From: John Woodgate
Subject: Re: V regulator input cap size?
Date: Tue, 22 Oct 2002 09:39:51 +0100
Organization: JMWA Electronics Consultancy
Reply-To: John Woodgate
NNTP-Posting-Date: Tue, 22 Oct 2002 09:27:35 +0000 (UTC)
X-Newsreader: Turnpike (32) Version 4.01 <5Z8C9wtxbnpWyFnyfFzqmVF739>
I read in sci.electronics.design that DaveC wrote (in
<0001HW.B9DA3AFA00342030163F7590@news.covad.net>) about 'V regulator
input cap size?', on Mon, 21 Oct 2002:
>How about a simple voltage divider across the 35vac liine? Say, divide such
>that one of the resistors has 20 volts across it. It won't be the example of
>efficient use of energy, but the circuit doesn't use more than about 300mA at
>Is this a do-able solution?
Well, sort of, but you get lots of heat. Is the 300 mA constant? If so,
you can simply put a resistor in series with the bridge rectifier, on
the AC side. This also changes the operation of the rectifier to more
nearly a current-fed type. You would need to drop 20 V at around 500 mA,
which is 40 ohms, 10 W. Not elegant, but possible.
Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk
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