Hi, I used PI Expert to realize an AC-DC flyback converter, i followed the proposed schematic, but it didn't work, so I have modified the feedback net, and have placed some Zener diodes in series with TL431 (Vout is more than two times the Vka-max of TL431), I have removed the capacitance from ref pin of TL431, and increased value of resistance that limits current in the photodiode of optocoupler. When I switch on with no load, it works, still works if I increase load. But if I switch on the circuit after some time with my maximum load applied it goes to a output value much more low than the desidered Vout, about 28-30V, why? Have I to put a bleeder resistor on the output?
Device used:TOP261EN; Input: AC230V; Output: DC100V; Feedback Net: Optocoupler and TL431, with bias winding.