RE: Triggering Stacked IGBTs

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Leigh Copp" <Leigh.Copp@xxxxxxxxxxx>

Steve,

Fiber optically triggered, and galvanically isolated (I.E. seperate, 
isolated gate drive power supplies for each device) are the tools of 
choice in MV/HV applications.

It is very diffcult to match the propagation delay of multiple pulse 
transformers.

An interesting variation on this however is to use a current pulse to 
drive multiple -current- transformers, used as pulse transfomers. 
This way the entire series stack sees the the same thing on the 
primary at the same time.

Leigh

        -----Original Message-----
        From: Tesla list [mailto:tesla@xxxxxxxxxx]
        Sent: Sat 17/02/2007 12:39 AM
        To: tesla@xxxxxxxxxx
        Cc:
        Subject: Triggering Stacked IGBTs



        Original poster: "S&JY" <youngs@xxxxxxxxx>


        I am looking for ideas on practical and not overly expensive ways to
        trigger a stack of IGBTs.  For example 10 1,200 volt IGBTs in series
        to take the place of a spark gap.

        The SISG (SIDACs) scheme is good, but I want more control.  I would
        like to be able to externally vary pulse rep rate, pulse width and
        the DC voltage to the stack independently.  I suppose I am after a
        poor-man's variant of a klystron modulator such as used in particle
        accelerators.

        One method is to use fiber optic coupling to photo detectors
        controlling each IGBT.  I have read these are susceptible to
        electrical noise.  Other methods use pulse transformers, e.g.
        modulated several mHz inputs and rectify the outputs to control the
        gate.  Or use pairs of pulse transformers to trigger a flip flop on
        and off to control the IGBT gate.  Of course, whatever scheme is used
        must trigger all the gates simultaneously.  And the trigger circuits
        on the IGBT side must derive their power from the main DC power to
        the IGBT stack (to avoid the need for isolated power supplies).

        Can some of you steer me to a source of ideas?  Better yet, can any
        of you report your practical experience triggering series 
connected IGBTs?

        Thanks,

        --Steve Y.