I tried to simulate a 400V flyback. I calculated and let it work at CCM mode but finally I got trouble with the stability, the mosfet drain to source spikes, and the mode issues. The mode looks like is working at DCM? spike appeared at drain seems too big! I picked the mosfet with 150V. The circuit I really want to make it work with Vin from 9 to 15VDC. The stability with low input voltage is awful.

My circuits is drawn in LTSPICE, see attached.

I also found the leak inductance resonate with some capacitance (where? capacitance from drain to source? or reflected Cout?), I even couldn't use damp circuit to get rid of it.... the Cout will be 2.2uF to 4.7uF but I copied a circuit found here to make simulation faster. I have to use the off shelf transformer. The transformer rating is Lpri=5uH, Lkk=0.1uH, 20A rating. 1:10.


lot's of trouble. Please help me. Thanks.........

 

tvs clamp saves the world! in stead of slow rcd clamp, I need to use tvs clamp on Lpri.