Patent ID: 8610485

Claim:
A gate drive circuit, comprising: a turn-on circuit having an upper limiter for receiving a gate drive signal, the upper limiter having an output terminal; a transistor having a base connected to the output terminal of the upper limiter, and a terminal connected to a gate of a power switching device, wherein the upper limiter limits a voltage input to the base of the transistor to not exceed a first predetermined value; and a first predetermined value varying circuit configured to vary the first predetermined value, wherein the first predetermined value varying circuit comprises: a plurality of zener diodes all connected in a series circuit to the base of the transistor; and a plurality of terminal pairs, each one of the terminal pairs being connected to a respective end of a respective one of the zener diodes, with the plurality of terminal pairs being configured to permit a predetermined constant current to flow through a respective zener diode so that the anode and cathode of the respective zener diode is substantially electrically shorted together to vary the first predetermined value in accordance with a number of respective series connected zener diodes having the anode and cathode thereof substantially electrically shorted together.