Re: Cockroft Walton Voltage Multiplier (fwd)

["High Voltage list" <hvlist@xxxxxxxxxx>]

Original poster: <sroys@xxxxxxxxxxxxxxxxx>



---------- Forwarded message ----------
Date: Mon, 26 Sep 2005 08:44:56 -0700
From: Jim Lux <jimlux@xxxxxxxxxxxxx>
To: High Voltage list <hvlist@xxxxxxxxxx>
Subject: Re: Cockroft Walton Voltage Multiplier (fwd)

At 08:10 AM 9/26/2005, High Voltage list wrote:
>Original poster: <sroys@xxxxxxxxxxxxxxxxx>
>
>
>
>---------- Forwarded message ----------
>Date: Wed, 14 Sep 2005 21:10:40 +0200
>From: Finn Hammer <f-h@xxxx>
>To: High Voltage list <hvlist@xxxxxxxxxx>
>Subject: Cockroft Walton Voltage Multiplier
>
>all,
>
>I seem to have heard, that if a Cockroft Walton Voltage Multiplier is
>terminated into a large topload, and if this topload is discharged
>instantly, all the diodes will die.

Yep.. I've done it.

Draw a circuit diagram of a few stages, then put a short from top to 
ground. Note that the current from all those capacitors goes through the 
diodes, with only the parasitic L and series resistance of the diodes to 
limit it.

I should qualify the statement: not ALL the diodes die.  Just some of 
them.  I think some give up their last gasp earlier, and thereby save the rest.

>If this is true,why is that,  and is it possible to add current limiting
>resistors to the design, to avoid blowing the diodes.

Sure.. depends on the regulation you want.  Putting a R in series with the 
diode burns a bit of energy,  so the voltage will drop faster with load, 
and the ripple will be higher, but CW stacks are terrible anyway.

Jim