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[Amps] How much electrolitic for a HV supply ?

To: amps@contesting.com
Subject: [Amps] How much electrolitic for a HV supply ?
From: Peter Chadwick <g3rzp@g3rzp.wanadoo.co.uk>
Reply-to: g3rzp@g3rzp.wanadoo.co.uk
Date: Thu, 27 Sep 2007 05:55:02 +0200 (CEST)
List-post: <mailto:amps@contesting.com>
Tom said:
>Actually the ESR of the AC source, the load resistance, and 
the rectifier type determine the ripple and dynamic 
regulation.<
But is the requirement ripple reduction, or the ability of the HV supply to 
hold up for short peaks?
The capacitor releases  0.5 .C.Ve2 (one half C times V squared) joules where V 
is the  drop in the HV. That's also equal to coulombs/sec, which is I times t.
So you can equate these to figure how much capacitance is needed for a given AC 
supply impedance and frequency for an amount of ripple. But if you're talking 
of allowing a different voltage drop over a 50 millisecond speech peak, you get 
a different answer, and that's where a big capacitor holds up better. It also 
can show up a lot better on a 2 tone test as the tones get closer together in 
frequency, although I think we all agree that a 2 tone test is not the be-all 
and end-all of test methods. But in terms of ripple, the bigger the ESR, the 
sooner you get to the stage of diminishing returns.
73
Peter G3RZP
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