On Sun, 15 Jan 2012 16:43:18 -0500, "Martin Riddle"
wrote:


"Jim Thompson" wrote
in message ...
Here you go...

http://analog-innovations.com/SED/Bi...ubSwitcher.pdf

I figure, if you had a mind to, you could add regulation by running
this dude in burst mode, by stopping the 555 via its RESETbar input.

Diode D7 prevents some really weird behavior from back conduction. If
there were a need to tighten up the efficiency, I'd replace it with
another P-channel, body in the opposite direction from MP1 (for lack
of finding a suitable transistor, modeled as a 0.3 Ohm device
extrapolated from my vast CMOS device library :-). Then I'd use a
comparator to make the drop like a near ideal diode as in...

http://analog-innovations.com/SED/Pe...rIsolation.pdf


Component values included!

Cheers



Of course: "design" by Spice fiddling.

John