IGBT with positive source

Discussion in 'The Projects Forum' started by Mira7, Jun 26, 2013.

  1. Mira7

    Thread Starter New Member

    Jun 26, 2013
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    I have successfully used the Agilent HCPL-3180 optocoupler to drive an HGTD3N60A4 IGBT with grounded source. How would one drive the IGBT when the source is positive (15V or more "vref" provided by some energy source)?
     
  2. crutschow

    Expert

    Mar 14, 2008
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    3,241
    Connect the opto coupler between the IGBT gate and the IGBT source.
     
  3. Mira7

    Thread Starter New Member

    Jun 26, 2013
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    Thank you, crutschow.

    This presents the problem of powering the IGBT driver ICs. I need IGBTs at three different energy levels (0V, low two-digit volts, and three-digit volts). One could use several 15V batteries, however I would like a solution based on a single energy source that does not short the IGBTs at different energy levels. How can this be achieved?

     
  4. aws505

    Member

    Mar 11, 2013
    59
    7
    The only way I've seen it done is with multiple batteries. You may be able to do it with some clever inductive charging, though. We actually charge our IGBT driver batteries back up with an inverter through an inductive charging system. Maybe you could, instead, just charge a (large) cap via inductive charging to power your circuit?
     
  5. wayneh

    Expert

    Sep 9, 2010
    12,148
    3,058
    For an AC source, you can use a bootstrap arrangement where a capacitor is charged through a diode on the low part of the cycle, and then rises up on top of the high side of the cycle. The capacitor has to be large enough to power the driver and the IGBT through the cycle. Hard to say without knowing anything about the rest of the circuit.
     
  6. Mira7

    Thread Starter New Member

    Jun 26, 2013
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    I noticed that there exist isolating unregulated DC/DC converters with 15V or +-15V output. I am thinking this is similar to the battery solution except I can use a single 5V or 15V supply. I am not sure if each isolated output needs to be regulated, say with an LM7815, though.
     
  7. aws505

    Member

    Mar 11, 2013
    59
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    Hmm... I suppose that's a good point. If you put your power through an isolated DC/DC supply, you should be able to have each supply, essentially, floating. Just make sure that your isolated DC/DC supply is rated for the voltage you're expecting on the IGBTs and, of course, give yourself some overhead. If you're expecting 500V on the IGBT, I'd recommend that your supplies be rated for at least 750V isolation -- 1kV would be better.

    As for regulating, you can probably get away without regulation, but it probably wouldn't hurt. If you choose to go unregulated, then some sacrificial diodes may be a nice easy way to protect your electronics.
     
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