Method and circuit for improving the short-circuit stability of a bipolar IGBT

摘要

A circuit for improving the short-circuit stability of an IGBT (12) uses a MOSFET (14) which reduces the voltage fed to the gate electrode of the IGBT during a short-circuit state when switching on, as a result of which the short-circuit current flowing through the IGBT (12) is reduced. A Zener diode (13, 15) is connected between the MOSFET (14) and the gate electrode of the IGBT (12), in order to clamp the voltage of the gate electrode of the IGBT at a predetermined voltage when the MOS transistor is switched on during a short-circuit state. The MOSFET is switched on if the voltage at the collector of the IGBT rises during a short-circuit state. If the fault is of transient type, then the circuit resets the normal gate voltage. The circuit draws only a small current from the gate driver and requires no separate DC voltage source, so that the circuit can be inserted into IGBT modules or used as an interface between the gate driver circuit and the gate electrode. <IMAGE>