More snubbing
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SNUBBER
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The initial mosfet board saw a huge inductive back emf HV spike that was clamped to ~75v by the mosfet body diodes,but the energy dissipated would get bigger as the weld duration went up, eventually causing mosfet failure. Adding the snubber buss and schottky diodes did a nice job of limiting that HV pulse energy, which made the back emf pulse width a constant. The oscillation issue was caused by HF feedback getting into the gate drive buss,due to the parallel pc board traces and this caused the mosfet board to ring after it was supposed to turn off.
I added ferrite beads in series with the 10 ohmto suppress the oscillations, and as the traces show, that seems to be working.
The last thing to do is to get the High current charger circuit working, so my pulse frequency can be increased.
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