IGBT Modules - Technologies, Driver and Application (Second Edition) - page 254

6 I
behaviour with R
(though not asmuch as the turn-on process). In Trench-FS IGBTs,
on the other hand, this influence is virtually non-existent as long as R
does not
extend to extremely high values. This can be observed, for example, using the switching
losses as a function of the gate resistor
and in the measurement of
Fig. 6.39
Measurements of the switching delay in turning on and off a Trench-FS IGBT
as a function of thegate resistor
If very high gate resistor values are used in proportion to the nominal gate resistor
value, a Trench-FS IGBT can be driven into desaturation during turn-off. This leads to a
softer rise in the collector-emitter voltage, on the other hand, to a faster drop of the
collector current. The latter will result in a greater voltage overshoot at turn-off, given the
same stray inductance of the commutation circuit. In extreme cases, the collector
current may decaywithout tail current, which can lead to strong oscillations in addition.
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