Kam Leo wrote:
On 10/1/07, Karl Larsen <k5di@xxxxxxxxxx> wrote:
Bob Goodwin wrote:
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
Hi Bob, I am interested in what Google has done but need a lot more
information. They say changing the PS to one making just plus 12 volts
will save energy. I do not see that as a given. In fact it makes me
think they are just passing on the voltage change to the mother-board
makers. I think the idea being the MB makers can make just the other
voltages their board needs. But converting 12 to 1.5 volts with economy
of power is complex and will jack up the MB cost somewhat, and will make
it hotter.
--
Karl F. Larsen, AKA K5DI
Linux User
#450462 http://counter.li.org.
They're trying to get rid of distributing AC to all the racks and the
losses resulting converting from AC to DC for each MB. If the MB
design only requires 12 VDC input then it is more efficient to have
only one AC to DC converter and buss the DC to all the boxes in a
rack. By the way, people have been bussing 24 and 48 VDC in equipment
racks for years.
The 12 volts can not be moved as 12 volts DC very far. The length of
a car is about it. So Google must have a lot of racks in close proximity.
--
Karl F. Larsen, AKA K5DI
Linux User
#450462 http://counter.li.org.
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