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Path: utzoo!utcs!lsuc!pesnta!hplabs!hp-pcd!john
From: john@hp-pcd.UUCP (john)
Newsgroups: net.micro
Subject: Re: Voltage protection for micros
Message-ID: <6200044@hp-pcd.UUCP>
Date: Sun, 10-Feb-85 13:34:00 EST
Article-I.D.: hp-pcd.6200044
Posted: Sun Feb 10 13:34:00 1985
Date-Received: Thu, 21-Feb-85 02:49:12 EST
References: <8296@brl-tgr.UUCP>
Organization: Hewlett-Packard - Corvallis, OR
Lines: 23
Nf-ID: #R:brl-tgr:-829600:hp-pcd:6200044:000:1018
Nf-From: hp-pcd!john    Feb 16 10:34:00 1985

<<<

   A good UPS does not come cheap because it is not a trivial task to generate
a high power 60 hz sine wave in phase with what the power company is no longer
supplying. Power supplies take a lot of stress between a varying source and a
unpredicable load and they need a wide stress margin to handle it.

   The annoying thing about UPS's is that after you go to all the trouble to
convert your battery power to 110 VAC is that the computer turns around and
converts it back to +-12 and +- 5 VDC to do most of the work. It would be a
lot simplier if computer power supplies were designed with a 12VDC inter-
mediate voltage that the user could attach to a Diehard for battery backup.

  This approach would be more expensive for the user who didn't want a battery
backup but a lot less expensive for those who did. As CMOS prices drop down
we may even see a move toward computers that require only 12VDC from a wall
transformer. A system like this would be easy to backup.


John Eaton
!hplabs!hp-pcd!john