Electrical – Need to generate PWM for sine wave inverter without using microcontroller


I tried a lot but the output wave is coming as pulsating square wave.
And I didn't want to include microcontroller in my circuit.enter image description here

I am attaching my circuit for reference of inverter using IGBTs.
I have generated PWM using schmidtt trigger ic (74ac14) and a delay opamp circuit.

Best Answer

No, no, and no, that H bridge will never work. If you have tried it you will find that on anything above a supply of a few tens of volts the lower IGBTs will now be dead.

Reason: to turn on the upper IGBTs you need to raise the gate voltage higher than the emitter and this means the gate voltage on the lower IGBTs will be a few hundred voltage above their emitter voltage (0 volts) and will be dead.

But wait, all is not lost, the Op-amp that drives the gates can never reach an output that is more than +15 volts and this saves the day. However, to make that H bridge work you need a drive level to the upper IGBTs that has a common mode voltage of the 300 volt supply rail.

Your circuit is pants and you need to really start from scratch and do some learning on H bridge drivers.

If you just want a logic level PWM signal that is modulated by an analogue signal then look to the LTC6992: -

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