the real circuit is the unknown here - as said above if there is significant wiring L - then there will be avalanche clamping losses as well as switching losses - thus 10oHz may be a limiting figure - also how is the fet heatsunk? none? some ...?
Tthank you for helping, I have now TLP250 MOSFET driver, but my power supply for this project is multi-output 12 and 5 Vdc,
and the ground is not isolated so the anode ground pin3 and GUD pin5 also the load will share the same ground.is that makes the microcontroller not isolated? or there is a solution to this problem without changing the power supply?