3 High Power SG3525 Pure Sinewave Inverter Circuits

The post explains a 3 powerful yet simple sine wave 12V inverter circuits using a single IC SG 3525. The first circuit is equipped with a low battery detection and cut off feature, and an automatic output voltage regulation feature.

This circuit was requested by one of the interested readers of this blog. Let's learn more about the request and the circuit functioning.

Design#1: Basic Modified Sine

In one of the earlier posts I discussed the pin out functioning of the IC 3525, using the data, I designed the following circuit which is though quite standard in its configuration, includes a low battery shut down feature and also an automatic output regulation enhancement.

The following explanation will walk us through the various stages of the circuit, let's learn them:

As can be witnessed in the given diagram, the ICSG3525 is rigged in its standard PWM generator/oscillator mode where the frequency of oscillation is determined by C1, R2 and P1.

P1 can be adjusted for acquiring accurate frequencies as per the required specs of the application.

The range of P1 is from 100Hz to 500 kHz, here we are interested in the 100 Hz value which ultimately provides a 50Hz across the two outputs at pin#11 and Pin#14.

The above two outputs oscillate alternately in a push pull manner (totem pole), driving the connected mosfets into saturation at the fixed frequency - 50 Hz.

The mosfets in response, "push and Pull the battery voltage/current across the two winding of the transformer which in turn generates the required mains AC at the output winding of the transformer.

The peak voltage generated at the output would be anywhere around 300 Volts which must adjusted to around 220V RMS using a good quality RMS meter and by adjusting P2.

P2 actually adjusts the width of the pulses at pin#11/#14, which helps to provide the required RMS at the output.

This feature facilitates a PWM controlled modified sine waveform at the output.

Automatic Output Voltage Regulation Feature

Since the IC facilitates a PWM control pin-out this pin-out can be exploited for enabling an automatic output regulation of the system.

Pin#2 is the sensing input of the internal built in error Opamp, normally the voltage at this pin (non inv.) should not increase above the 5.1V mark by default, because the inv pin#1 is fixed at 5.1V internally.

As long as pin#2 is within the specified voltage limit, the PWM correction feature stays inactive, however the moment the voltage at pin#2 tends to rise above 5.1V the output pulses are subsequently narrowed down in an attempt to correct and balance the output voltage accordingly.

A small sensing transformer TR2 is used here for acquiring a sample voltage of the output, this voltage is appropriately rectified and fed to pin#2 of the IC1.

P3 is set such that the fed voltage stays well below the 5.1V limit when the output voltage RMS is around 220V. This sets up the auto regulation feature of the circuit.

Now if due to any reason the output voltage tends to rise above the set value, the PWM correction feature activates and the voltage gets reduced.

Ideally P3 should be set such that the output voltage RMS is fixed at 250V.

So if the above voltage drops below 250V, the PWM correction will try to pull it upward, and vice versa,  this will help to acquire a two way regulation of the output,

A careful investigation will show that the inclusion of R3, R4, P2 are meaningless, these may be removed from the circuit. P3 may be solely used for getting the intended PWM control at the output.

Low Battery Cut-of Feature

The other handy feature of this circuit is the low battery cut off ability.

Again this introduction becomes possible due to the in built shut down feature of the IC SG3525.

Pin#10 of the IC will respond to a positive signal and will shut down the output until  the signal is inhibited.

A 741 opamp here functions as the low voltage detector.

P5 should be set such that the output of 741 remains at logic low as long as the battery voltage is above the low voltage threshold, this may be 11.5V. 11V or 10.5 as preferred by the user, ideally it shouldn't be less than 11V.

Once this is set, if the battery voltage tends to go below the low voltage mark, the output of the IC instantly becomes high, activating the shut down feature of  IC1, inhibiting any further loss of battery voltage.

The feedback resistor R9 and P4 makes sure the position stays latched even if the battery voltage tends to rise back to some higher levels after the shut down operation is activated.

12 Inverter with feedback control

Parts List

All resistors are 1/4 watt 1% MFR. unless otherwise stated.

R1, R7 = 22 Ohms
R2, R4, R8, R10 = 1K
R3 = 4K7
R5, R6 = 100 Ohms
R9 = 100K

C1 = 0.1uF/50V MKT
C2, C3, C4, C5 = 100nF

C6, C7 = 4.7uF/25V
P1 = 330K preset

P2---P5 = 10K presets

T1, T2 = IRF540N

D1----D6 = 1N4007

IC1 = SG 3525

IC2 = LM741

TR1 = 8-0-8V.....current as per requirement

TR2 = 0-9V/100mA Battery = 12V/25 to 100 AH

The low battery opamp stage in the above shown schematic could be modified for a better response as given in the following diagram:

24V inverter circuit with frequency adjust and low battery cut

Here we can see that pin3 of the opamp now has it's own reference network using D6 and R11, and does not depend on the reference voltage from the IC 3525 pin16.

Pin6 of the opamp employs a zener diode in order to stop any leakages that might disturb pin10 of the SG3525 during its normal operations.

R11 = 10K
D6, D7 = zener diodes, 3.3V, 1/2 watt

Circuit Design#2:

In the above section we learned the basic version of IC SG3525 designed to produce a modified sine wave output when used in an inverter topology, and this basic design cannot be enhanced to produce a pure sinewave waveform in its typical format.

Although the modified squarewave or sinewave output could be OK with its RMS property and reasonably suitable for powering most electronic equipment, it can never match the quality of a pure sinewave inverter output.

Here we are going to learn a simple method which could be used for enhancing any standard SG3525 inverter circuit into a pure sinewave counterpart.

For the proposed enhancement the basic SG3525 inverter could be any standard SG3525 inverter design configured to produce an modified PWM output. This section is not crucial and any preferred variant could be selected (you can find plenty online with minor differences).

I have discussed a comprehensive article regarding how to convert a square wave inverter to a sinewave inverter in one of my earlier posts, here we apply the same principle for the upgrade.

How the Conversion from Squarewave to Sinewave Happens

You might be curious to know regarding what exactly happens in the process of the conversion which transforms the output into a  pure sinewave suitable for all sensitive electronic loads.

It is basically done by optimizing the sharp rising and falling square wave pulses into a gently rising and falling waveform. This is executed by chopping or breaking the exiting square waves into number of uniform pieces.

In the actual sinewave, the waveform is created through an exponential rise and fall pattern where the sinusoidal wave gradually ascend and descend in the course of its cycles.

In the proposed idea, the waveform is not executed in an exponential, rather the square waves are chopped into pieces which ultimately takes the shape of a sinewave after some filtration.

The "chopping" is done by feeding a calculated PWM to the gates of the FET via a BJT buffer stage.

A typical circuit design for converting the SG3525 waveform into a pure sinewave waveform is shown below. This design is actually an universal design which may be implemented for upgrading all square wave inverters into sinewave inverters.

[caption id="" align="alignnone" width="640"]BJT buffer with mosfet Warning: If you are using SPWM as the input, then please replace the lower BC547 with BC557, Emitters will go to buffers, Collector to Ground, Bases to SPWM Input.[/caption]

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

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

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

Preferably, the PWM input frequency should be 4 times more than the base 50 or 60Hz frequency. so that each 50/60Hz cycles are broken into 4 or 5 pieces and not more than this, which could otherwise give rise to unwanted harmonics and mosfet heating.

PWM Circuit

The PWM input feed for the above explained design can be acquired by using any standard IC 555 astable design as shown below:

IC 555 pwm with pot and 1N4148

This IC 555 based PWM circuit can be used for feeding an optimized PWM to the bases of the BC547 transistors in the first design such that the output from the SG3525 inverter circuit acquires an RMS value close to mains pure sinewave waveform RMS value.

Using an SPWM

Although the above explained concept would greatly improve the square wave modified output of a typical SG3525 inverter circuit, an even better approach could be to go for an SPWM generator circuit.

In this concept the "chopping" of each of the square wave pulses is implemented through a proportionately varying PWM duty cycles rather than a fixed duty cycle.

I have already discussed how to generate SPWM using opamp, the same theory may be used for feeding the driver stage of any square wave inverter.

A simple circuit for generating SPWM can eb seen below:

generating sine pulse width modulation or SPWM with opamp

Using IC 741 for Processing SPWM

In this design we see a standard IC 741 opamp whose input pins are configured with a couple of triangle wave sources, one being much faster in frequency than the other.

The triangle waves could be posibly extracted from a standard IC 556 based circuit, wired as an astable, as shown below:

triangle wave from IC 556

This forces the opamp to compare the two coinciding peaks of the waveforms and generate SPWM or sinewave PWM consisting of a proportionately widening and narrowing PWMs in each cycle.

When this optimized PWM is fed to the first circuit design causes the output from the transformer to produce a further improved and gentle sine waveform having properties much identical to a standard AC mains sine waveform.

However even for an SPWM, the RMS value will need to be correctly set initially in order to produce the correct voltage output at the output of the transformer.

Once implemented one can expect a real sinewave equivalent output from any SG3525 inverter design or may be from any square wave inverter model.

If you have more doubts regarding SG3525 pure sinewave inverter circuit you can feel free to express them through your comments.


A basic example design of a SG3525 oscillator stage can be seen below, this design could be integrated with the above explained PWM sinewave BJT/mosfet stage for getting the required enhanced version of the SG3525 design:

Simple IC SG3525 inverter configuration

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

Courtesy: Ainsworth Lynch

SG3525 chopped inverter using IC 555

PCB design of SG3525 inverter circuit

Design#3: 3kva Inverter circuit using the IC SG3525

In the previous paragraphs we have comprehensively discussed regarding how an SG3525 design could be converted into an efficient sinewave design, now let's discuss how a simple 2kva inverter circuit can be constructed using the IC SG3525, which can be easily upgraded to sinewave 10kva by increasing the battery, mosfet and the transformer specs.

The basic circuit is as per the design submitted by Mr. Anas Ahmad.

The explanation regarding the proposed SG3525 2kva inverter circuit can be understood from the following discussion:

hello swagatam, i constructed the following 3kva 24V inverter modified sine wave (i used 20 mosfet with resistor attached to each, moreover i used center tap transformer and i used SG3525 for oscillator).. now i want to convert it to pure sine wave, please how can i do that?

Basic Schematic

My Reply:

Hello Anas,

first try the basic set up as explained in this SG3525 inverter article, if everything goes well, after that you can try connecting more mosfets in parallel.....

the inverter shown in the above daigram is a basic square wave design, in order to convert it to sine wave you must follow the steps explained below The mosfet gate/resistor ends must be configured with a BJT stage and the 555 IC PWM should be connected as indicated in the following diagram:

SG3524 with BJT buffer stage

Regarding Connecting parallel mosfets

ok, i have 20 mosfet(10 on lead A, 10 on lead B), so i must attached 2 BJT to each mosfet, that's 40 BJT, and likewise i must connect only 2 BJT coming out from PWM in parallel to the 40 BJT? Sorry am novice just trying to pick up.

No, each emitter junction of the respective BJT pair will hold 10 mosfets...therefore you will need only 4 BJTs in all....

Using BJTs as Buffers

1. ok if i may get you right, since you said 4 BJTs, 2 on lead A, 2 on lead B, THEN another 2 BJT from the output of PWM, right?
2. am using 24 volt battery hope no any modification to the BJT collector terminal to the battery?
3. i have to use variable resistor From oscillator to control the input voltage to the mosfet, but i don't know how i will go about the voltage that will go to the base of the BJT in this case, what will i do so that i want end up blow up the BJT?

Yes, NPN/PNP BJTs for the buffer stage, and two NPN with the PWM driver.
24V will not harm the BJT buffers, but make sure to use a 7812 for stepping it down to 12V for the SG3525 and the IC 555 stages.

You can use the IC 555 pot for adjusting the output voltage from the trafo and set it to 220V. remember your transformer must be rated lower than the battery voltage for getting optimum voltage at the output. if your battery is 24V you can use an 18-0-18V trafo.

Parts List

IC SG3525 Circuit 
all resistors 1/4 watt 5% CFR unless otherwise specified
10K - 6nos
150K - 1no
470 ohm - 1no
presets 22K - 1no
preset 47K - 1no
0.1uF Ceramic - 1no
IC = SG3525
Mosfet/BJT Stage 
All mosfets - IRF540 or any equivalent Gate resistors - 10 Ohms 1/4 watt (recommended)
All NPN BJTs are = BC547
All PNP BJTs are = BC557
Base Resistors are all 10K - 4nos
IC 555 PWM Stage 
1K = 1no 100K pot - 1no
1N4148 Diode = 2nos
Capacitors 0.1uF Ceramic - 1no
10nF Ceramic - 1no
Miscellaneous IC 7812 - 1no
Battery - 12V 0r 24V 100AH Transformer as per specs.

Need Help? Please send your queries through Comments for quick replies!


Sharoj Al Hasan said…
Sir i cant make any electronics circuits because of i cant identify Emitter Base and Collector properly. i am using Digital multi miter . Sir please help me
Swagatam said…
Refer to datasheets of the concerned devices and you will be able to find the pinout arrangement instantly
Thanks for the lecture I will try and see the difference thank you very much for sharing.
Rohan said…
First of all thank you for publishing that much of hard work free for any body to use. Also could you please tell me how you limit or achieve 4-5 pulses in each 50Hz cycle. Does it happen automatically once you connect BC547 to SG3525. Thanks,
Swagatam said…
Hi, Thanks, it is initiated when PWM is fed at the bases of the two BC547 transistors shown at the bottom of the first circuit.

The PWMs can be generated using the recommended circuits using IC 741, IC 555
First of all, I would like to thank you for your dedication to help others.
Thanks for publishing the modified sine wave inverter SG3525. Some days back you published a modified sine wave project with TL494. I wish to assemble one. Could you please suggest me, which one is better with features to assemble for my home? I need an inverter with capacity of 500 to 1000watt.
Thank you, Benjamin
Swagatam said…
Thank you Benjamin,

both the ICs are significantly similar with their working specifications and features so it doesn't make much of a difference as far as performance is concerned. You can try the one which is more suitable to you...

the power output will depend on the mosfet specs and the battery AH rating

Good morning and thank you for your prompt reply. I shall assemble one of the two circuits and reply you. GOD Bless you.
With regards, Benjamin

Swagatam said…
You are welcome Benjamin!
hello swag...thanks for your time and effort you take to answer questions and designs, i would like to ask this ..can the arduino be used to generate the oscillation to drive the mosfets and the pmw to feed the two BC547 ?
Swagatam said…
thanks solomon,

according to me, an Arduino can be programmed and used for generating the basic mosfet oscillations and also the PWM oscillations together from its respective pinouts.
victory said…
In the ic555 circuit what is the function of the pot and what single resistor will be used in place of it for generating 4 times the base frequency? and also will i eliminate the feedback feature of the sg3525 using a 6-0-6 500ma transformer 3.if i want to add more mosfet in parallel will i use seperate 50k resistor at it's gate 4.if i build this circuit will it produce a mains ac similar waveform that can get rid of the humming of inductive loads like fan when connected to modified sinewave? thank you.
Swagatam said…
the pot is used for setting up the PWM for the inverter, and it cannot be replaced with a single resistor since it needs to be precisely adjusted for fixing the RMS value.

the fixed resistor determines the frequency

yes the feed back mess can be eliminated if the above explained method is employed, but make sure the all the circuits are supplied from a fixed voltage source using 7812 IC.

parallel mosfets can be added without any modifications.
with some filtration at the output the results could be quite similar to pure sinewave
Grertingt Lord am an amateur and need to ride the full vircuit diagran with SG 3525, IC 555 and transistors BC 547, BC 557 with list of components. Thank you
Greetings Lord am an amateur and need to ride the full circuit diagram with Sg 3525, IC 555 and the list of components. Thank you
Swagatam said…
If possible I'll try to upadte the complete design soon...
thank you sir swagatam for the cooperation that has always been with us. I hope the entire circuit when you can
Swagatam said…
Thanks Fransisco, I have updated the basic SG3525 oscillator circuit in the article, I hope now you will able to do the remaining integrations which is not difficult.
baasit yusuf said…
Hi Mr swagatam,
I really appreciate your grate jobs and ideas shares with everyone. MORE POWER TO YOUR ELBOW AND GOD WILL BLESS YOU SIR.

I've done many of your design and everything works perfect.

I want to try this as well and I will need you to guide me through if any challenge. once I finish I will share

Swagatam said…
...if you have problems, let me know about it...
Swagatam said…
It's my pleasure Basit. I am glad my circuits are serving the purpose for you.

I wish you all the best with this project....

baasit yusuf said…
Many thanks for your response,
Can I use bc337 in place of bc557? I'm working on the circuit now
Swagatam said…
BC337 is NPN, whereas BC557 is PNP
baasit yusuf said…
Many thanks, I later find some 557 in one of design that I'm not using again.

I have two questions
1. Can I use 50k preset in place of 100k preset?
2. Can I use bc337 in place of bc547 aside need two more to complete the circuit and I can't get it around where I stay.
Swagatam said…
50k preset will do.

BC337 will work instead of bC547

greeting Mr. Swagatam I have some questions about the circuit 3525, I found the coil L2 100uH, I can do, and as frequency and voltage will be regulated and if you apply the 12 vol directly to the 3525 and 555. See you later.
Swagatam said…
L2 is actually not crucial you can eliminate it if you wish to...

using a 7812 could be included for ensuring a stabilized output, although this too might be not crucial...
Ainsworth Lynch said…
I just saw this post I havent been here for some time, in the past I normally asked you for pcb of the circuits you make but it would normally be a case that your too busy. I have been doing some practice over the last couple months and I am now successful in building designing the pcb's and also making m own boards, I know im not as good as the professionals but for the simple circuits I build they work well for me.

I was just reading this article and was trying to put everthing together so I could make a pcb but I think I am not understanding something, ouu uploaded a basic design with the 3525, I am now wondering where should I send 2 output pins on the 3525 to:

1) An opamp?
2) the same bjt stage you have?

or would I need to make 2 triangle oscialator circuits to feed 2 opamps then send the outputs to the base on the bjt section of the inverter and also connect the output from the 3525 to the base of the bjt's also.
Ainsworth Lynch said…
I read it over just now I understand I can use the basic 3525 diagram and the bjt output stage and also feed the pwm input to the pwm input section on the bjt stage.

What I dont understand is the SPWM, I understand the concept just dont know the frequencies that I should feed the opamp with, how high and how low should the frequencies be by guessing I would make the fast one 200hz and the slow one 50hz my expected output is 50hz at the inverter's output.
Ainsworth Lynch said…
I just made a drawing.

Swagatam said…
1) it's clearly indicated that the 3525 outputs are supposed to join with the "BJT/mosfet stage"....meaning with the two 10k resistors at the bases of the BJTs...

the opamp and triangle wave stages are associated with PWM generation.
Swagatam said…
yes 50 and 200Hz could be tried...
Swagatam said…
It looks good, if possible could you please connect the 555 pot center lead with pin2/6, and send it back so that I can publish it here....
Ainsworth Lynch said…

this contains a pcb I did of the drawing also.
Ainsworth Lynch said…
since the SPWM method is better I would like to draft up the circuit for that also but I am having probs finding triangle wave circuits to match the 50hz and 200hz output I need at the correct voltage which should be 5v I assume.

You could help me out with that I would go through your page and do some drawings of the tested circuits but i'm not sure of all those you tested, you could send me some links of circuits you dont have time to draw up and I would do them and some pcb also if you like.
Ainsworth Lynch said…
Also I found this just now that you made and it seems to be a good circuit, was it tested?


Would any modifications need to be done to this for the waveform to run sensitive electronics?
Swagatam said…
OK great, thanks so much, I'll update it soon in the above article!!
Swagatam said…
a 555 IC astable circuit could be used for obtaining reasonably good triangle waves, it could be extracted across the timing capacitor of the astable.

two such circuits could be built for developing the slow/fast triangle waves and integrated with the opamp inputs

5V may not be critical, although a 7V supply for the 555 ICs would enable you to get 5V triangle waves...
Swagatam said…
a simple LC network at the output of the transformer would help to neutralize the harmonics and improve the waveform, although this may not be entirely critical
Ainsworth Lynch said…
Ok then ill test that version of the inverter since it has so much features.


I hope it works well, ill make a pcb for it also.

I would like to add the LC network, commonly I would see 0.1uf 400v not sure what value inductor to use.
Swagatam said…
sorry, I think I misunderstood the link,,,,actually it is just an ordinary sg3525 design, and the features are nothing significant, the output will be crude modified square wave, not good for sensitive electronics, and it cannot be improved using LC network without huge losses.

actually I thought you were referring t this link

Ainsworth Lynch said…
Oh no, I was refering to the sg3525 circuit with protection features, so I guess I can't build that one then.

Which circuit would you recommend me to build that has the best sine wave.
Swagatam said…
the above explained looks the most appropriate one....and can be further enhanced by adding an automatic battery charger....which is not difficult.
Swagatam said…
Ainsworth Lynch said…
When you say above are you talking about the one in this article


Swagatam said…
The one which is published on this page, because the linked one is not a pure sinewave.
Ainsworth Lynch said…
I'll just add the battery charger circuit to the drawing, do you have any schematic you recommend.
Swagatam said…
you can probably try the second design from this article

Ainsworth Lynch said…
I thought you said battery charger circuit... Thats a low battery cut off circuit... But it's still handy I'll include it also.
Ainsworth Lynch said…
Also I would apply a 12v battery to the circuit in this article, is it OK to use a different 12-0-12v transformer or will I have low voltage?
Swagatam said…
the second design is an automatic battery charger, may be you did not check the circuit thoroughly
Swagatam said…
it should be a 9-0-9V transformer otherwise the output could be below the normal level even at battery 13V
Abubakar Sani said…
Good day sir,
Please can these two upgrade circuits be incorporated with output pin of SG3524 IC to achieve the same sine waveform?
If not, please help me out with an upgrade because i have a circuit of SG3524 and wants to upgrade it to a sine.
Thank you sir.
Swagatam said…
Hello Abubakar, yes the concept can be easily implemented with SG3524 based circuit also, in fact with any squarewave inverter....you can use a 4047 inverter, TL494 inverter 4017 inverter etc....the PWM/BJT stage explained above is a universal sinewave generator design
Ainsworth Lynch said…
Do you know any good companies that I can buy transformers from for these projects, a company that isn't that expensive.
Ainsworth Lynch said…
In that case I could supply a 48-0-48v to the circuit and use a 45-0-45v transformer because I want to modify this to 6000 watts, I was thinking to use some irf3205, would 6 pairs do?

6000 watts at 48 volts would be 125amps I'm wondering if I can get that transformer made.
Swagatam said…
I have no idea about it..
Swagatam said…
yes that would be fine!
the output waveform is also modified Sine wave
Hello Sire I want to firstly appreciate your efforts... your blog has really helped electronic novies like me.
Sire if I generate a sine wave using an op amp an feed it to the two identical bjt(547) will it work? Or should I still use a triangular wave ?
Hello sir. I really want to appreciate your efforts..your blog have being so helpful to me.
Sir if I generate a sine wave using an op amp(ua741) and then feed it to the identical transistor(bc547) below will it improve the output? Or should I still use the triangular wave?
Swagatam said…
Thanks christopher, it is possible, as explained in the following concept, you can refer to the last diagram for the complete design

Sir,how to check wave of inverter? because wave meter not available in my area.please sir guide me.
Swagatam said…
buy an oscilloscope, there's no other way of verifying waveforms
hello sir i made this circuit but the sine wave is not completely give any advice please.
How to check inervter wave? without oscilloscope I will share you give mobile headphone and conect pin11 and 14 of ic sg3525 and 10k register in the serise of the headphone we hear the wave sound.sir my English is very weak don't angry on me.sir how to post image
By me?
bursach said…
Hello, Swagatam, is there any chances to get these files like Eagle pcb files, or sch?
Ainsworth Lynch said…

Request the pcb file but send the link to this page so I can be sure of the circuit that you need.

Is that ok Mr Swagatam I can send you the pcb files for you to post up or link it to my Google Drive incase someone needs it.
Swagatam said…
Hello Bursach, it could be difficult from my side due to lack of time..a PCB designer will easily do it for you
Ainsworth Lynch said…
Remember I did the pcb design I can send it to him, is that not allowed?
Swagatam said…
you can definitely share it with anybody you want....there are no such restrictions.
bursach said…
Thank you both, it will be very helpfull, I can send you my email if it is now allowed to attach here.
Swagatam, I can share a Eagle pcb for automatic slide gate controller from your site, tested and worked, if somebody wants to make it.
Swagatam said…
Thanks Bursach, you can provide your email here or you can contact Mr. Ainsworth for the files.

bursach said…
Thanks again, my email: bursacmilan@hotmail.com
Ainsworth Lynch said…
OK i sent you Gerber files for the pcb, let us know if it was successful after testing.
bursach said…
Thank you Ainsworth, I will let you know! Kind regards!
Abubakar Sani said…
Good day,
I saw your recent post mr. Ainsworth about sg3525 sinewave/modified sine wave pcb design.
Please i would like to ask you some questions about pcb design and inverter circuitry and i will be greatful if you give me your time.
This is my email please.
Thank you.
Ainsworth Lynch said…
Questions about the inverter should be asked here, I can talk to you about the pcb design though, Mr Swagatam is the designer of the circuit.
Ainsworth Lynch said…
MR SWAGATAM I have updated most of my inverter designs with the BJT stage and was ready to present you with an article but I realize something, wouldn't these inverters still need output voltage correction
Swagatam said…
I have already published one related article, you can refer to it below, and add it to your finalized design

Ainsworth Lynch said…
do you have any schematic with a feedback circuit coming from the output transformer?

Dont you think thats a better method?
Swagatam said…
the above link which I provided you is linked with the output of the transformer.
Hello sir, thanks for this very good tutorial....this circuit is a pure sine wave or modified sine wave ??...thanks
Sir, I can use the driver IR2110 MOSFET in place of the transistor? In the circuit SG3525 has pin 9 can I use 100n capacitor in place of 10n?
Swagatam said…
Hello Matt, it's a pure sinewave with an appropriately selected capacitor connected at the output of the transformer
Swagatam said…
No, replacing the shows BJTs is not recommended,you can select the mosfets as per your choice but the BJTs should be as indicated
Thanks sir, sir i now if i want to stop the SG3525 i can put the pin 10 of the ic in high state..but how i can do to stop the ic NE555 ?? Thanks sir
Swagatam said…
Mattlander, it can be done by configuring pin#4 of 555 to positive through a 10k resistor then connecting a BC547 transistor collector with pin#4 of the iC, emitter to ground and base to the shut down high logic through a 10k resistor.....but it is not required because shutting down SG3525 alone will be enough to shut down the output
bursach said…
I think pin 10 of SG3525 can be without connection to negative, just stay free. And if you want, you can add a relay with plus (+) to com and NO or NC depends of state and connect to pin 10.....
Swagatam said…
sorry that's not correct, preferably it should be connected to ground either directly or through a capacitor to avoid stray pick and instability

relay can make it unnecessarily complicated
baasit yusuf said…
Hi Mr swagatam, it's been a while, I really value and appreciate your response / effort just to make someone like me to be able to do something on my own.

I've completed the design but I need oscilloscope to check the wave form in which I don't have presently.

Is there any other device I can use to check apart from oscilloscope?
Swagatam said…
Hi Baasit, you can use your PC as an oscilloscope and use to confirm the waveform....download the free version of Goldwave software, and then you can use it with your PC.

for more info Google "how to use PC as oscilloscope using goldwave"
Sir, what capacitor value I have to put the output of the transformer for the 100% sine wave ???
baasit yusuf said…
Many Thanks mr swagatam, I'm grateful.
God bless you
Swagatam said…
you are welcome!!
Swagatam said…
Matt, you will have to experiment it using an oscilloscope....
One last question is what this circuit supports the correction of output voltage ??
Swagatam said…
It does not include an automatic correction but according to me it's not required since the PWM is supposed to take care of the output voltage and ensure a fixed 220V or 120V... unless the load is incompatible and draws abnormal amount of current.
Please i need more explanations on how you connected your mosfets to the transformer
Swagatam said…
please refer to the first diagram,

drain to transformer taps, source to ground, and gate to 10 ohm resistors.
Atinuke Funke said…
hi engineer, how can i replace d pot with a fixed resistor and do d calculation of d right value because the pot needs to be adjust and readjust atimes. also most of d factory made inverters have no pot. thanks.
Atinuke Funke said…
pls, how can 7812ic work with 12v input.
Swagatam said…
Hi Atinuke, I have already answered your question yesterday under some other post, please refer to your previous comments...
Swagatam said…
output will be slightly less than 12V
salman usman said…
Hi Swagatam i tried this circuit and i get the out put wave form the same with the one that you design in fist diagram, i tried my best to filter it but is denied it still square wave. so can i do. thanks
Atinuke Funke said…
pls sir, any simple circuit to use 555ic to generate slow and fast triangle waves. i got a circuit online that produces square wave and triangle wave using one 555ic at 200hz.
Swagatam said…
Hi Salman, that cannot happen, I think your PWM circuit is not working.

please check the waveform at the base of the NPN/PNP BJTs and let me know..
Swagatam said…
Atinuke, all IC 555 astable will give you triangle waves across their capacitor...the frequency will depend on the capacitor value and the associated resistor value.
salman usman said…
Hello Swagatam thanks for the respond on my comment. I want you to know i substitute that 555ic and 2NPN JBT with SG3524 by using 2 internal transistors of SG3524 i connect them common emitter configuration and i generate 200hz, it work OK and i connect the out put to that gate driver(npn,pnp/npn,pnp) and i generate 50hz using SG3525 finally i get this sample of wave form. i sent it to your e-mal thanks
Swagatam said…
thanks salman, I have not yet checked my emails, I'll check it soon and let you know...
salman usman said…
Hi Swagatam i am wetting for you, pleace
Swagatam said…
Hi salman, you will see it posted within the next two days...
Swagatam said…
sorry please ignore the previous answer, It was in response to an earlier request regarding a full-bridge SG3535 circuit....

as for your question please send it again to my email I'll try to check it out and solve it.
DareDiamond said…
Please Sir, may I know if I can get 80khz 6kVAC Pure or Modified sine wave output from this Circuit?

I need the high voltage to to drive 12 500g serially connected coils of 180ohms each.

Swagatam said…
yes you can get the mentioned output from the above design, but the transformer will need to be a ferrite cored
Ram Patil said…
Hi Sir,
Can you suggest me design for 24 volt 1220 watt, 2 kW and 5 kW Solar Inverter design please... Also what will be the basic design change if wattage increases like 1.2 KW, 2KW & 5 KW...

Swagatam said…
Hi Ram, you can refer to the following article


you can use it for all the versions that may be below 5kva.....make sure to use mosfets rated to handle the specified amount of load current
Abduleng Aminu said…
Sir is that really pure sine wave
Swagatam said…
Aminu, yes it can be a pure sinewave if optimized adequately
The circuit seems working but how come you did a voltage control .I explain if the no load output find yourself a 260 volts I also have more 'but that tends to fall with the load, but if you have a control of output voltage always you have a stable voltage
Abhishek Sharma said…
Hi swagatam sir, can I give above circuit input from astable multivibrator circuit, if I do it, what wave form will I get as output, I'm not familiar to use ICs.
Swagatam said…
Hi Abhishek, the frequency input to the transistor stage can be from any suitable source, you will always get a sine wave at the output, so you can replace the SG3525 with an astable of your choice and still get a sine wave
Thank you Mr. Swagatam and I appreciate your great work and efforts. I need to clarify more about the value of resistors which feed the MOSFETS. As per the given diagram, it's 10E. Can you clarify more about it please as it's not really clear enough.

Thank you.
Arvind Kumar said…
hi Swagatam! greetings!! I felt very glad to read your blog out here and the manner in which you responded to various queries/ clarifications raised by electronics hobbyists/ enthusiasts. I am also curious to know whether this inverter can be configured to obtain pure sine wave at 400 Hz? Why I am asking is because I am associated with Aircraft systems, and as you know they work with 115V, 400 Hz AC. Thanks. Arvind K (Bangalore)
Swagatam said…
You are welcome Mohammed, the values are 10 ohm each, please click on the diagram to enlarge it and view the details clearly.

10E refers to 10 Ohm
Swagatam said…
Thank you Arvind, I appreciate your thoughts very much!

yes the above circuit could be also run with a 400Hz frequency simply by modifying the relevant R/C parts associated with the IC

However I am not sure what kind of core would suit for the transformer at 400Hz frequency, this you may have to confirm this with an expert transformer designer
Arvind Kumar said…
Thanks Swagatam!
What is better - to vary R or C, in terms of avoiding noise, if any.
Swagatam said…
Hi arvind, you can change any one of them or both, it may not be relevant to performance issues, the product of the two parameters basically become responsible for the frequency change only
Swagatam said…
Hello, did you check the output voltage of the inverter while your freezer is connected? if not please check it and also check the current by connecting an ammeter in series with the battery positive....and let us know the results.
Swagatam said…
Hi, it's 100 Ampere, and your battery will be flat within 15 minutes and almost permanently damaged if it's a lead acid type.

the rule is drawing current at 1/10th of the battery AH...this will ensure maximum good health and long life for the battery...
Swagatam said…
OK, I think you answered your question yourself....at 23amps the inverter needs to be above 5kva, while your inverter is rated to handle just 2kva....you can try connecting another battery in parallel, together they must be able to satisfy the momentary 6000 watts by the freezer.
Swagatam said…
sorry, you mentioned 23 amps for the battery...so it needs to be multiplied by the battery voltage and not 236....

so your inverter might be OK, it's the battery which needs to be upgraded with higher AH.
iyiola semiu said…
Pls sir i need full circuit for that 200hz and 50hz opamp for inverter with the connection tnx.
Joe Adeoye said…
Thanks for the wonderful post sir, i have made 3524 inverter years ago and i'm using it, but it is a square wave inverter. I think it's time to upgrade it to a sine wave. Sir, i have plenty questions to ask concerning the PWM. I don't want to use IC555 for generating PWM, i would prefer to use the SWPM opamp method using IC741. From your article, you told us that, if we feed two traiangle wave into pin 2 and 3 of the IC741 which one's frequency needs to be faster than the other. Now, my question goes thus:

1. The triangle wave, the Hi and Lo state, is it +12v and 0v or +12v and -12v (assuming i'm using a 12v battery)?

2. Please, can you help me with circuit diagram how to generate triangle wave, i only know how to use IC555 to generate saw-tooth wave, but i have no idea how to generate perfect triangle wave. Please help?

3. What is the ratio of the frequency of "FAST TRIANGLE WAVE" to the "SLOW TRIANGLE WAVE"? is it ratio 1:2 (example: fast=200Hz while show=100Hz)

I joyfully await your response sir. :)
Swagatam said…
Thanks Joe, I am glad you liked it!

Here are the answers:

1) they just need to be +12V, and 0V

2) If you search online regarding how to generates true triangle wave, you might surely get many related options, you can give one of them a try and check, otherwise IC 555 can be also used in the astable mode (a couple of them), the saw-tooth won't cause any problems, it will still work as good as a triangle wave.

3) the ratio could be 1:6, this will give you six pillars for each SPWM waveform.
Adrees mohmand said…
Thanks a million Sir!
it's really helpfull but i have still confusion. i need 40% duty cycle from sg3525 but i get maximum 49% duty cycle. i have my own design of smps dc dc converter i-e 12vdc to 310vdc using etd40 ferrite core tranformer. for which i need 40% duty cycle. i am tried on searching but fail. please sir help me how can i get my goal. please
Adrees mohmand said…
Sir i have an idea in my mind. if i increase the dead time more and more, Is this decrease the pulse width.?
Swagatam said…
You are welcome Adrees, the pin#1 voltage determines the PWM ith reference to pin#2 of the IC, you can adjust the two levels and fix the PWM accordingly, for more info regarding the pinouts, you can read the following post

Swagatam said…
yes that's possible, you can try it...
Adrees mohmand said…
Pin#1 voltage is triangular wave or pure dc.?
Joe Adeoye said…
Sir, I am working on this PWM, first, I want to generate a saw-tooth wave using 555 timer, I joined pin 2,6,7 together and connected to V- with 1uF cap. The pin 2,6,7 is also connected to collector of Bc557 whose emitter is connected to V+ via 2.2k resistor and the base is connected to reverse voltage coming from 2v7 zener diode and grounded with 470 ohm resistor. Now, I placed the probe of my scope on the pin 2,6,7 which are connected, I got a saw-tooth wave as expected, but the problem is that, the bottom of the saw-tooth wave is not getting down to zero volt, I powered the circuit with 12v but the saw-tooth wave is between 8v and 3v, it is not getting down to zero volt. Can I feed this into an op amp? Will it work? And how can I make it come down to zero volt?

Thank you sir.
Swagatam said…
Joe, please try the 555 sawtooth circuit which is used in the following article, and see if it helps...

Joe Adeoye said…
Hahaha haha.... Worked Like charm.. You're a genius. The 555 IC in your diagram is wired in monostable mode which is triggered by pin 13 of 4047 IC, so, I used a separate 555 IC to trigger it, and it worked.... Clean saw-tooth wave on my scope. Let me continue with my work... ? ?
Swagatam said…
that's great joe...keep up the good work...
Anas Ahmad said…
hello good day, i didnt see your replies, hope am not disturbing, like i said am a novice
Swagatam said…
Hello Anas, I have transferred our discussion into this post, you can carry on the discussion under this article

jimoh tosin said…
Hello swagatam, pls. Can you show us the full diagram of this circuit you explain. Or send to my box. Tosine4anybody@yahoo.com . Tosin by name
Swagatam said…
Hello Jimoh, the full diagram is already provided at the bottom of the article, please click to enlarge it.
Ravindra Balme said…
hell sir thanks for sharing your knowledge with us.....i have made this circuit but i didn't get any output please suggest me what can be done??
Swagatam said…
Hello Ravindra, it would be difficult to troubleshoot your circuit because I cannot see what mistake you might have made in your.

I would suggest you to first learn all the basics and then build a simple SG3525 inverter, after that you can go for the PWM integration as instructed in the above article.
Thanks Swag for your devotion and dedication ...

Some few follow up questions,
-How will i know that the adjustments i Have made with the pot of the pwm are optimal?
-I thought this circuit was an ultimate pure sine wave inveter schematic, after reading your reply to this comment I was deviated from what I knew, My question is thus,
Which filtration need to be added at the output to make the output similar to the pure sine wave?
For Knowledge's sake, How do I wind the Inductor coil? The spacing, Henry measurements, length etc?

very new to me.
In fact i don't know why BJT stage should be close to the mosfet gate, May I know why Please.
Swagatam said…
Buberwa, it is the ultimate sinewave circuit because it is easiest and the most effective design according to me.

PWM must be set until the output of the transformer shows 220V or reaches the required correct output voltage level.

initially you can add a 0.22uF/400V capacitor and check its response on oscilloscope.

do all these only if you are well versed with all the basics of electronic..otherwise please do not attempt this circuit.
Swagatam said…
you can ignore the inductor, it's not required..or you can buy it readymade.
Anthony Ekoe said…
I build this circuit with difficulties,and I ended up getting 225volts but output frequency was 150hz and fluctuating down continually not stable. My Major problem was Ne555 p.w.m circuit finding the 200hz.I finally had by try and error way.So Mr Swagatam, please help me find it easily by giving me the exact values of the two capacitors in pin5,pin 2&6, of ne555 or help solve the problem. Operation sound rough.thanks God your blog.
Swagatam said…
you can build any SG3525 circuit, and integrate it with the PWM, it is not necessary to build the one which is shown in the 4rth diagram fro top.

200Hz is also not a mandatory figure, it can be 300 Hz or 400Hz also, 200Hz was chosen to keep the harmonics at minimum.

Pin#5 capacitor is always 10nF, pin#6/2 capacitors can also any arbitrarily selected value, such as 1uF/25V...the other values can be adjusted by using the following software (second option on the page)


the 150Hz reading is incorrectly shown by your meter, it's probably the PWM frequency which is being caught by the meter, using an oscilloscope to check the exact frequencies.

drahcir _26 said…
Master if i slow down the pwm to 300hz the waveform chopped into 4 times, and the voltage drop form 220vac to 140vac with the load of 40watts soldering iron. i think if we use this pwm method on h-bridge orientation this will reduce the quality vs efficiency.
Swagatam said…
Hello, the voltage drop may happen due to the following reasons:

incorrect PWM duty cycle
insufficient transformer, battery current output.
you can correct the issue by connecting an ammeter in series with the battery, and then adjust the duty cycle of the PWM until the optimal current is reached and the voltage is raised upto the desired limit.

basically insufficient current from battery or insufficient trafo saturation is main factor that leads to voltage drop
Swagatam said…
pwm has nothing to do with efficiency..we are using PWM here just to "soften" the square wave DC output in terms of correctly regulated RMS value, so that it can reach close to the sine RMS value
drahcir _26 said…
so why theres no voltage drop when i disconnect the pwm to chop the waveform? i will try to measure the ampere next time i will update you soon, and i try to change the load with 40w incandescent bulb. maybe my analog multitester confuse on monitoring the current voltages.
Swagatam said…
it's because chopping is cutting out the sections from the original square wave leading to reduction in current... this has to be compensated by using higher current winding at the primary side so that the winding can absorb optimal current from the high sections of the chopped waveform.
drahcir _26 said…
this is my current inverter. master pls help me how to incorporate with you pwm method on this circuit, my english is poor pls understand.
Swagatam said…
you just have to replace the mosfet section of your inverter with the first diagram as shown in the above article.
Joe Adeoye said…
Also, do not use IC741 OP-amp because it requires positive and negative voltage to power it. You can use LM324 or 358 which can be powered using a single source
Swagatam said…
Hi Joe, I accidentally deleted your previous comment, but fortunately I had the copy saved in my email, so I am copy pasting it below for benefiting the other readers:
Swagatam said…
Advise from Mr. Joe

Good day drahcir, I have been in your shoes before suffering from voltage drop problem after introducing PWM to the square wave from 3524 IC. It took me weeks for me to be able to figure out and resolve the problem. The problem i had then is that, using a normal square wave, after connecting load, the voltage still remains at 220v which is pretty good. But when PWM is introduced, whenever i connect load of 60Watt, the voltage drop by 50% i.e. from 220v to around 110v. Taking time to understand what is going on helped me to resolve this problem. First thing you need to understand is how the PWM works, when pwm is not introduced to your square wave, you have your FET turned on for 20ms and off for 20ms (if working with 50Hz) which in turns gives you the desired output. Now, when pwm is introduced, like for example, using 200Hz pwm which divides your square wave into 4 segment, you notice that the ON and OFF time has been reduced by 50% i.e. dividing 50Hz into 4 pulses, you have 2.5ms ON and 2.5ms OFF for 4 times, adding 2.5ms * 4 gives you 10ms ON and 10ms OFF, which originally was 20ms, which will cause your output voltage to drop by 50%. This is why it is always recommended to use a 6-0-6 traffo for 12v power supply, or 12-0-12 traffo for 24v power supply which will help you get your full output voltage.

Now, concerning the voltage drop, from my experience, the filter i was using is causing the problem. Normally, after applying PWM, you need some filter at the output of the traffo in order to filter out harmonics, if no filter is used, you'll get some funny readings from your scope and endanger loads connected to traffo output. In my case, i was using 1uf/400V capacitor as filter. After adjusting the pwm POT, i got a clean sine wave from my scope at desired voltage but when i connect load of 60W soldering iron, voltage drops to 120V. The problem there was that, the filter i used was deceiving me, i.e. giving me wrong voltage readings on my multimeter. After setting the PWM POT and getting a clean sine wave, i removed the filter and check the voltage on my multimeter and i discovered that it was around 190V, and when i add the filter again, it jumps up to 240V which was a *FAKE voltage.

So, the thing is, i wasn't really getting the voltage i thought i was getting as output voltage and which is why the voltage dropped at high rate, because, powering a 220V load with 190V source, leads to insufficient voltage and in other to complement the voltage, it will draw huge amount of current which will also reduce the voltage the more.

I have tried several PWM with no success, i am ALWAYS faced with this same challenge.

One day, i came across another PWM circuit on this blog which saved my life. If you scroll up, you will see another PWM circuit, using Operational Amplifier (OPAMP), to generate SPWM, all you need to do is know how to generate a triangle wave which is quite simple, generate a fast and slow triangle wave and feed them to the input of an Op-amp, and it will give you some sort of SPWM which you can use. Note that the *slow triangle wave form must be 2 times your original frequency e.g. 50Hz for 100Hz triangle wave. And the *fast triangle wave shouldn't be less than 2KHz, otherwise, your output sine wave won't be *pure. As for me, i used IC 4047 and i used the PIN 13 to generate the triangle wave for the *slow wave fed into op-amp. This gives me 100% accuracy on the TIMING.

So, to summarize the whole story:
1. Check your output voltage when you remove your output filter
2. Connect a little load (like a soldering iron) without filter and read the voltage again
3. Connect your filter and read the voltage
4. With filter connected, connect your load and measure the output voltage again.

As for me, the SPWM circuit saved my life and working pretty fine using 2.2uf/400V cap as filter.

WARNING: Do NOT connect any surfisticated electronics as load. Always use something like a soldering iron as load during test.
Swagatam said…
you can refer to the following article for the details

rynyahu fausto said…
Hi...mr. swagatam appreciate your goid works hobys electronics i like those simple sinewave generation of inverter is it posible to simulate the circuit before i attemp to build im trying using proteus but not working only the pwm 555 side working but sg3525 configuration not work im using sg2525 proteus model what simulator you use to simulate the circuit?
rynyahu fausto said…
Hello mr. Swagatam i try to simulate the complete circuit using proteus but dosent work only pwm 555 working sg3525 in output trabsformer not work im using sg2525 proteus model
Swagatam said…
Helo rynyahu, that's the reason I never use software for testing any circuit, I prefer simulating the design inmy brain and then implement it practically...if you are really interested to succeed with any electronic then you must first understand the design from the core and then build it practically using good quality parts.

If You are depending on a software you would be wasting your time.

or alternatively you can try applying any other SG3525 circuit from the internet and see if it responds in the software, there are many versions on the net.
drahcir _26 said…
MR. Joe Adeoye!you save my day! i am now totally understand why too much voltage drop when connected any pwm method to make the waveform similar to sinewave. now all i need to do is use OP-AMP as SPWM and use 6-0-6 transformer.

MASTER SWAGATAM! can i use ic556 to generate both slow and fast triangle-wave?
Swagatam said…
Thanks Dracir, yes you can use a single IC 556 configuration and you can collect the two frequencies from across the two respective timing capacitors.

However, the type of PWM is not the culprit, it's the duty cycle adjustment that affects the output, so you

must understand how the PWM functions and how it must be optimized to get the correct

results from it.

without PWM the duty cycle is 50%, therefore if you multiply the battery 12V with this 50%

you get 6V, multiply this 6 with the current consumption, say for example 10 amps (for a

10amp/0-12V trafo), you get 60 watt as the answer, for both the halves this becomes 60 + 60 = 120 watts, that's exactly what your rafo is rated, therefore you are able to get full output.

suppose you are using a PWM 50% duty cycle, and you apply it to the gates of the mosfets, this will cut the already present 50% duty cycle further down to 25%, therefore your output will become 60 watts instead of 120 watts.

Therefore it's not the type of PWM that matters rather it's how you optimize it makes the difference.

rynyahu fausto said…
hello swagatam thanks for the reply mr. is the pwm circuit will work for all square wave inverter i have a square wave made myself i plan to use your pwm circuit only using those BJT buffer stage mosfet driver stage
Swagatam said…
hello rynyahu, yes it will for all and any square wave inverter..you can easily customize the first design above with your specific inverter
rynyahu fausto said…
Ok thanks swag...one more thing is this circuit can be added to any squarewave inverter to modify as closes to main ac sine wave without any isue? I plan to add this circuit to my square wave inverter
Swagatam said…
yes that's possible
rynyahu fausto said…
Shalom to you sir swagatam thank for a kind reply my another question is why the sg3525 circuit as shown above has not implemented with a feedback circuit for stablization of the output voltage lets say a 220vac should be stable during load or even at its maximum power of load the output voltage will be regulated or corrected
Swagatam said…
Shalom rynyahu, the automatic output voltage regulation is an optional feature which is not crucial, because if the inverter trafo is selected correctly its output will never exceed 250V, which any load can handle with comfort.
rynyahu fausto said…
shalom sir swagatam thank you for the information i appreciate your good work for helping everybody needs
rynyahu fausto said…
shalom sir swag you mean if my supply voltage to the inverter circuit is 12VDC the transformer to use will be like 9-0-9 center tap since it is pushpull or if my supply voltage is at 24VDC my trafo should be at 18-0-18 center tap am i correct? at this point feedback circuit is not crucial at all handing the load without dropping the output voltage?
Swagatam said…
Shalom Rynyahu, you are right, keep the trafo input winding value almost close to the battery value for getting a correctly optimized output mains, but this may be true only for non PWM circuits, for PWM circuits the trafo voltage rating should be much lower than the battery value, and here the PWM should be adjusted for the setting up the correct output level.
Anthony Ekoe said…
Hello Mr Swagatam, I am at my wit end just the fact that I am not a skill type in electronic.Your circuit sg3525 pure sine wave, am still unable to get my 50hz frequency having done all I could with my little Automobile electric knowledge. Dear designer, inventor and public mentor, I wish to bring on your table an old power inverter circuit for your clarification, this I built several time. But it has very small output, since I began browsing through internet it has been my wish to build something more sophisticated.
My circuit consists 3 integrated circuit. A regulator 7805 battery power source feeding NE555.And output pin #3 of ne555 connect output pin #3 of the third I.c SN7474.And from pin #2&6 and pin#5 of sn7474 is 2(22k ohms) one connected to earth and through a transistor 2N2222A through 2(820 ohms) to second transistor BD136 and finally through a 33 ohms 5 watts and 100 ohms to 2 power transistors 2N3055 to a transformer input. Please, how do I increase this to 1000 watts output and a pure sine wave? Please help I know you are not waery of our long bothering questions. My dear to you my engineer.
Swagatam said…
Hello Anthony, since I cannot see the schematic design of your inverter, it will be difficult for me to judge its internal functions and other related parameters, however power output of any inverter can be quite simply increased by adding more number of power devices in parallel at the output stage, ideally using mosfets, and along with this the transformer and the battery must also be proportionately upgraded to enable the power boost.

in your case it seems 2N3055 are used, which I am afraid doesn't look be an appropriate candidate for enhancing power upto 1kva even if more number were added in parallel.

you must select a mosfet based design for implementing the suggested upgrade, or replace the 2n3055 with mosfets, so that these can be added in parallel for achieving the intended output level, not forgetting the trafo and battery specs
Swagatam said…
Hi Drahcir, in one of your recent comments you asked whether an SPWM would overheat the mosfets or not, the answer is no, it won't if you use the BJT buffer stage as indicated in the above article, and if you keep the PWM frequency low, meaning use just 3 to 4 pillars for the SPWM , this will keep the harmonics within limits and prevent the mosfets from getting hot.
Swagatam said…
Hi Abhishek, a transformer will get damaged only if it gets too hot and burns, there's no other way a transformer can get damaged...I think your meter is faulty, and malfunctioning
Hello sir, I have checked multimeter with mains and it's showing 220v and 217v which is fine, are you sure the reason you mentioned are only to get transformer damaged and not the other reason ?Both The transformer never heated
And both inverters can't be false I'm feeling right now tired man, please read previous comments for more problems details this is first time in life I'm facing so much of problem in making something. Please help and don't get angry.
Swagatam said…
Hi Abhishek, I am sure of that, before a transformer gets damaged it will emit smoke or at least emit a burning smell...even burnt trafos keep working until the winding is completely shorted...if you proceed with proper understanding and follow my instructions then I will surely keep helping otherwise I may lose interest....

if you are tired then you must quit electronics and stop pursuing electronics....
Hi sir, ok I will follow your advice now tell me what is solution of my problems instead of buying new transformer what can I do if get 400v output should I use voltage correction circuit and are you sure voltage correction with that circuit will be best solution and not cause any problems. Please reply till night so that I could go to buy ic 741 from market.
Swagatam said…
Hi Abhishek, all my solutions were the best solutions but you did not follow them so far...that's the reason you are still struggling with a simple inverter circuit.

Please note that I may not repeat what I have already explained you many times.

to get 400V you must use a lower voltage rated trafo than the battery voltage, but since you were not ready to buy a new trafo I suggested you to buy another battery and connect it in series with the existing battery, you did not do that, so please do whatever you may feel may correct, or you can read the links which I have already suggested you previously and advised you to first learn the concepts thoroughly and then move ahead....
hi sir , Currently I am not having voltage drop issue .please,And i dont want
400v(why i will wish for 400v i am already getting 600v) .From yesterday I am saying you that suddenly transformer started giving 500 to 600v.i have checked both of my inverters with same transformer and also with 5amp transformer result is almost same .AND EVEN WITHOUT PWM ALSO THIS IS HAPPENING.
Swagatam said…
Hello Abhishek,

I have already explained you many times, and this is the last time I would be explaining, please write it down on a paper:

1) adjust the PWM to reduce the output voltage (RMS) to 240V, if PWM is not use then you can use the 741 IC regulator circuit to drop it.

2) if PWM is used make sure to connect a 0.22uF/400V or 0.33uF/400V or any such suitable capacitor to bring down the output to 240V even without load.

3) with PWM connected, if you see output dropping to 170V or lower then that could be due to low trafo current spec.

to correct the above voltage drop issue you can read the following article thoroughly and act accordingly

Swagatam said…
correction 3) point:

with PWM connected, if you see output dropping to 170V or lower UNDER LOAD then that could be due to low trafo current spec.
OK sir,(1)I understood you mean to say the 600v output without using pwm is not transformer's fault and it is normal.(2)I need to regulate it using 741 ic. And with pwm ic 741 regulator is not needed. Is it all that you want to say? But earlier this was not happening.
I think transformer might be damaged.
Swagatam said…
600V is not OK, it should be 310V but previously it was showing lower reading so it seems your meter could be wrong, or the transformer could be originally of bad quality and might have got shorted because of some low quality winding....but normally a transformer can never get damaged without getting burned
Swagatam said…
put 220V AC from input 220V side and check the 12V side with meter (AC)

if it shows 12V with load (12V bulb) then your is OK

....connect 220V with a fuse in series and and take all the due precautions
Hello sir, I tested transformer and put probes from centre tap to one side it shows 12v
And then from centre tap to other side (again 12v) after that I measure potential difference between both sides it shows 24v check link for 30seconds testing video https://plus.google.com/+AbhishekSharmatechperson/posts/KsC4NdgBLiG you will let know my English
Swagatam said…
it means your transformer is good, the 600V reading in your meter is wrong, connect a 0.22uF/400V cap across the output of the trafo and check again, this might bring it down to 310V
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