On Thu, 17 Dec 1998, Tjaart van der Walt wrote:

> I also have a similar question for the SMPS guru's. I've
> been asked to re-think a design where a PIC get its power
> from a 100V-150V DC line. How the hell does one drop
> around 90V DC without creating an oven? I don't want to
> use light bulbs as it is a potentially dangerous device.

You can try to build a small self-oscillating SMPS with 2 transistors and
a small ferrite core (pot + pot). Insulation will be a problem, and RFI is
something to think about imho. For 150V input you can use medium power
high voltage transistors designed for video amplifier duty.

If you do net need galvanic separation, then the transformer can be
replaced by a simple coil, although at this voltage ratio it does not look
like a good idea to me, at the first sight.

hope this helps,

Peter