From: Jim Thompson
Subject: Re: A protection problem
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Date: Tue, 07 Jan 2003 23:27:37 GMT
NNTP-Posting-Date: Tue, 07 Jan 2003 18:27:37 EST
Organization: Cox Communications
On Tue, 7 Jan 2003 18:17:39 +0000 (UTC),
firstname.lastname@example.org (Ken Smith),
In Newsgroup: sci.electronics.design,
Entitled: "A protection problem",
Wrote the following:
|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?
How about a GTO (or a PMOS plus a diode) in series with the supply
output? Take feedback from cathode of GTO (or diode).
Positive voltages are blocked by the GTO (diode). Negative voltages,
use a sensing circuit to turn off the GTO if the output goes below
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice:(480)460-2350 | |
| Jim-T@analog_innovations.com Fax:(480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |
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