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From: ih@udel.edu (Charlie Ih)
Newsgroups: sci.electronics
Subject: Re: How to make 600VDC from 800VDC
Keywords: high voltage, power supply
Message-ID: <33987@nigel.ee.udel.edu>
Date: 19 Oct 90 15:15:11 GMT
References: <92@decabo.enet.dec.com> <1990Oct18.134252.4635@mlb.semi.harris.com> <9510@milton.u.washington.edu>
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In article <9510@milton.u.washington.edu> whit@milton.u.washington.edu (John Whitmore) writes:
>
>It is also a good idea to put a collector resistor into the circuit; ....
>
>Also, power MOSFETs are available that can take the voltage drop this ...
>

John Whitmore made an execllent suggestion and good analysis.  This
is probably the most practical circuits to use.  However, if +, - 4%
regulation (~ 575 - 625v) can be tolerated, a simple resistor will do
the job.  On the other hand, if you want to be very fancy and are not
worried about costs and troubles, etc, a "switching" regulator can be
used, as indicated below.  This circuit is an overkill for this application.
It may become practical for a larger voltage drop or for applications
where the output needs to be changed (by changing R1, R2 and others).

Suggested circuit:
      800V+ --------------+------+
			  >      |
			 <       |
			  >      |
			  |    |-
			  |   ||
			  +---||
			  |    |-+
			  +-|<---+
			  |      |
			  |      +-^^^^------------------------+---600V+
			  >    /|                              |
			 <     /|-^^^--^^^+-----+----^^^^------|
			  >    /|     |   |     |   /| R1  R2  |
	      +--^^^^^----|           | ____/   |   /|-^^^-^^^-+
	      |           |     10v   |/ /\     |   /|    |    |
	      |           |     Zener |   |     |         |    |
	     ///          |           | /////   |         |   --- Capacitor
			  |           |         |         |   ---
			  |           |   +-----+         |    |
			  |           |   | 10v power     |  /////
			  | Reference | __+__   supply    |
			  |           +|     |------------
			  |-|          |_____|__   Comparator/switching
			    ||            |     |             circuit
			    ||----------- +   ////
			  +-|
			  |
			/////