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Power supply auto cutoff circuit

Discussion in 'Electronic Design' started by Will, Jun 16, 2007.

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  1. Will

    Will Guest

    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

  2. D from BC

    D from BC Guest

    resistor attenuator + comparator with hysteresis + IGBT
    D from BC
  3. ehsjr

    ehsjr Guest

    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.

  4. whit3rd

    whit3rd Guest

    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
  5. legg

    legg Guest

    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.

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