IGBT Modules - Technologies, Driver and Application (Second Edition) - page 69

traced with the same speed and accuracy in the case of regenerative operation, for
example. Furthermore, the term "accuracy" is only relative in all other respects. While
the junction temperature can be determined quite accurately because of the proximity of
the temperature sensor, however, tolerances of up to 10% due to the design of the
system also have to be taken into account. The real advantage of integrated
temperaturemeasurement is the ability to record the temperature quickly because of the
small time constants.
Fig. 1.50
Integrated temperaturemeasurement
Integrated gate resistors R
generally serve to decouple several IGBT chips
connected in parallel within an IGBT module. The datasheets for this type of IGBT
module bring the internal gate resistors connected in parallel together in a single
datasheet parameter. As well as designs that place this resistors on the chip between
the actual gate of the IGBT and the gate contact, there are also variants in which the
"internal" gate resistor is realised by means of separate silicon substrate resistors (if
necessary, in combination with "real" internal gate resistors). The gate resistor is
"internal" in that it is no longer on the chip, but inside the module as a whole. Strictly
speaking, the datasheet values for the internal gate resister also summarise the ohmic
portion of the bonding technology, such as bond wires and track resistances. In relation
to the valueof the actual gate resistor, these portions canusually be ignored.
Additional gate resistors R
are required as stated in the datasheet in series to the
internal gate resistors.
When internal gate resistors are used, there are consequences further down the track
when the application is in use, some of which can be quite significant. These include:
When the topology includes internal gate resistors, measurements of the gate
voltage always involve an error arising from the voltage divider ratio between
the internal and external resistors. It is therefore not possible to measure the
gate voltage "directly" unlessmeasuredat the chip itself.
Because of the internal gate resistors, the effectiveness of the protective
functions that are supposed to suppress undesirable charging of the gate (due
to theMiller capacitanceC
) is diminished.
The datasheet details on the value of the internal gate resistor generally relate
to 25
C. As the temperature increases, which is to be expected in a real-life
1...,59,60,61,62,63,64,65,66,67,68 70,71,72,73,74,75,76,77,78,79,...548
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