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From: "Frank Bemelman"
Subject: Re: A protection problem
Date: Tue, 7 Jan 2003 23:04:26 +0100
X-Newsreader: Microsoft Outlook Express 6.00.2800.1106
Organization: EuroNet Internet
NNTP-Posting-Date: 07 Jan 2003 22:08:11 GMT
"Ken Smith" schreef in bericht
> I'm currently working on a voltage regulator with a major protection
> problem. The specs are:
> Input voltage 23 to 28V. This is easy enough.
> Output voltage DAC controled 0 to 25V (doesn't need to boost make 25V when
> input is too low). This isn't too hard.
> Output current limited at 100mA. This isn't too hard.
> Some moron may hook a (+) or (-) 600V supply to the output. This 600V
> supply can supply a zillion amps so MOVs aren't the answer. PTC devices
> don't seem to be able to handle this case either.
> I'm tinkering with various active circuits but they all seem to end up
> with quite a few parts in them. Does anyone have an idea?
Since fuses are out of the question, it would have to something with
a relay that disconnect the 0-25 supply from its output terminals.
IOW, a circuit that uses a OVP, measures the current through the
OVP, triggers a flipflop and energizes the relay. The flipflop
can only be reset by removing the input power 23-28V.
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