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Thread: Power Supplies

  1. #1
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    Default Power Supplies

    I'm looking at converting my positive output HV supply (capacitor charging) to a negative output supply. These capacitors discharge through flash lamps that require the anode side of the lamps to be positive relative to the cathode side of the lamps. If the anodes are connected to ground (through the HV switch) and the cathodes become the HV (-) supply, am I cool? The trigger circuit will have to be inverted as well, but that's a simple rewiring. Am I missing something?

  2. #2
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    No thoughts on this?

  3. #3
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    can you draw a schematic?

  4. #4
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    Actually...I don't want to. I'm not being stubborn, I just think it would take me a long time to sketch something in Paint and post it. Ultimately, I suppose I could, but it is the concept that I am most curious about. In general, flash lamp charging circuits are drawn and built to drive these lamps with a positive anode voltage relative to ground. I am happily cranking out kW into these lamps with this arrangement. I want to replace my big, bulky (and inefficient) linear power supply with a pulsed, constant current switching supply, but the output in this case is negative relative ground.

    Maybe I am being naive, but I would think that as long as the anode side of the lamp remains electron deficient relative to the cathode, there would be no problem. The cathode would then no longer be common with ground and the anode would become common to ground. Is this weird or not?

  5. #5
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    The concept seems sound. The lamp won't know the difference. My concerns would be the input of the trigger circuit is isolated from the HV circuit. And what ever device is triggering the lamp is now on the correct side of the lamp.

    Mixedgas has more experience on these things. Hopefully he chimes in.

  6. #6
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    The trigger is a capacitively coupled plate(reflector), (+)50kV through the xenon, grounding through the cathode to the capacitor bank @ around +/- zero volts (now) and grounding to the new (-)4 to (-)6kV cathode, yet to be.

    Steve?

  7. #7
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    Pulse is done with a trigger coil?
    How many volts does the tube operate at? If its like 400-600 or I guess less than maybe 2kv you could upgrade/add something like an IGBT + simmer ignition

  8. #8
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    Each of the four tubes has a hold off up to approximately 2200V and then would spontaneously and unpredictably discharge. When triggered, all four of these tubes will conduct a precisely timed pulse (jitter at < 1 usec) from the main capacitors that can be as little as 800 V. The common,adjustable, over voltage spark gap that is in line with the cathode side of the tubes allows the operating range of 800V to 2200V to be elevated to as high as I want it, up to the maximum energy capacity of the lamps. The trigger is an adjustable, 50-60kV, 8J, 4usec pulse from a coil that is conducted to the aluminum housing that supports the chamber reflectors. The original trigger wires absorbed some pump light and were removed. The chamber is 9cm in diameter and 30 cm long. Main pulse energies are up to 4,000J, 30usec long and 20kA.

  9. #9
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    pics? unless this is somewhere cameras are not allowed

    reflector electrically floating? air or watercooled? one end of the trigger coil secondary goes to the reflector, where does the other go?
    the lamp anode has to stay positive if its designed as such since the electrodes would be different, ie one pointy the other round or something like that and/or different compositions (tungsten with something radioactive added)

  10. #10
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    Take a look at these:
    http://www.photonlexicon.com/forums/...3636-New-Laser

    This was a couple of months ago and the trigger wires are gone, but the reflector is very much as it is shown here. The reflector is floating and air cooled (for this reason). The ground of the trigger is now directly connected to the zero volt, cathode ground and would then be connected to the zero volt anode "ground". The main pulse would still be positive on the anode end of the lamps relative to the cathode.

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