Xref: utzoo comp.periphs:1339 sci.electronics:4463
Path: utzoo!attcan!uunet!sco!rosso
From: rosso@sco.COM (Ross Oliver)
Newsgroups: comp.periphs,sci.electronics
Subject: Computer uninterruptable power supply
Message-ID: <1167@viscous>
Date: 9 Dec 88 08:43:53 GMT
Reply-To: rosso@sco.COM (Ross Oliver)
Distribution: na
Organization: SCO Technical Support
Lines: 27

I have recently been looking at uninterruptable power supplies
(UPS) for my microcomputer.  It runs UNIX, and is up 24 hours
a day.  All the UPS's I have seen are of the same basic design:
they take 120-volt line current, and transform it down to
somewhere around 12 volts to charge batteries.  While the power
is on, the 120 volts is also fed to your computer.  When the
power goes out, the UPS cuts over to battery power.  The 12
volt battery voltage is boosted back up to 120 volts to be
fed into the computer, where it is transformed back down to
5-12 volts to run the computer's electronics.  As I understand
it, some very complex circuitry is required to convert 12 volts
DC to 120 volts AC with a clean enough sine wave for the computer's
power supply to function properly.  This is one of the reasons
that UPS's are so expensive.

It seems to me that it would be much easier and more efficient
to move the batteries between the computer's power supply
and the computer itself.  This would eliminate the wasteful
transformer and costly translation circuitry.  It would also
reduce or eliminate the switching time (the time between when
utility power is lost and battery power kicks in).  Does anyone
know of a commercial UPS that works in this way?  Has anyone
experimented with this possibility?  Are there any micros that
have this capability built-in?

Ross Oliver
uunet!sco!rosso