Date: Fri Nov 30 13:43:52 2007

Author: Bernard Cleyet

Subject: Re: Power Supplies - Switching vs. Linear

Yes that why some very high power supplies have motor driven variable
auto transformers (variac). This is good only, obviously, for slow
large changes, e.g. magnet P/S's.


Jason Alferness wrote:

> Dan Bernoulli wrote:
>> As another confusing consideration, I recall many "precision" power
>> supplies that had analog, i.e. linear front ends, then 40 kHz or so
>> switchers for the "fine" stabilization. Some of the high end HP
>> supplies from the 60(?)s worked that way. They were rock solid, could
>> anchor a battleship (rhetorically speaking) and were worth their
>> weight in gold (again rhetorically speaking). Its all in the
>> specifications. Regardless of the topology, better supplies cost more.
> Interesting... That seems backwards... I would have guessed that they
> would have a switcher course "front end" after the rectifier with a
> linear "fine" stabilization. Any idea why it was done that way? My
> thinking is the large voltage drop (from rectified ac) --> swticher to
> min power burned/wasted -- Linear dials in tighter with less heating
> effects, etc.
> 'Learn something new everyday...