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Old 21st Jul 2020, 4:27 pm   #52
Diabolical Artificer
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Join Date: Jul 2009
Location: Sleaford, Lincs. UK.
Posts: 7,633
Default Re: High voltage regulator circuit.

Well, i've built the circuit, but it doesn't work, Vop sits at around 30v and won't budge. I can't see how adjusting R2 changes Vgate. Is the circuit round R1, R5 Q7 right? As i read it the base of Q7 is fixed by R4/5 divider.

These are the changes and values i came up with, see attached schematic. As mentioned I've had no luck with TL431's so used a blue LED to give 2.5v. I3 I worked out should be 93.3k so used a 100k. At first I powered this up with a 35v PSU limited to 10mA to check that I'd made no connection mistakes. I used a 10k 10 turn pot, and did see some minor adjustment. When i powered it up to 400v I swopped this 10k pot for a fixed 150k and 100k pot, it being the nearest I have to 300k.

Andy.
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