Les wrote:
These supplies are switching supplies, not linear. You should check
some of the draws, I think you will be surprised about how little some
of them draw (admittedly there are various design strengths out there.)
In general, a linear supply is about 20-35% efficient, meaning that a
450 watt supply would draw about 90 watts all the time. But these new
switchers are about double that or more, meaning that the supply will
draw somewhere between 20 and 50 watts. Moreover that draw will
basically be independent of the size of the ultimate supply, simply
existing to control the switcher itself, and not the drive current.
Technology exists in some forms of "buck control" that could boost the
on line efficiency further reducing the drain. Power stuff is evolving
even faster than much of the other technology, but is less glamorous, so
doesn't get as much of the press.
Regards,
Les H
Here's some more interesting information on power supplies. Note that
best efficiency is attained at/near maximum load. So a 500 watt supply
looks good but may not be what you want when considering power
consumption and disposing of waste heat.
http://services.google.com/blog_resources/PSU_white_paper.pdf
Bob Goodwin
