From: Winfield Hill
Subject: Re: Simple adjustable 0 - 400V regulator, with flaw
Date: 18 Jan 2003 12:50:57 -0800
Organization: Rowland Institute
X-Newsreader: Direct Read News 4.20
Barry Lennox wrote...
> Winfield Hill wrote:
>>> Winfield Hill wrote ...
>>>> The Intersil HIP5600 is an adjustable three-terminal regulator
>>>> that can be thought of as a 500V version of the LM317. I've
>>>> used it in many of my lab instrument designs and found it to
>>>> be reliable and, like the LM317, an elegant design simplifier.
>> ... snip ...
>> Close, Harry, but that resistor is happy enough. Keep looking.
> Two possible solutions?
> a. Use a 1 watt 1k5 resistor in series with the pot. That will
> help take the "sting" out of the capacitor's charge.
Excellent. That's my first simple solution and no-one suggested
it before you, very good! Perhaps a bit more than 1.5k would be
required to insure the lion's shared of the discharge energy stayed
out of the pot when it's set to a small fraction of a turn. Maybe
10k, etc. The compromise in this solution is the mimimum output
voltage would be increased from 1.2V to 12V, etc., not too bad.
> b. Use a rotary 3 position switch, one end (fixed 300v) goes to the
> fixed resistor, the middle position goes to a 1 watt resistor, say
> 4k7 to ground; and the other (2-400v variable) end goes to the pot.
> Then, when switching from fixed to variable, you are forced to go
> through an intermediate position that simply dumps the capacitor's
Clumsy, but that should work. Thanks Barry!