RE: Series connection of Mosfets/IGBTs

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Mccauley, Daniel H" <daniel.h.mccauley-at-lmco-dot-com> 


Yes Greg, but those HV IGBT's are basically just a series connection of
single FETs anyways.
Also, they (particularly the HV IGBTs) are still relatively low PRF type
devices.  I don't believe
you could get 300kHz operation out of them.

Also, at the current price tag, they are well above the price range for
most amateurs and there is slim
chance they'll start showing up on EBAY anytime soon.


Dan



 >Dear forum members,
 >
 >I have seen parallel connection of MOSFETs to increase the load current

 >capability. Anybody in this forum tried series connection of
 >MOSFETs/IGBTs and increase the supply voltage to greater than 2KV ?


It's possible, but requires a *considerable* deal of care to equalize
the
stack voltages during both slow and fast fault conditions.  It's far
easier
and more reliable to just use the higher voltage silicon.  The
Mitsubishi
4.5kV silicon is fine for up to 3kV working voltage, and the Infineon
6.5kV
silicon works reliably up to 4kV+.  Mitsubishi has also just announced a

6.5kV process, with beta samples now on the street.  At work last week
we
received a 6.5kV, 24-die package for evaluation, that should be suitable

for 6kA pulsed service.
When higher output voltages are needed, historically the preferred
method
is to use pulse xfmrs or fractional-turn xfmrs to combine multiple IGBT
drive circuits in series.