Re: Long Pulse IGBT GDT design

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

Original poster: "Jan Wagner" <jwagner-at-cc.hut.fi> 


On Sun, 10 Oct 2004, Tesla list wrote:
>Original poster: sparktron01-at-comcast-dot-net Hi Jan
>
>Yes, I downloaded that AN today; will try to "throw together" Figure 5 
>with IGBT's and IEEE dynamic voltage equilization circuit, and see what 
>happens (like "run for cover!!!
>
>   ;^))))

If you use a resistor accross IGBT gate and emitter, watch out it's not too 
small resistance, otherwise you might really have to run for cover! :)
Same situation if there are to be expected some heavy voltage transients 
that might couple back to the gate signal... ;)

>Speed looks right (~100nS turn on and off), FET is rated to nearly 20A 
>pulse.  Might even be able to use a Radio Shack type IRF510 / IRF511 
>variant for driving to keep
>cost down.

Btw there's also a slighlty simpler circuit at
   http://dsms.ajusd-dot-org/~fritz/AN1.pdf
that runs very nicely, but has some "startup" time, and you can't change to 
duty cycle too fast either. Other circuits like Dan's ultrafast gatedrive 
are at the end of:
   http://www.hut.fi/~jwagner/tesla/SSTC/general-sstc-notes-gatedrv.htm

But if you need a really rigid drive that can also handle arbitary duty 
cycles, then the only way is to set up auxiliary floating supplies for each 
IGBT. E.g., 1MHz 50% duty oscillator and some small ferrite cored 1:1:1:... 
xfmr (with good RF/HV insolation...) to generate the supplies, some minor 
voltage regulation, and a standard gate drive chip for each IGBT, plus fast 
optos (cheap HCPL-3020's?) to steer these.

At higher cost you could use dedicated opto/driver combo chips that have 
all sorts of extra features, like fault and igbt saturation detection, and 
whatnot. For example chips from Agilent:
  http://www.agilent.co.jp/spg/products/pdf/optocoupler/HCPL316J.PDF

cheers,
  - Jan

-- 
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  Helsinki University of Technology
  Dept. of Electrical and Communications Engineering
  http://www.hut.fi/~jwagner/ - jwagner-at-cc.hut.fi