This is slightly related to an earlier post. I am using a TL494 as a driver to a bridge, and then on to two power MOSFETs and a step up transformer to end up when rectified about 1000VDC. I located a simple circuit that seems to make the TL494 operate, and I am able to generate pluses from about 26 kHz to 384 kHz, as well as vary the pulse width down to about 200nS up to about half the entire cycle. So that part seems OK. From there it goes to a bridge made up of two pairs of NPN and PNP transistors. Taking the output from there we feed the gates of two MOSFET's directly, which are tied to a small transformer with two primaries which also connects directly. When I power up I get maybe 3-400 V for awhile, then it gets erratic, drops to zero, and then the MOSFETs get hot and either burn or cause some other catastrophic failure. I last used about 120kHz and 200ns pulse width and the scope, looking at the MOSFET gate input, shows clearly one firing then another with plenty of zero time in between so no overlap. (see below). I've tried 09N05's, IRLU024's and recently IRF540's. All should have had the capacity to handle the load. The transformer's dual primaries appear to be quadfiliar wound, and about .38 ohm each. The transformer has a ferrite core and was made for precisely this application in an identical configuration the only difference being the TL494's surrounding circuitry. I do not know what to vary or adjust at this point to make this work; clearly I am missing something.
Here's the MOSFET gate drive. Thanks for any comment or direction.
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