RadioBanter - View Single Post - 13.8V high current power supply

May 8th 06, 05:27 PM posted to rec.radio.amateur.homebrew

wrote:
Hi all and thanks again for all the responses.

Well I had another 10 minutes to spare again today so took a different
secondary tapping to try to get more voltage headroom. Following that
tweak, I now have 25.5VDC available across the large electrolytics.
This is obviously plenty enough for 13.8VDC regulated; but is it now
*too* much to drop efficiently?
Thanks,
p.

It's more than ideal but there is no such thing as "too much" if you've
got an adequate supply of heat sinks and circulating air :-).

Is 25.5VDC measured at your "full load" current or at "no load"? If
that's what it is like under a typical load then you'll get about 50%
efficiency from a linear supply.

A switching step-down converter is possible but if that were an option
you wouldn't be where you are today.

The no-load voltage is irrelevant for power dissipation because with no
current there's no heat.

Tim.