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Filter design for SMPS - high noiseat output

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saurav_sdpl

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Filter design

I have designed a flyback smps with 1W output power 5V@1A
When i am applying a load of 250mA , it is generating high frequency noise of abt 200mV peak at 5V output.

I have used 10nF, 100nF ceramic capacitors at output but of no use.

How can i reduce the noise.
Also my transformer makes lot of noise, my feedback loop incorporates 1nF capacitor , has this something to do with loop stability.

Please suggest
 

Filter design

thats 4% ripple so not much good.

what frequency is the ripple?

how much caps have you put on the output?

have you allowed for the ripple current in the cap decision?

have you varnished your flyback core and windings to stop them buzzing.....they all buzz if not varnished......just use tape for quick do it.

what is esr of your output caps?

what does it do with no feedback components ?(oviously you need the divider feedback voltage)

is it continuous or discontinuous?

did you use slope compensation?
 

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