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Fly back SMPS, please evaluate.

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I have tried to make an fly back supply with input protection, EMI reduction for max 3.3V 1.5A
Every resistor is 1W, only missing parts is the resource electrolytes and maybe a inductor.

Is the design okay for a low loss, stable PSU?

A cursory look says the tl431 will be unstable as it lacks stabilising capacitor.
It’s a fairly basic design. I would use one of the dedicated smps chips. Why use a transistor. Mosfets are a better choice.
In the end you need to mock-up this circuit and see how it works. Perhaps run it through Spice as a preliminary check.

I fail to see the purpose of connecting the output capacitor to the TL431 and R9.
But that's only one of the dozens of problems I see.
Use a dedicated chip, this is really 1970s design.

Thanks for your help, I'll find a chip instead:-)

Are you building this for fun or for actual use?
If the latter, what's the reason for not using an off the shelf PSU brick?


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