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Modifying a 4047 IC Inverter into Sine Wave Inverter

The post discuses how to modify an ordinary square wave inverter using IC 4047 into a modified sine wave inverter through PWM technology. The idea was requested by Mr. Philip

Technical Specifications

I hope that i am not going to be a bother, but I need some advice with a PWM-controlled modified sine wave inverter I am designing so I want to seek your expert opinion.

This simple design is tentative, I haven't implemented it yet but I would like you to take a look at it and tell me what you think.

Also I want you to help answer some questions which I have not been able to find answers to.

I have taken the liberty of attaching an image of a quasi-block diagram of my tentative design for your consideration.

Please help me out. In the diagram, the IC CD4047 in the inverter is responsible for generating square wave pulses at 50Hz which will be used to alternately switch on MOSFETS Q1 and Q2.

The PWM circuit will be based on IC NE555 and its output will be applied to the gate of Q3 so that Q3 will provide the PWM. Besides this, I have two questions.

First, can I use square waves for the PWM pulses? Second, what is the relationship between PWM frequency and supply frequency? What PWM frequency should I use for a 50Hz inverter output?

I hope that this design is feasible, I think it is feasible, but I want your expert opinion before I commit scarce resources to implement the design.

Looking forward to hearing from you sir!

Sincerely, Philip

simple IC 4047 inverter circuit

modifying IC 4047 inverter into pwm sinewave

Solving the Circuit Request

The configuration shown in the second figure would work but the addition of one more mosfet would unnecessarily increase cost and heat dissipation making the circuit sightly inefficient.

The PWM section should be built as explained in this article:

The PWM transforms the flat square waves into a modified square wave by chopping them into smaller calculated sections such that the overall RMS of the waveform becomes as close as possible to an actual sine counterpart, yet maintaining the peak level equal to the actual square wave input. The concept may be learned in details here:

However the above transformation does not help to eliminate the harmonics.

The PWM frequency will be always in the form of chopped square waves.

The PWM frequency is immaterial and may be of any high value, preferably in kHz.



Need Help? Please leave a comment, I'll get back soon with a reply!


  1. can this be setup as a H-bridge circuit so that I can use a 0-12v transformer?

  2. it's better to use special H bridge driver ICs instead of trying converting other ICs which could make things too complex.

  3. Thank you sir please how many voltage transformer should I use and for c1 that you say 22uf how many voltage? Thank you

  4. Basiru, if your battery is 12V, then you can use a 9-0-9v trafo....C1 can be a 22uF/25V cap.

  5. Good morning sir I didn't get the ic4047 can i use HCF4047BE?

  6. Sir I didn't get the ic cd4047 can I use hcf4047be?

  7. Hi Basiru, yes it will also work....

  8. Ok sir I have done it as you show me but I didn't get the output the only thing I see if I sparks the wire on battery the output will blink small,after that I didn't put the regulator because I don't know how to put it.and you didn't put it in the diagram, please sir I need more help,thank you and God bless you.

  9. adjust the preset to get the frequency working...

    what is the wattage of the trafo and what's the battery AH that you have used??

  10. Ok sir the battery is 12v 200ah and the transformer is 12v-0-12v 1000mA after that am experiencing difficulty in putting the 22k adjuster please help.

  11. and what was the load you used? with a 12V 1 amp trafo, the load cannot be more than a 6watt 220V lamp...anything bigger than this will not light up properly.

    if you want to illuminate a higher wattage bulb, you'll need to use a minimum 5amp transformer

  12. Good morning sir
    Please can I use 20k instead of 22k?

  13. Hi Basiru, you can use a 20k preset

  14. hello sir, how do you connect a protection diode do the drain of a MOSFET because I have been experiencing a problem of FETs blowing out?

  15. Hello Kakooza,

    connect 6A4 diode parallel to the drain/source, with cathode connecting with the drain, and anode to the source.

    also connect a 1N4148 diode parallel with the gate resistors of the mofstes...cathode towards the IC, and anode towards the mosfet gate

  16. Hello possible Sine Wave inverter 500w small circle with the efficiency of Aley low cost

  17. Dear Mr. Swagatan! Thanks for the good job. My question is how can use IC CD4047 to configure 500w transformerless inverter?

  18. Thanks Mansur, for implementing a transformerless inverter you will require a full-bridge circuit using specialized full bridge driver ICs, IC 4047 cannot be used


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