Simple PWM inverter circuit diagram using PWM chip SG3524

Here is a simple PWM dc to ac voltage inverter circuit based on IC SG 3524. The SG3524 IC chips is a fixed frequency PWM (Pulse Width Modulation) voltage regulator control circuit, with indifferent outputs for single ended or push pull applications. The SG3524 IC integrated circuit has all the functions necessary for the production of a regulating power supply, electrical inverter or switching regulator on a single chip.Moreover it can be used as the control element for high power output purposes. We know pulse width modulation PWM theory, i.e. a method of adjusting the width of the pulses in a pulse train relative to a control signal. If greater the control voltage, wider is the resultant pulses. Using a sinusoidal frequency as the control voltage for pulse width modulator circuits, it is likely to generate a high power waveform whose average voltage varies with the sine wave, which is suitable for driving ac loads.
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PWM chip SG3524 application notes

  • Regulating power supply.
  • Electrical inverter or switching regulator on a single chip.
  • Transformer-coupled dc-to-dc converters.
  • Transformer less voltage doublers, and polarity-converter applications employing fixed-frequency, pulse-width modulation (PWM) techniques.
  • The complementary output allows either single-ended or push-pull application. Each device includes an on-chip regulator, error amplifier, programmable oscillator, pulse-steering flip-flop, two uncommitted pass transistors, a high-gain comparator, current-limiting and shutdown circuitry.

Circuit schematic of PWM inverter

PWM inverter
Click on the circuit diagram for enlarged view

Components required

  1. Power supply (12 V)
  2. Resistors (10kΩ; 4.7kΩ x 2; 100kΩ x 2; 1kΩ, 1W x 3; 100Ω x 2; 20kΩ; 0.1Ω; 200kΩ,2W)
  3. Electrolytic capacitors (0.1µF x 2; 0.001µF; 1µF; 100µF)
  4. PWM chip IC3524
  5. Transformer (12-0-12 V primary, 220V secondary)

Working of PWM inverter circuit

  • The IC SG3524 operates at a fixed frequency, the oscillation frequency is determined by one timing resistor RT and one timing capacitor CT.
  • RT set up a constant charging current for CT. So there exists a linear ramp voltage at CT, which is connected to the comparator.
  • Comparator provides a linear control of the output pulse width (duration) by the error amplifier.
  • The SG3524 contains an inbuilt 5V regulator that supplies as a reference voltage, also providing the SG3524 internal regulator control circuitry.
  • The inside reference voltage is divided on the outside by a resistor network to give a reference to inbuilt error amplifier. (External reference can also be used).
  • The output is sensed by a subsequent resistor divider network and the error signal is amplified. This voltage is then compared with the linear voltage ramp at timing capacitor CT, thus producing a pulse width modulation (PWM) pulse.
  • The resultant PWM pulse from the comparator is passed to the corresponding output pass transistor (Q1, Q2 refer block diagram) using the pulse steering flip flop, which is synchronously toggled by the oscillator output.

SG3254 block diagram
 Internal block diagram of PWM chip SG3524

  • The oscillator output pulse also acts as an inhibiting pulse to make sure that both the transistors are never turned ON simultaneously. The duration of this pulse is determined by the value of CT.
  • The pin 11 and 14 are connected to the TIP transistor for driving the transformer. T1 is a 12-0-12 V primary, 220V secondary, 300VA transformer.
  • When signal at pin 14 is high, upper transistor is switched ON and current flows from the +12V source via the upper half of the transformer to the ground.
  • When 11 of the IC pin goes high, lower transistor gets switched ON and current flows from the +12V source via the lower half of the transformer primary and sinks to the ground.
  • Thus we got positive and negative half cycles of 220V AC supply.

Pinout of SG3524, TIP31A

67 thoughts on “Simple PWM inverter circuit diagram using PWM chip SG3524

  1. Hello. My group wanted to assemble your inverter project using SG3524.PWM. We purchased the parts but SB5200 was not available.
    Do you have any replacement for it? Would it be ok if we replace it with an ordinary rectifier diode with same voltage and current rating?

  2. What is the maximum power that can be generated. Is it possible to use this circuit to built a 1KVA inverter by changing the transformer

  3. Sir can i use 12 volt 100 amp battery with this circuit? is higher current of battery affect the circuit?
    i want 500w inverter by this circuit if i connect more mosfet in parallel and transformer changed then can this circuit work?

  4. good day sir, pls can i get some help on the calculations that made you choose the components. like why are you using 4.7kohms resistor at pin 2 and not any other value like 100kohms. thanks

    • Hi Damilola,
      It is the guide lines form the manufactures, you may please refer data sheet of PWM chip SG3524 for more information.

  5. hi.i wanted to know how to use this ic only as a pwm generator.i am making a project on speed control of ac motor using h bridge igbt inverter.but i want pwm signals and my professor suggested that i use this ic to generate the pwm pulses that are to be given to the gates of igbt.
    can you help?

  6. Hai,
    I have 3 no.s of 12 V 20 Ah sealed lead accid batteries with me, also a 300 W 230/12-0-12V transformer too…
    What much maximum power can i obtain from the most suitable configuration of these batteries with the transformer ?
    Which config. will give maximum power at 230 V. Parallel or series ?

    Can this inverter be used to operate sophisticated equipments like computers, laptops etc. ?

  7. can i use mosfet in this circuit instead of transistors if possible thn how … plz help me and can i control output voltage
    2. can i use 600va ups transformer

    • Hi Sanjed
      1. You can use MOSFET in place of transistor by rearrange the 100 resistors to the gate’s of the MOSFET
      2. To vary output voltage use taped transformer of vary the frequency.

  8. hello sir, good day..
    what software did you use to simulate the circuit?
    is there any replacement for the SG3524 if its not available???? thank you

  9. Hi admin, I’ope u r doing well. I’ve assembld ur invrtr crct, dat of sg3524. I used 2 mosfets irfz44, 12v 6.5ah, 12-0-12 5amp trnsfmr. I connected 2 cfl bulb and a small 12v dc fan to cool d mosfets. My problm is – the light only last for about an hour then goes up. If I connect it again it will light for about 5 min then goes up. Can you please help me fix it to light for about 5 hours? Thanks.

  10. hello sir.

    i want to make full bridge scr inverter based on pulse width modulation where 230 volt and 250 mw is at output. will u please tell me firing circuit for gate terminal in scr.

  11. Hi !

    I need to build higher ampere inverter with 36amps, 60hz output. Can I
    just change MOSFETs to IRF3205 and transformer rating to 40 amps to increase the load capability.
    Please suggest.

  12. Please, in what measurement ( AC or DC) should I set my Voltmeter if I want to measure the oscillator output from pin11 and pin14 of the inverter IC SG3524. When I set it to DC, the output is thesame ( ie 3.54V) on each pin, but when I set the voltmeter to AC, though, the reading ( ie 18.79V) is thesame on the two pins. Is the oscillator working well or not? I’m confusing, I was thinking the reading (18.79V AC) is too outrageous, help please.

  13. I need to convert a PWM Voltage 8 to 36V at 60 hz, Duty between 50 to 80 % and into a DC Voltage. The Load will draw upto 4A of current in this DC Line. Can you suggest how to do this please ?

  14. in my project i want to produce pwm from arduino , my question can i just move out the IC SG3524 from this board ?and i connected my pwm pin from arduino to the gate transistor,,, from my configuration can you tell me have the side effect or not to this board?

    please help ,tq

  15. I have constructed this circuit, but unfortunately I get 173vac output. Can you please help with tips of how to improve it to 220vac.

  16. HELLO,
    I built your circuit and i have 3v from pin 11 and 14 but the inverter does not respond. when i ground the transistor to the battery the initial reading on pin 11&14 return to 0. pls what could be the problem.
    you can reach me on

  17. hello sir i am construction 1000w inverter but in my circuit i use sd3524 the values resistors and capacitors i do,nt i need them sir thank u

  18. I would like to know the step involve in converting a circuit to CHIP. We have a circuit tested fine and OK. And we want to make chip of this circuit.

  19. I av being trying this circuit on livewire design software with my computer but it isn’t given
    me any voltage at the secondary output of the transformer

  20. sir by onnecting 60 watt bulb …my inveter output drops down to 90volt and the bulb light is also dim…..what is the problem…in my circuit

  21. Hi, I am interested to construct inverter circuit which will be driven by 3.6volt/7.2volt li-ion battery and give output 110v 0.65amp for charge my camera battery. pls help me to guide. I choose lioh battery due to low vol with high capacity.

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