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WA2ISE > TECH 04.04.21 00:41l 12 Lines 1121 Bytes #999 (0) @ WW
BID : 21075_AL0Y
Read: GUEST
Subj: High voltage (~200VDC) bench supply with shut-off bleeder
Path: IW8PGT<IZ3LSV<I3XTY<I0OJJ<GB7CIP<CT7AXA<CT1EBQ<W0ARP<AL0Y
Sent: 210403/2236Z 21075@AL0Y.#NNJ.NJ.USA.NOAM LinBPQ6.0.21
As many of us, I built a high voltage (160V or so, 300ma) bench power supply. One hazard is when it is lightly or no loaded, its filter caps will keep a high voltage charge for a good long time. I figured a good way to reduce this hazard is to have a bleeder resistor cut in when turning the supply off. I just needed a double pole double throw toggle switch (to replace the single throw single pole I used before). One pole does the powerline, and the other pole will connect the bleeder resistor to the high voltage output when the switch is thrown to "power off". I used a power resistor of about 2500 ohms 10W as the bleeder. This discharges the caps in about 10 seconds. Yes, the caps are fairly big. 120VAC secondary to a cap, then a choke, and another cap.
Having the bleeder not connected while power is on cuts current waste, until I need it when I turn it off.
-------------------- transformer primary
powerline---o o o nc
ON OFF switch terminals
nc o o o----resistor------B supply output
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ground nc= no connection
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