I have a PWM circuit that controls the RMS voltage to an incandescent bulb (actually 3 in parallel for testing) using PWM.
I'm testing with the following parameters. Vin=38V, Vout(rms)=14V, RMS current out = 29A. The load is switched by a pair of 75V D2Pak FETs on the low side. Switching frequency is ~244Hz.
My problem is the "inductive kick" when the FET shuts off. Voltage at the Drain shoots up to ~77V above the source pin for about 5.7uS then drops off to the Vin of 38V. I've tried adding a 2A Schottky diode across the load, but the voltage at the Drain still shoots up to ~77V for 4.2uS under the same input/output parameters.
Is there some sort of "special" diode I can look for? Or a diode with a certain spec? I've been looking for diodes with a fast Forward and Reverse recovery times.
Am I missing something?