverter, once a positive voltage is given instead of negative to pin10, the SG3524 will stop oscillating. This is useful for persons wanting to add some cosmetic makeup to their inverter like "overload cut-off", "low battery cut-off" or "overheating cut-off".

7> Wiring connections on the power stage side should be thick enough to handle the huge amps drain from the batteries. I marked them with thick black lines on the schema also I included a pic so you see how thick those wires must be. (You can make the driving circuit section on a breadboard for testing purposes but NOT the power stage).

8> The design does not include a battery charger since each person will be building a custom version of the inverter with specific power needs. If you are ordering a custom made transformer you can ask them to take out for you an additional output wire on the primary side to give 14v (between point 0 and this new wire) and use it to charge a 12v battery, of course this needs a separate circuit to control charging auto cut-off. But anyway this is not advisable because it will shorten the life of the transformer itself since using it as a charger will toast the enamel coating layer of the copper wires over time. Anyway .. YES can be done to reduce cost.

9> 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.. You can use a computer's old power supply fan if you like.
Note that the fan must suck air out from the inverter case and NOT blow inside, so install it the correct way or it will be useless.
Also note how I fixed both the heat sinks and where the fan is, in a way that the fan sucks hot air from like a channel between the 2 heat-sinks.

10> 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 !

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

12>Important: If you're building a big design that uses more than 24VDC as power source, make sure not to supply the driver circuit with more than 24v maximum. (EX: If you have 4 batteries 4x12 = 48v , connect the v+ supply of the driver circuit to the second battery's (+) terminal with a thin 1 mm wire which is more than enough. (This supplies the driver circuit with +24v while supplies the power transformer with +48v) "see the batteries pic example"

13> "Optional" : Deep Cycle batteries are your best choice, consider them for best results .. read more

14> 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 :)

15> The optional "Low voltage warning" is already embedded in the PCB layout, you can disregard it and not install it's components if you do not need it. It does not affect the functionality of the main circuit, it just sounds a buzzer.

16> The Motorola 2N6277 is a durable heavy duty power transistor, it is used in many US tanks for it's reliability but unfortunately it is a very hard to find part, instead you can substitute each 2N6277 with 2 x 2N3773 or any equivalent, and yes equivalents work too.

17> I've included an optional "Battery level indicator" circuit diagram that has 4 LEDs, you can see it installed on the front panel of my inverter pic, it is functioning great and shows precisely how much juice the batteries still have. I have included a small relay that is powered by the last LED to auto shutoff the inverter once last LED is off.

Update 18-Feb-16: There are cheap readily available, professional looking Battery level indicators these days for a couple of $, consider them in your project. LED meterLCD meter

18> Also included an optional "Overload circuit", it is very easy to build and can be calibrated to the desired overload current threshold cutoff point through the potentiometer VR1.
R1 is rated 5watts for inverters upto 1000 watts. For bigger versions of the inverter like 1000 to 3000 watts inverters, replace R1 (1 ohm, 5watts) with (1 ohm, 17watts) which should handle loads upto 10 VA.
Make sure you install a proper relay to handle big current drains.

19> Please guys take your time to read and understand my notes, browse and read the posts and questions asked by others because there are many useful information listed in replies. The main reason for me not answering your question is because it has already been asked before and answered upon.

20> It would be nice and inspiring for others if you take some photos and show us how you built your version, any additions to the circuit are mostly welcomed to be listed here, we can all benefit from them.

21> Please click on the "I've made it" button/icon if you did build the circuit so I know how many people benefit from this design.

22> Testing the circuit on a
breadboardwith crocodile clips or thin wires WILL NOT WORK ! You'll get wrong voltage readings. Don't come back crying that you're getting a 150v output or so.

<p>Please how can i download the pdf file</p>
<p>Please how did you make the pcb?</p>
I made it. And it work better thanks
<p>Hi Nick, I have started this project with some scrap parts from a broken down old ups. The original design was very inefficient. I'll add more pics as I go along.</p>
<p>Good morning sir, I made this and it work nicely. </p><p>Many thanks for sharing this. God bless you</p>
Thank you for your project
I'm yet to make my due to lack of vR1
<p>hi neck , </p><p>thanks for your good work , i made a 1 k watt inverter based on your scheme and it worked but there is one problem : it is draining 5 amps from the battery without any load attached to it !!! any idea ?! </p><p>best regards ,</p>
Hi bros pls I need the full circuit diagram I cant see it clearly with instructible pls help
Hi Firas,<br>The filter capacitor may be causing this, disconnect it and try.
Hi please I want to build a 2000watts inverter can I use the circuit like that without change any component?
<p>Hi I have a 48v center tap transformer. However when I test the transformer on a 220v supply, I get 26v. Can this transformer be used for this application? Is there a design to charge the batteries in series?</p>
<p>Oops. I didn't see that you are using SG chip for getting the two PWM signals. Ok.</p><p>Can I use PIC32 with two Complementary SPWM signals instead and retain the same Power stage of IRFP250 and same 168V-220V transformer for 5.25 KW Inverter</p>
<p>I am going to build 5250W Inverter. I will be using IRPF250. I want to know how many Mosfets I have to use in the two banks. Also What should be the primary and secondary that is 84-0-84V side and 220V side current ratings of the transformer ?</p>
Hi<br><br>Where can I get the transformer for 5 KW Inverter ? What will be its approx cost ?<br>Are you generating two SPWM signals from PIC which are complementary ? If yes, Can I use PIC32 to generate two complementary SPWM signals using 128 points in half sine wave ?
Hello, thanks for the circuit diagram. I have carefully followed your instruction. I was able to setup the driver stage successfully but I am having problem with the power stage. I used Ń-channel mosfet MT3205 using the mosfet schematic. Anytime I connect the inverter to test, the ground terminal of the battery connected to the source of the mosfet get burnt immediately. <br><br>I now increased the thickness of the wire and retest, after I connected the battery, after 2 seconds, the mosfet blew up. I tried again with another set of mosfet and they all blew up again. Please help me.
I need to convert 24v to 220v by i c cd4047 i have transformer 12.0.12 100Av
<p>Hi <a href="http://www.instructables.com/member/ShadiA12" rel="nofollow">ShadiA12</a>,</p><p>You can't. Look at my notes #2</p>
<p>Hi? Do you have a complete parts list of the driver stage e.g capacitor voltages?</p><p>Thanks.</p>
<p>hello</p><p>can you send me library of sg3525 and tlp250 ( lib and idx) proteus files.<br>My Email: nesrine-elec@hotmail.fr</p>
<p>hello sir, i'd like to try your schematic but with the use of pin 10. how do i wire the overload cut-off, low batt. cut off as well as the low batt. indicator??thanks in advance</p>
can we replace that microcontroller with arduino
<p>That is not a microcontroller. but if you intend to ask whether the project can be implemented using arduino, you certainly can. </p>
Sir I have a problem.. sir I make mosfet version circuit . I use transformer ferrite E core type for only 30 watt. Sir problem is mosfet heat up immediately when I on the circuit and also transformer loudly produce hamming noise... sir why it was happening .. i use input 12 v 7 Ah only. Give me a suggestion plz.
<p>Hello Nick,</p><p>wondering what your thoughts were on a 300A 15v regulated power supply? How to, I have some ideas but will lil to get your input.Note system is 24vdc to 15vdc step down...</p>
Nick sorry. But u know it is a complete upgrade of yours with little similarities. Anyway i will update my site and mention You and ur site for Credit. Thnx
This site provides a circuit with a single transformer for everthing. Charging, feedback etc. http://freecircuitworks.blogspot.com/2016/04/solar-inverter-circuit-with-charger.html
<p>I posted this on your website where you copied my work:</p><p><a href="http://www.instructables.com/id/250-to-5000-watts-PWM-DCAC-220V-Power-Inverter/" rel="nofollow">Nick_Zouein</a><a href="https://freecircuitworks.blogspot.com/2016/04/solar-inverter-circuit-with-charger.html?showComment=1459873284245#c8501724037360038870" rel="nofollow">April 5, 2016 at 5:21 PM</a></p><p>You can at least say that you copied this design from Nick Zouein (instructables.com). Give credit to other people's work.</p>
<p>pls i saw a similar in this link</p><p><a href="http://freecircuitworks.blogspot.com/2016/03/solar-inverter-circuit-with-charger.html" rel="nofollow">http://freecircuitworks.blogspot.com/2016/03/solar...</a> but this time it uses a single transformer for everything, Charging, pulse with and inverting i want to know if its possible that way</p>
<p>Hello, why are you using feedback to PWM controler, this inverter frequency is synchronized with grid?</p>
<p>hello man</p><p>are you have any application note for SG3524 or tc4422?</p><p>how we can control inverter's switch using micro-controller like AVR or PICs? are you have any shematic of this circuit?</p>
<p>thank's sir, i have build this design over and over and it works perfectly work. i always make use of IRF250n as my driver.</p>
<p>hi nick ,</p><p>i made a 1000 watt inverter using your design with automatic switching to charging mode when there are electricity and itworked,i loaded it with 850 watt drill and 100 watt light bulb , but i have 2 problems :</p><p>1- the transformer (which i've made ) making very high noise at inverting stage , but no sound in charging mode !</p><p>2-as i said i loaded it with 950 watt, but that was when i attached it to 12v 100Ah battery which was attached to a charger so the input voltage was about 14v and the output then was 220v , when i removed the charger , and without any load , the fire started in the mosfets after 30 seconds !!</p><p>i used 6 irfp260 mosfets , i sent feed back , didn;t put diods to the transformer .</p><p>can you help me with that please ?!</p>
<p>i love this instructable</p>
<p>i love this instructable</p>
<p>i love this instructable</p>
<p>i love this instructable</p>
<p>Hey buddy.. I want to know that can i use this inverter to directly attain 220v from solar panels? I have 2 solar panels (24V 215W 9A each) and 2 batteries (12V, 200A and 250A resp. Can i use this system of yours. Kindly reply or mail me at owaisbinshahid@gmail.com or whatsapp at +923369657739. m waiting for your response ASAP </p>
Cod! Choisoqdoog@gmail.com
<p>I have seen a similar design to this one on instructables, which was advertised as a pure sine wave, although technically i believe its a pwm stepped modified sine wave that is filtered to near smoothness. What I want to know, is this design sufficient to run sensitive electronics such as a PC power supply? </p>
Here's the picture of the board.
<p>Nice clean work !</p>
<p>Hello</p><p>I made the PCB from the picture of the backside, the one of the built board.</p><p>I can't use TIP122 and I have to drive the 2N3773 directly from the board as the TIP122 burn the gates of the 2N3773 (they aplly 12V instead of 7V max gate voltage of the 2N3773).</p><p>With this I can power a 20W bulb but voltage drops to 200V. I have a 600VA transformer and I get 12V by powering it from 220AC.</p><p>I power it from a 10A power supply and current and voltage on it stay stable also under load.</p><p>Can someone help me?</p><p>I'll do the test by powering the transformer from the 12V side and also to connect a load on it in theese days.</p>
<p>Hi,</p><p>Replace the BC's with the TIP's, this way they will not be 100% saturated from the oscillator. Anyway they should not 'burn the gates' as you say. </p>
<p>Hello</p><p>Nice project</p><p>Would it be possible to have the pcb file of the board with Low voltage warning?</p><p>Because it isn't downloadable.</p><p>Giulio</p>
<p>is anyone from India is in .... Please reply me way phone or email </p><p>mailbox.sabut@gmail.com 09585135851</p><p>You can also text me in whatsapp </p><p>Because I need somebady help , my friend take this as his final year project so he need some help</p><p>Please guys reply me as soon as possible </p>
<p>Thank you for your sharing ! but i have some questions related to power stage parallel mosfet IRFP250. In datasheet, IRFP250 have power dissipation 190w. what is power handling of IRFP250? and how can i calculate power handling of IRFP250 in datasheet ?</p>
<p>I have used 2N6033 power transistor in place of 2N6277. My circuit is working till the power transitor 2n6033 but i am not getting the output. my transformer is 12 volt to 220 volt and 25 amp. am i using a wrong transistor? Please help.</p>
<p>This my first at instructables, can this be modified to do 24v to 240V at 2500-5000Watt?<br>Where do I get the stuff?<br>Do I have to make the PCB myself.<br>I&acute;m a retired Software Engineer, who once was an Electronician.</p><p>Thanks for the good effort</p>

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