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Old 21st Jul 2020, 10:58 am   #49
Diabolical Artificer
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Join Date: Jul 2009
Location: Sleaford, Lincs. UK.
Posts: 7,639
Default Re: High voltage regulator circuit.

Hi Dave, I'm breadboarding this circuit today, a few questions. Re V2, why does the base of Q6 have to be at 2.5v, and do I really have to use a TL431, I hate these bl**dy devices with a passion. The resistors are always ones I'll never have so far I calculated 1r and 3.119r with a 2k2 supply resistor, can't I just use a diode instead? A blue diode gives me 2.65v, then i can just tweek R6, yes?

Re D2, does that read 24v?

Re I3, that can just be a resistor yes? I've worked this out to 93.k, so could just use a preset and fixed R. I've sussed I4, I'm using a MJE350 CCS.

Lastly as i understand the circuit if Q5's base sees a change in current, Q6 will go the other way switching on Q4 harder (or softer)that changes V on the gate of the fet. Q2/Q7 regulate Vgs.

At present I'll run this at 100v, then when it's stopped smoking, crank Vin up.

Andy.
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