Power supply auto cutoff circuit

resistor attenuator + comparator with hysteresis + IGBT D from BC

Murphy says your shut-off circuit will fail and you'll blow your laser/other components all to hell. Better would be to design the supply to ~650 maximum.

Ed

Easiest might be an optoisolator with a neon lamp (turns on at about 100V) with the output used to turn off a solid state relay (SSR). Power the laser supply through the SSR, of course. To drop the extra 500V, some combination of neon lamps, zener diodes, transzorb breakdown devices would be my choice. And a series resistor, just to keep the neon lamp from turning TOO hard on.

Modify the voltage regulation loop to produce 650V. This will involve increasing o the shunting element in the voltage divider of the feedback network.

You seem to be satisfied with the current regulation loop (ie the charging current) - however you should ensure that constant operation at this current level is acceptibly within the unit's specifications.

This assumes that the supply has sufficiently secure housekeeping capability at this very different low voltage operating condition.

You may have to add output bleeders to provide a minimum load at the new regulation point.

RL