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I've read as much as I can find on switchers, but I always come back
to one same problem.  Once it's going, an off-line switcher is
simple.  It's the getting going that's tough.  Especially in flyback
configuration.

I've looked up alot of infomation on the web, and read through the
switching powersupply design contest a year or more back in the
PICList archives.  Russell's design comes close to the optimal, but
not quite.

So, what I want to know is if anyone has come across a guide for
different kinds of switchers with a high efficiency at 170VDC input
and, say 25VDC output.  Preferably isolated and with an isolated
feedback path.

What I'd like to be able to design is a powersupply with several amps
output, 90VDC to 250VDC input, true pulse-width modulation (i.e.
constant frequency, variable width) via optocoupler for feedback,
using a flyback configureation, and an operating frequency in the
near MHZ for good "power/weight ratio" in the transformer.

Thanks,

- --Brendan

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