Reverse voltage across IGBT

[Ignoramus12123]

Let's say that due to whatever, there is momentary reverse voltage
across the IGBT. Just what levels are actually harmful? My IGBT is of
the 1,200 V rated variety. I am not sure how reverse voltage can
damage an IGBT.

i

 

[Winfield Hill]

Ignoramus12123 wrote...

Let's say that due to whatever, there is momentary reverse voltage
across the IGBT. Just what levels are actually harmful? My IGBT is
of the 1,200 V rated variety. I am not sure how reverse voltage can
damage an IGBT.

Did you lose another one?

 

[Tim Williams]

Well, you can get IGBT's with internal body diodes. That's what I got...

I don't remember if the IGBT structure behaves like a MOSFET or a BJT
overall. A MOSFET has an intrinsic body diode (since the substrate is tied
to source), although it isn't necessarily rated for duty. An IGBT is often
mentioned as a MOSFET + BJT "Darlington", in which case the big part would
act like a BJT, no?

On a related subject, what happens when you reverse-bias a generic power
transistor, 2SC2625 for example? (800V 10A, I think, NPN power transistor
used in computers the world around for a good decade or so.) Obviously the
C-B junction gets forward-biased, which will tend to pull the base down as
well. But then, current starts diffusing through from the emitter, no? How
much current would this withstand, would it be comparable to Ice(max)?

Tim

 

[Ignoramus12123]

Ignoramus12123 wrote...

Did you lose another one?

Not yet... But I do not want to.

i

 

[Fritz Schlunder]

Let's say that due to whatever, there is momentary reverse voltage
across the IGBT. Just what levels are actually harmful? My IGBT is of
the 1,200 V rated variety. I am not sure how reverse voltage can
damage an IGBT.

You'll have to consult your IGBT's datasheet, but... Typically with the
gate at zero volts, reverse collector emitter breakdown will occur nearish
20 volts for common IGBT devices.

Some IGBTs have a reverse avalanche energy specification. Apparently
avalanche rated devices can successfully survive reverse avalanche events
provided certain requirements are met (such as maximum avalanche energy is
not exceeded). This particular feature doesn't seem to be too well
characterized, as far as I can tell.

This document:

http://www.irf.com/technical-info/appnotes/an-983.pdf

Mentions the effect a couple of times briefly in sections 8.2 and 8.4.