I am using two PWM channels configured in complimentary mode. both of the channels follow the sinusoidal pattern as they should but when one of the channels is at the peak of sine wave, the lower channel is also on for a short period of time. [logic trace attached]
I am concerned if this type of PWM will generate a good sine wave from a half bridge?
If both transistors are on at the same time, you will experience disaster! Usually some "dead time" is inserted between the point where one transistor is switched off and the point where the opposite transistor is switched on. And vice versa.
If both transistors are on, you'll experience a spectacular "shoot through" as a conductive path between the supply and ground is established. In such moments, the current gradient is only limited by parasitic inductance - which is extremely small for any reasonable design.
Regards
Thanks U. adequate dead time has been inserted between complimentary transistors. I tried this on hardware and it worked.
resulting in a fundamental voltage output of 22 volts on 30 volts supply and a large component of third harmonic
Dear Muhammad,
I would like to welcome U. Dreher and than him for his valuable comments.
My question now:would you please tell us about the load at the out put. Is it an LCR circuit?
Please display the input and output waveform to comment on them. The configuration presented is not a classical half bridge inverter.
Best wishes
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