Self oscillating and fairly simple, yes.
when you start adding power factor correction or special control functions
like soft start, a smps chip makes more sense. The trend in some new power
supplies is to actually use a microprocessor for control.
Microchip for one has been pushing their 32bit DSC chip for this:
http://www.microchip.com/stellent/id...ote= cn531747

Happy New Year all
Oppie (aka bob Oppenheimer)


"Tim Williams" wrote in message
...
I see circuits like these in VCRs a lot... not really anywhere else, for
some reason. Not the greatest efficiency, but the parts are a lot cheaper
than a whole UC3842 or TL494 deal. Maybe not worthwhile against
TOPswitches and such these days.

Efficiency as shown is around 67%. Runs at ~200kHz full power, much
slower at lighter loadings (it fires a full cycle, then stays off for a
while)

Tim

--
Deep Friar: a very philosophical monk.
Website: http://webpages.charter.net/dawill/tmoranwms