Power supply auto cutoff circuit

[Will]

I have a power supply that will charge a couple of capacitors but
needs to be shut off or limited when the proper voltage has been
reached and restart once the capacitor has discharged. The power
supply is capable of providing much more than is needed to charge the
caps. Specifically I am trying to pulse a yag laser using the power
supply is out of an old helium neon laser which is capable of pushing
4-5kv and I need to stop it around 650v. It doesn't have to be
anything fancy or shiny, just reliable.

If anyone can provide any information at all I will be eternally
greatful.....

-Will

 

[D from BC]

I have a power supply that will charge a couple of capacitors but
needs to be shut off or limited when the proper voltage has been
reached and restart once the capacitor has discharged. The power
supply is capable of providing much more than is needed to charge the
caps. Specifically I am trying to pulse a yag laser using the power
supply is out of an old helium neon laser which is capable of pushing
4-5kv and I need to stop it around 650v. It doesn't have to be
anything fancy or shiny, just reliable.

If anyone can provide any information at all I will be eternally
greatful.....

-Will

resistor attenuator + comparator with hysteresis + IGBT
D from BC

 

[ehsjr]

I have a power supply that will charge a couple of capacitors but
needs to be shut off or limited when the proper voltage has been
reached and restart once the capacitor has discharged. The power
supply is capable of providing much more than is needed to charge the
caps. Specifically I am trying to pulse a yag laser using the power
supply is out of an old helium neon laser which is capable of pushing
4-5kv and I need to stop it around 650v. It doesn't have to be
anything fancy or shiny, just reliable.

If anyone can provide any information at all I will be eternally
greatful.....

-Will

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

 

[whit3rd]

I have a power supply that will charge a couple of capacitors but
needs to be shut off or limited
[the power supply] is capable of pushing
4-5kv and I need to stop it around 650v.

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.

 

[legg]

I have a power supply that will charge a couple of capacitors but
needs to be shut off or limited when the proper voltage has been
reached and restart once the capacitor has discharged. The power
supply is capable of providing much more than is needed to charge the
caps. Specifically I am trying to pulse a yag laser using the power
supply is out of an old helium neon laser which is capable of pushing
4-5kv and I need to stop it around 650v. It doesn't have to be
anything fancy or shiny, just reliable.

If anyone can provide any information at all I will be eternally
greatful.....

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