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Flyback TOP261EN

Posted by: claudio avitabile on Tue, 10/12/2021

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.


Best regards 


Submitted by PI-MrScott on Wed, 10/13/2021

Hi Claudio,

Thank you for showing interest in Power Integrations and its products.
Can you share the schematic of your modified design and PI Expert's proposed schematic?
It will greatly help us in understanding the cause of your issue.

Thank you.