Fuji Electric Co., Ltd.

Masafumi Tabata

Seiki Igarashi

A current detector includes a chopper circuit composed of a switching circuit, i.e. an inverse-parallel circuit composed of an insulated gate bipolar transistor IGBT and a diode, and a switching circuit, i.e. an inverse-parallel circuit composed of an IGBT and a diode, which are connected in series. When the diode on the opposite arm is turned on, a reverse recovery current is detected and its output is directed to a gate drive circuit via an insulating circuit. A switch in the gate drive circuit is opened to increase resistance, in order to reduce the speed at which the gate of the switching device is charged. Thus, the surge voltage and its increase ratio are reduced without reducing a switching speed or requiring a snubber circuit.

Gate drive circuit for power converters that reduces surge voltages

A balancing circuit balances the steady-state currents of the switching devices in an electric power converter, which facilitates reducing the size of the power converter and precisely balancing the steady-state currents. The balancing circuit holds transient sensing voltages at the time of turning-on of the switching devices, and detects the unbalance between the currents of the switching devices based on the distribution or unbalance of the sensing voltages by comparing the steady-state sensing voltages or the values corresponding to the steady-state sensing voltages with the stored transient sensing voltages. The steady-state currents of the switching devices are balanced by regulating the drive voltages of the switching devices based on the detected distribution of the steady-state currents.

Growing community of inventors

Tokyo, Japan

Masafumi Tabata