Patent ID: 7696650

Claim:
A drive circuit for switching devices, comprising: a first switching device and a second switching device which are connected in series between terminals of a main power supply; a first control power supply taking as reference potential ground potential of said first switching device; a second control power supply taking as reference potential a potential of a connection point of said first and second switching devices; a pulse generator taking as reference potential the ground potential of said first switching device and generating a set pulse signal and a reset pulse signal; and a level shifting device level-shifting the set pulse signal and the reset pulse signal to the reference potential which is the potential of the connection point of said first and second switching devices, and supplying the set pulse signal and the reset pulse signal to a flip-flop circuit and controlling on/off state of said second switching device; wherein said level shifting device comprises: differential amplifier circuits outputting a difference of the set pulse signal and the reset pulse signal, both level shifted to the reference potential which is the potential of the connection point of said first and second switching devices, integrating circuits integrating the outputs of said differential amplifier circuits, and comparator circuits which, when integrated values which are the outputs of said integrating circuits are equal to or exceed a setting value, transmit said signals as regular control signals controlling on/off state to a gate of said second switching device, so that in-phase noise on the set pulse signal and on the reset pulse signal when driving said second switching device is absorbed.