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Path: utzoo!watmath!clyde!cbosgd!ihnp4!alberta!dyck
From: dyck@alberta.UUCP (Terry Dyck)
Newsgroups: net.micro
Subject: Re: Uninterruptible power supplies
Message-ID: <418@alberta.UUCP>
Date: Tue, 26-Feb-85 20:40:23 EST
Article-I.D.: alberta.418
Posted: Tue Feb 26 20:40:23 1985
Date-Received: Fri, 1-Mar-85 07:53:37 EST
References: <362@abnji.UUCP>
Organization: U. of Alberta, Edmonton, AB
Lines: 23


	On the low voltage input power supplies, why not put a diode
in series with the batteries. They won't charge from the AC supply,
but will always be on line if the power 'browns out' or quits. Because
they are right after the rectifiers they will only feed power into the circuit
when the voltage of the batteries exceeds the voltage of the rectifier 
output.

	There is a problem using a cheap 12 volt inverter. They put out
a square wave. The duty cycle of the ac is about 50% and this will
sometimescause overheating and very poor efficiency in devices with
a transformer input. There is also a problem of the very high
noise associated with square waves. From experience I know this can
cause very strange disk errors.     

	I would think you would be better off using the battery
approach mentioned. It would be more efficient, generate no noise,
and with a diode isolator, no problem using any type of charger 
you require.

				Terry Dyck
				U. of Alberta
				ihnp4!alberta!dyck