Switcher PS temperature...

From: Paul Koning <pkoning_at_equallogic.com>
Date: Fri Jan 14 09:14:32 2005

>>>>> "Bill" == Bill Sudbrink <wh.sudbrink_at_verizon.net> writes:

 Bill> It's rated for 8 amps with no significant airflow (if I
 Bill> understand the specs correctly) so, I'm not even pushing it to
 Bill> its limit. Anyway, after about 10 minutes of operation with
 Bill> the case open and the new PS sitting off to one side (clear all
 Bill> around), the two heat sinks are too hot to touch. Is that
 Bill> normal operation for this kind of supply?


It makes sense for power supplies to get very noticeably warm at their
design load, because they are optimized for that load, and it is quite
acceptable for various parts (like the transformers) to heat up by 10
or 20 degrees at load. But if a heat sink is too hot to touch, that
means the transistors mounted on it are quite a lot hotter yet, which
means they won't last long.

One possibility is that the original design was correct for the stated
load, and then it was hacked up by butchers who wanted to trim down
the cost and didn't care that it invalidated the original design.
Apparently this happens. It was documented at length in a recent
article in either QST or QEX (U.S. amateur radio publications), in
which the author took one of those butchered supplies, reversed the
butchery, and redid some parts to make it a general purpose bench
supply. It's an excellent article, very well written if you want to
understand better how those supplies work.

Received on Fri Jan 14 2005 - 09:14:32 GMT

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