Path: utzoo!utgpu!watserv1!watmath!att!att!bu.edu!rpi!zaphod.mps.ohio-state.edu!caen!news
From: ssave@srvr1 (Shailendra Anant Save)
Newsgroups: sci.electronics
Subject: Re: How to make 600VDC from 800VDC
Message-ID: <1990Oct23.151030.5176@engin.umich.edu>
Date: 23 Oct 90 15:10:30 GMT
References: <1990Oct18.134252.4635@mlb.semi.harris.com>
Sender: news@engin.umich.edu (CAEN Netnews)
Organization: The University of Michigan, Ann Arbor
Lines: 69

From article <1990Oct18.134252.4635@mlb.semi.harris.com>, by jws@thumper.mlb.semi.harris.com (James W. Swonger):
> 
>       800V+ --------------|------|
>                           |      |
>                           >      |
>    Limiting resistor ~   <       |
>    10K ohms (20mA base    >      |
>    drive, assume Hfe is   |    | /
>    >= 10.                 |    |/     TV flyback (horizontal
>                           +----|      output) 1500V BVceo  
>                           |    |\     at least 50W. Better to
>                          ---   | V    parallel a couple with 
>                           ^      |    emitter ballast resistors.
>                          /_\     |____________ 600V+
>                           |
>                           .
>                           . Stack of diodes with
>                           . breakdown ~ 600V
>                           |
>                          ---
>                           ^
>                          /_\
>                           |
>                         __|__
>                         /////
> 
>  




           The stack of diodes to total a breakdown of 600V, would be
a LOT of diodes, unless you mean zeners....

           Here is one I can think of :




                         ____________
                       1|            |3
  +800V ________________|   7805     |______________+600V
                        |____________|
                              |2
                              |
                              |
                              |
                            __|__/
                           / /\
                            /  \    195V Zener
                           /____\
                              |
                              |
                             _|_
                              _
                              .
                                       

        Note that here, the o/p will be Zener volatage plus the last
two digits of the 75XX series regulators. They have very good regulation
and a good current capability (1 Amp.)  The ground should be common 
on either side.  You can use 7508 and use 192V Zener etc... Use a good 
heat sink. Also any other good feature of the 75XX is that they have
thermal shutdown.  Cost is about $2 at the Rack. (Radio Shack)

                                            --Shailendra
					ssave@caen.engin.umich.edu
					The University of Michigan
				        	Ann Arbor.