IGBT Modules - Technologies, Driver and Application (Second Edition) - page 214

6 I
6 IGBTDriver
6.1 Introduction
An IGBT gate driver has to perform amultitude of requirements simultaneously. During
the IGBT turn-on the gate capacitance is charged and upon reaching the IGBT
threshold voltage, also the reverse transfer capacitance (Miller capacitance). To turn off
the IGBT, the input capacitance has to be discharged and, once the threshold voltage is
reached, also the reverse transfer capacitance. Further, the IGBT driver may take over
protection functions, which protects the IGBT from destruction. These include IGBT
short circuit and overvoltage protection. Also, a driver can influence the dynamic
behaviour of the IGBT and the freewheeling diode. In addition, potential separation of
the input circuit (low-voltage side) and the output circuit (high-voltage side) has to be
ensured. The low-voltage side is the interface to the control electronics. The high-
voltage side is connected to the IGBTs. The separation is necessary, because the
emitter potential of the upper IGBTs is switched between the DC+ and DC- potential of
theDC-bus, as can be seen i
Fig. 6.1
Example of the use of IGBT gate drivers with optocouplers in an inverter
system (each IGBTdriver has its own power supply)
In the simplest case, it may be sufficient to separate only the upper IGBTs of a half-
bridge from the bottom IGBTs. This is generally possible if the microcontroller is also
referenced to the DC- potential. A subsequent separation of the interconnection to the
user interface is advised or required, depending on the application. In high power
applications, potential separation takes place at every IGBT, each with its own power
supply as shown i
The complexity for the power supply can be simplified for those switches, which have
their emitter onDC- potential, as shown in
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