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How rugged is an IGBT internal diode.

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cupoftea

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hI,
We all know how IGBTs can break short circuit currents and survive, unlike MOSFETs........but how rugged is the diode that gets put with them...?
For example, if there is severe reverse recovery current flow in that diode, then i would wager that its just as likely to fail as a MOSFET?...would you agree?

IXER35N120 IGBT
 

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IGBT diodes are designed to handle turn off better than most diodes - this is because IGBT's can in fact turn on very fast if you drive the gate, so the diode in the other device has to recover under arduous conditions - so they have a softer recovery characteristic - this adds of the cost of a good IGBT - and raises the heat in the diode - but they happily survive with good heatsinking ...

mosfets are rarely subject to the same stresses ( as they just go bang ) due to inferior internal didoes for > 200V parts ...
 
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In contrast to vertical MOSFET, IGBT have no built-in substrate diode. IGBT with integrated diode are two chip combos. IGBT bridges have no problem with hard commutation at rated current, diode turn-off losses are fully specified.

High voltage MOSFET have a specific problem with hard commutation out of diode conduction due to a parasitic thyristor structure. It's reflected in a maxium reverse recovery dV/dt spec.
 
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High voltage MOSFET have a specific problem with hard commutation out of diode conduction due to a parasitic thyristor structure. It's reflected in a maxium reverse recovery dV/dt spec.
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Thanks, i think this is one of the big potential problems wth PSFB's and other bridge converters which have high leakage inductance and highish magnetising current
 

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You can take simpler examples like regular synchronous buck converter. Your options:
- set the dead time to a minimal but still safe value so that only part of the load current is transferred to the diode
- reduce turn-on gate current to reduce dV/dt
--- Updated ---

- use soft switching topologies, e.g. with auxiliary switches (ARCP, pre-switch)
 
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