Path: utzoo!utgpu!watserv1!watmath!att!att!emory!swrinde!zaphod.mps.ohio-state.edu!rpi!sci.ccny.cuny.edu!phri!roy
From: roy@phri.nyu.edu (Roy Smith)
Newsgroups: sci.electronics
Subject: Re: How to make 600VDC from 800VDC
Message-ID: <1990Oct23.180241.12286@phri.nyu.edu>
Date: 23 Oct 90 18:02:41 GMT
References: <1990Oct18.134252.4635@mlb.semi.harris.com> <1990Oct23.151030.5176@engin.umich.edu>
Sender: news@phri.nyu.edu (News System)
Organization: Public Health Research Institute, New York City
Lines: 31

ssave@srvr1 (Shailendra Anant Save) writes:
->                         ____________
->                       1|            |3
->  +800V ________________|   7805     |______________+600V
->                        |____________|
->                              |2
->                              |
->                              |
->                              |
->                            __|__/
->                           / /\
->                            /  \    195V Zener
->                           /____\
->                              |
->                              |
->                             _|_
->                              _
->                              .
->[...] They have very good regulation and a good current capability (1 Amp.)

	Unfortunately, you're asking the poor little 7805 to withstand a
in-out voltage differential of 200V!  Even if it had a Vce,breakdown high
enough, you would still be asking it to dissapate 200W at 1A load.  All
this will do fry the 7805 about as fast as you can throw the power switch.

	What you really need is a 78H600 :-)
--
Roy Smith, Public Health Research Institute
455 First Avenue, New York, NY 10016
roy@alanine.phri.nyu.edu -OR- {att,cmcl2,rutgers,hombre}!phri!roy
"Arcane?  Did you say arcane?  It wouldn't be Unix if it wasn't arcane!"