n-channel push-pull driver stagewithBJTandMOSFET
If an IGBT is switched on conventionally the charge current is based on the gate
resistance and the driving gate voltage. Initially, in the turn-on phase, the voltage across
the IGBT gate-emitter is 0V or negative (depending on the applied turn-off gate voltage)
and the peak charge current is limited only by the gate resistor and the gate inductance.
The input and reverse transfer capacitances of the IGBT are charged until themaximum
voltage (typically 15V) appears at the gate.
IGBTgateboostingwith auxiliary boost voltage
Oneway to reach the level of the threshold voltageU
of the IGBT faster is to boost
the gate. By enforcing a higher gate current the IGBT can be switched on faster. To
ensure a soft commutation of the diode, the charging process will be slowed down once
the threshold voltage is reached. With this method it is possible to reduce the turn-on
losses of the IGBT by a double-digit figure without damaging the diode. In practice, a