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Old 18th Jun 2020, 12:00 pm   #20
dave cox
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Join Date: Jan 2009
Location: Bristol, UK.
Posts: 2,059
Default Re: High voltage regulator circuit.

AFAIK, the above circuit can be turned into a 'foldback' limiter with just 1 more resistor!

Increase the sense resistor to 68R and connect a 62K resistor from Q2 base to GND.
With the output shorted, 10mA through the sense resistor gives 0.68V which will will turn on Q2.
At a 400V output, 100mA through the sense resistor will give 6.8V but this is divided by 1K/62K turning on Q2.

I didn't build it !
Nor did I sim, YMMV

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