Re: flybacks & transformer leakage

"Adam. Seychell" wrote:

> Pooh Bear wrote:
>
> >
> > 2% is just sweet. My current design has 3% IIRC ( non interleaved though ).
> >
> >
> >
> > At that power level almost certainly.
> >
>
> Thanks for the reassurance. When I was doing calculations for the RDC
> snubber in order to clamp peak MOSFET Vds to 700V I get 1.2W dissipation
> in the resistor ! Is this typical for 25W offline supply ?

Not unsurprising.

Have you looked at a 200V TVS ? E.g. P6KE200. Gives an assured clamping voltage.

http://uk.farnell.com/jsp/endecaSearch/searchPage2.jsp?Ntk=gensearch&comSearch=true&select1=208174&paramSelectCount=5&showImages=true&st=parametricSelection&N=1005247+401&Ntt=p6ke&comSearch=true&Nto=tvs+&newSearch=true&paramSearch=true&st=parametricSelection&x=29&y=14



> How about the "two switch" discontinuous flyback ?
> http://www.edn.com/contents/images/47173.pdf

Too complex for 25W !


Graham


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