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MOSFET's gets burnt

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  • MOSFET's gets burnt

    Please see the attached waveforms taken from oscilloscope. The pattern (A) shows the waveform of MOSFET's gates when the positive supply (12V) not connected to the push-pull transformer. When it is connected, the waveform (B) produces (too much noise/spikes) even the snubber is connected. After changing frequency from 36KHz to around 50KHz, waveform (C) appears which seems better but the MOSFET's gets very hot within one minute at 30% load. I changed the circuit with SG3525 (totem pole output) but the same result. So, the most suspected thing is transformer. changing the turns ratio or frequency slightly change the waveform. So, what is the solution?

    Note: The IC is TL494 (with frequency=about 36KHz)
    Attached Files