27-06-2024, 09:03 PM
Well, I looked at the circuit and it's grand without driving the IRF740 FET. Then it oscillates during FET on time. The 4049AC is oscillating. It is decoupled at pins with 100 nF. Adding another 100 nF across the MPSA05 & 2N5401 driver pair helped. The little 11V AC transformer drops to about 8V AC. It's too small!
Also the ILD74 dual opto-coupler is really slow (even in data sheet). I've found some single opto-couplers that measure 1/2 the LED capacitance (Not found data yet), so I will try one of them and bigger 12V to 16V transformer for PSU and a dual PNP transistor Schmitt trigger (so output goes to zero) to drive my output driver. About 10V to 12V pulse is recommended and I'm only getting 8V. Though that's better than the original barely 4.5V drive .
Also the ILD74 dual opto-coupler is really slow (even in data sheet). I've found some single opto-couplers that measure 1/2 the LED capacitance (Not found data yet), so I will try one of them and bigger 12V to 16V transformer for PSU and a dual PNP transistor Schmitt trigger (so output goes to zero) to drive my output driver. About 10V to 12V pulse is recommended and I'm only getting 8V. Though that's better than the original barely 4.5V drive .
