Abstract: A magnetic part having a first iron core wound with a winding constituting a transformer and an inductance component of a parallel coil and a second iron core wound with an inductance component of a series coil, in which a ratio of the dimensions of the first iron core and the second iron core are in accordance with their respective winding densities.

Abstract: A drive circuit for a current sense IGBT having, in addition to a fault discrimination operational circuit for detecting an overcurrent of the current sense IGBT, a capacitor operatively connected in parallel to the gate-emitter of the current sense IGBT, and a transistor for discharging the capacitor via a resistor. In case of short-circuit fault, an overcurrent is detected by the fault discrimination operational circuit, and the transistor is turned on via the operational circuit. The gate voltage of the IGBT is gradually declined to turn off the IGBT. This enables the IGBT to be protected from a transitional overvoltage across the collector and emitter of the IGBT.

Abstract: A drive circuit for a voltage driven type semiconductor device having a serial circuit of a resistor and a Zener diode. One terminal of the serial circuit is connected to an output terminal (collector) of the semiconductor device. An overcurrent flowing in the semiconductor device is detected based on a current flowing through the serial circuit and the presence or absence of a drive signal fed to the drive circuit from an external control circuit. The detection level of the overcurrent can be adjusted by the voltage of the Zener diode, and the quick detection becomes possible. This arrangement makes it possible to detect an overcurrent in the semiconductor device, and hence to detect a shortcircuit in a circuit connected to that device in a minimal time required, thereby reducing the energy consumed in the semiconductor device during the short circuit.

Abstract: In a common drive output circuit for driving dissimilar switching semiconductor devices having different drive input characteristics by turning on and off dc power supplies to apply a voltage between the drive input terminals of either one of the switching semiconductor devices through two transistors connected in a Darlington pair, the collector circuit of one of the two transistors which is not at the output stage has a diode inserted in series which has such a polarity as to permit passage of the collector current.