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short circuit protection of IGBT?
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coppercone2:

"thermal runaway after successful turned off"

will this be prevented if you use a ridiculous non cost effective device to block the current flow rather then messing with the gate if it was about to happen?

say its connected to the IGBT right up against it with the least amount of inductance possible.
coppercone2:

--- Quote from: David Hess on December 28, 2018, 07:39:49 pm ---I do not remember where now but I saw IGBT short circuit protection implemented using a low voltage high current power MOSFET in series with the emitter of the IGBT.  Under normal conditions, the IGBT gate controlled switching but under fault conditions, the gate of the power MOSFET was clamped low very quickly disconnecting the emitter of the IGBT and driving the gate voltage of the IGBT negative.

--- End quote ---

based on your understanding does this like specifically target one of the failure modes described by the picture?
coppercone2:

--- Quote from: blueskull on December 28, 2018, 08:50:25 pm ---
--- Quote from: coppercone2 on December 28, 2018, 08:21:48 pm ---Which one of these does the "energy shock" described by the paper I linked fit into?

--- End quote ---

Energy pulse breakdown can show itself as filamentation breakdown, or FBSOA secondary breakdown, depending on when the energy pulse is received.
If the energy pulse is received before device turns off, i.e. a gross overload, then filamentation is more likely to happen.
If the energy pulse is received after device turning off, i.e. an inductive kickback, then a secondary breakdown is more likely to happen.

--- End quote ---

so energy pulse is completely synonymous with the definition of energy shock used in the paper if I wanted to do further research?

the paper does not seem to put energy shock into the same category as over voltage.
coppercone2:
so it kinda sounds like, if this FBSOA breakdown is going to happen, it means the gate is no longer in true control of the current going through the circuit, and some kind of external device is required to block the current.

How does the 1uS time constant work described in the paper as the time after device turn off and device breaking work in terms of FBSOA?

so if t=0 at turnoff, and you literary teleport the device out of the circuit, does it still break or are they saying its not really turned off just the gate is 0V and it still draws current? its not like internally stored energy in the silicon that goes and focuses in the wrong places or something like that right, it shows a impedance if you had a meter on it proportional to how much energy it would need to consume in 1uS to break itself? or if you had a ammeter on the power rail it would still draw current despite its definition of being turned off?

am i being confused by latch up?
max_torque:
An important question is really "what actually am i trying to protect against"??

Most high power switching systems are optimised to run under a defined condition, and generally, they accept (for non life critical applications) that some failure modes do exist that could result in mortality of the switching element. The question then becomes "What is the probability of those failure modes occuring" and "what happens if the switching element does fail".

This is why, you never really see any separate switching element used to "protect" the primary switch itself....

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