Ian White GM3SEK wrote:
RFI-EMI-GUY wrote:

There is a company that builds high voltage switchers for amateur
radio amplifiers, and there have been construction articles to build
these. (Check QEX magazine).

Regrettably the author of the key article, and owner of the company
"Watts Unlimited", died a few years ago.

The commercial unit followed some years after the QEX article. It
contained a number of important improvements but schematics were never
published. The big unanswered question is why that design had no voltage
feedback, and therefore had quite poor output regulation? (We can only
speculate that a feedback loop must surely have been tried, but proved
unworkable... and then wonder why that should be?)
(snip)

I worked on a 13.8 Volt SMPS made by TODD for Motorola as an OEM without
any documentation. There was a large stud mounted 13.8 Volt zener on the
output to clamp the voltage and some op amp circuitry to sense if the
output voltage fell below 13.8V it would start increasing the PWM to
charge the filter caps. This PS apparently never worked right because
the transformer leads were never soldered and then were plastered in
conformal coating.


--
Joe Leikhim K4SAT
"The RFI-EMI-GUY"©

"Treason doth never prosper: what's the reason?
For if it prosper, none dare call it treason."

"Follow The Money" ;-P