Re: Long Pulse IGBT GDT design

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Original poster: "B2" <bensonbd-at-boo-dot-net> 

e-mail-19263

Hi Dave,
     I used a Radio Shack 120V to 12V transformer for the same purpose 
(choice arrived at by trial and error).  I tried a few toroids.  They were 
all too fast and the L/R was too short for my need.  A floating pulse 
stretcher circuit was considered, but the design time was not 
available.  In the end, I decided on a long L/R with a clipper.   I had to 
build a simulator that duplicated a bomb droping off a jet and being armed 
while it was simultaneously being struck with lightning (fun test).  I 
needed to simulate a 0.1 second pulse using power mosfets (IRF450).  The 
gate (series) resistor was around 100 Ohms (adjust for your L/R).  A 15 
Volt zener diode and 50 ohm resistor in parallel with the gate clipped the 
extra voltage. That is all that I can remember, as I do not have access to 
the circuit. Hope that is helpful.

Barry

>Need some design guidance for a GDT for an IGBT power switch.  Need to turn
>on for ~300usecs, off time of 1.5millisecs (PRF = 400Hz).  If drive 
>voltage is 30Vpk to pk, results in a V*t product of 9000V-usecs (typical 
>GDT product is in
>200-500V-usecs).
>
>Transformer may saturate, but will DC restore during off time so not 
>particularly
>a big deal.  Any design guidance out there for DC restoration using 
>standard toroids for long pulse IGBT gate drive?
>
>Thanks!
>
>Best Regards
>Dave Sharpe, TCBOR/HEAS
>Chesterfield, VA. USA