Triggering Stacked IGBTs

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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.