Re: Large IGBT need help

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

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


On Wed, 14 Apr 2004, Tesla list wrote:
 > Original poster: Fucian-at-aol-dot-com
 > In a message dated 4/13/2004 8:20:30 PM Eastern Standard Time,
 > tesla-at-pupman-dot-com writes:
 > The gate charge varies with voltage.  Go look at the datasheet and calculate
 > the gate capacitance.
 > Use the equation C = Q/V where C = capacitance [farads]
 >                       Q = charge [coulombs]
 >                       V = potential [volts]
 >
 > Regards - Jim Mitchell
 >
 > haha, who really goes by coulombs except for physicists...???

Well, electronics engineers, for one. ;)

 > I will take another look at the sheet...I think that 30volts was the max on
 > the gates, so i will try to go with that...
 >
 > I iwll need to use discreets since the driver chips cant go over like
 > 15volts...

30V isn't necessary, unless you try pushing a few kA peak through the
IGBT. And don't forget that if you raise the gate drive voltage, also the
peak gate charging current rises. Not a problem if you use discretes, but
with chips you could exceed the peak current output rating and get much
slower switching than you'd expect. Just some things to remember.

good luck!

cheers,
  - Jan

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  Helsinki University of Technology
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