From: John Woodgate
Subject: Re: SMPS Topology Question
Date: Thu, 14 Nov 2002 20:41:11 +0000
Organization: JMWA Electronics Consultancy
Reply-To: John Woodgate
NNTP-Posting-Date: Thu, 14 Nov 2002 21:12:42 +0000 (UTC)
X-Newsreader: Turnpike (32) Version 4.01 <5Z8C9wtxbnpWyFnyfFzqmVF739>
I read in sci.electronics.design that james
wrote (in <firstname.lastname@example.org>) about 'SMPS
Topology Question', on Thu, 14 Nov 2002:
>I'm thinking about designing an offline SMPS to supply a voltage of
>400V at a peak current of 1A. This is for charging a large, high
>voltage capacitor bank for use with linear magnetic accelerators
>My question is: what topology to use?
>Since we are talking a peak power of 400W, should i be thinking of a
>forward converter or even half bridge or push pull?
>Anyone have any views on this or know of any resoureces that may help
>in this decision.
>thanks in advance
Forgive me, but I can't see why on earth you'd want to do that. Doesn't
a coil gun operate just as a one-shot device? So you have a relatively
LONG time to charge the cap. Even if you are on 120 V mains, a voltage-
doubler rectifier will give you 340 V just from the filter cap. You can
charge your big cap through a resistor at, say 100 mA or even less. It
just takes longer to charge. If it's 1000 uF, then at 0.1 A constant
current charge, it would take 340 x 0.001 = 0.34 coulomb to charge it,
which 100 mA supplies in 3.4 seconds. Of course, the current won't be
constant, but after 10 seconds the voltage will be within 5% of 340 V.
Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk
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