Abstract: A gate drive circuit according to an embodiment includes: a voltage detector that detects a voltage between a first terminal and a second terminal of a switching device; a delay circuit that outputs, with a delay for a predetermined time, a detected value of the voltage obtained from the voltage detector; and a first off-mode drive circuit and a second off-mode drive circuit that apply a control signal to a control terminal of the switching device for turning off the switching device, wherein the first off-mode drive circuit turns off the switching device faster than the second off-mode drive circuit, and stops its operation to turns off the switching device when the delayed voltage value output from the delay circuit exceeds a predetermined threshold value.

Abstract: A power conversion device includes: a first power conversion circuit that converts power inputted from outside and outputs the converted power to a second power conversion circuit connected to the first power conversion circuit via a DC link, which outputs the converted power to a load; smoothing capacitors provided in an output part of the first power conversion circuit and an input part of the second power conversion circuit; a first and second common mode current extraction circuits provided in an input part of the first power conversion and second power conversion circuits; and a virtual neutral potential line that connects the first and second common mode current extraction circuits; a DC link filter circuit that includes a Y-shaped capacitor connected between the DC link part and the virtual neutral potential line.

Abstract: A power conversion device includes: a first power conversion circuit that converts power inputted from outside and outputs the converted power to a second power conversion circuit connected to the first power conversion circuit via a DC link, which outputs the converted power to a load; smoothing capacitors provided in an output part of the first power conversion circuit and an input part of the second power conversion circuit; a first and second common mode current extraction circuits provided in an input part of the first power conversion and second power conversion circuits; and a virtual neutral potential line that connects the first and second common mode current extraction circuits; a DC link filter circuit that includes a Y-shaped capacitor connected between the DC link part and the virtual neutral potential line.

Abstract: A semiconductor device according to one embodiment includes a first normally-off type transistor including a first source, a first drain, a first gate, and a first body diode, a second normally-off type transistor including a second source connected to the first source, a second drain, a second gate connected to the first gate, and a second body diode, a normally-on type transistor including a third source connected to the first drain, a third drain, and a third gate connected to the second drain, and a diode including an anode connected to the second drain and a cathode connected to the third drain.

Abstract: According to one embodiment, a switch includes a first element with a first withstand voltage, a second element whose withstand voltage is lower than the first withstand voltage, a diode which is connected between a positive electrode of the first element and a positive electrode of the second element in such a manner that a direction from the positive electrode of the second element toward the positive electrode of the first element is a forward direction and whose withstand voltage is equal to the first withstand voltage, a negative electrode of the first element and a negative electrode of the second element being connected, and a circuit configured to apply a positive voltage to the positive terminal output a pulse lower than the first withstand voltage when the first element goes off.

Abstract: A semiconductor device according to one embodiment includes a first normally-off type transistor including a first source, a first drain, a first gate, and a first body diode, a second normally-off type transistor including a second source connected to the first source, a second drain, a second gate connected to the first gate, and a second body diode, a normally-on type transistor including a third source connected to the first drain, a third drain, and a third gate connected to the second drain, and a diode including an anode connected to the second drain and a cathode connected to the third drain.

Abstract: A reactive power compensator according to an embodiment comprises: multilevel inverter circuits respectively constituting each of the three phases; a filter circuit for reducing harmonics connected between the output terminals of each of the multilevel inverter circuits and a power system interconnection terminal; and a control section for causing prescribed three-phase AC voltage to be output by controlling each of said multilevel inverter circuits. Each of the multilevel inverter circuits is constituted by connecting in series one or more single-phase full-bridge single-pulse inverters and is arranged to convert DC voltage to respective positive and negative single-pulse voltages once per cycle of the fundamental wave of the voltage instruction value.

Abstract: According to one embodiment, a switch includes a first element with a first withstand voltage, a second element whose withstand voltage is lower than the first withstand voltage, a diode which is connected between a positive electrode of the first element and a positive electrode of the second element in such a manner that a direction from the positive electrode of the second element toward the positive electrode of the first element is a forward direction and whose withstand voltage is equal to the first withstand voltage, a negative electrode of the first element and a negative electrode of the second element being connected, and a circuit configured to apply a positive voltage to the positive terminal output a pulse lower than the first withstand voltage when the first element goes off.

Abstract: According to one embodiment, a switch includes a first element with a first withstand voltage, a second element whose withstand voltage is lower than the first withstand voltage, a diode which is connected between a positive electrode of the first element and a positive electrode of the second element in such a manner that a direction from the positive electrode of the second element toward the positive electrode of the first element is a forward direction and whose withstand voltage is equal to the first withstand voltage, a negative electrode of the first element and a negative electrode of the second element being connected, and a circuit configured to apply a positive voltage to the positive terminal output a pulse lower than the first withstand voltage when the first element goes off.

Abstract: A semiconductor device according to the embodiments includes: a first normally-off transistor including a first source terminal, a first drain terminal, and a first gate terminal; a normally-on transistor including a second source terminal connected to the first drain terminal, a second drain terminal, and a second gate terminal connected to the first source terminal; a protection element provided between the first gate terminal and the second drain terminal, and having breakdown voltage lower than breakdown voltage of the normally-on transistor; and a first diode including a first anode connected to the second drain terminal and a first cathode connected to the protection element.

Abstract: A semiconductor device according to the embodiments includes: a first normally-off transistor including a first source terminal, a first drain terminal, and a first gate terminal; a normally-on transistor including a second source terminal connected to the first drain terminal, a second drain terminal, and a second gate terminal connected to the first source terminal; a protection element provided between the first gate terminal and the second drain terminal, and having breakdown voltage lower than breakdown voltage of the normally-on transistor; and a first diode including a first anode connected to the second drain terminal and a first cathode connected to the protection element.

Abstract: According to one embodiment, a semiconductor switch includes a main element including a switching element and an antiparallel diode, and a reverse voltage application circuit. The reverse voltage application circuit includes an auxiliary electric-power supply, a high-speed free wheeling diode, an auxiliary element, and a capacitor. The high-speed free wheeling diode comprises a plurality of diodes connected in series.

Abstract: A reactive power compensator according to an embodiment comprises: multilevel inverter circuits respectively constituting each of the three phases; a filter circuit for reducing harmonics connected between the output terminals of each of the multilevel inverter circuits and a power system interconnection terminal; and a control section for causing prescribed three-phase AC voltage to be output by controlling each of said multilevel inverter circuits. Each of the multilevel inverter circuits is constituted by connecting in series one or more single-phase full-bridge single-pulse inverters and is arranged to convert DC voltage to respective positive and negative single-pulse voltages once per cycle of the fundamental wave of the voltage instruction value.

Abstract: Disclosed is a power conversion device which achieves reductions in switching loss due to a reverse recovery current and heat generation loss. Specifically disclosed is a power conversion device provided with a cascode element configured by electrically connecting a normally-on switching element and a normally-off switching element in series and connecting a gate terminal of the normally-on switching element and a source terminal of the normally-off switching element via a cascode connection diode, and a high-speed diode electrically connected in parallel with the cascode element and having a cathode region connected to a positive electrode terminal and an anode region connected to a negative electrode terminal.

Abstract: According to one embodiment, a switch includes a first element with a first withstand voltage, a second element whose withstand voltage is lower than the first withstand voltage, a diode which is connected between a positive electrode of the first element and a positive electrode of the second element in such a manner that a direction from the positive electrode of the second element toward the positive electrode of the first element is a forward direction and whose withstand voltage is equal to the first withstand voltage, a negative electrode of the first element and a negative electrode of the second element being connected, and a circuit configured to apply a positive voltage to the positive terminal output a pulse lower than the first withstand voltage when the first element goes off.

Abstract: According to one embodiment, a semiconductor device includes a semiconductor circuit and an electric-power supply. The semiconductor circuit includes a main element including a switching element and an antiparallel diode, a reverse voltage application circuit including a high-speed free wheeling diode, a capacitor and an auxiliary element, a main element drive circuit, and an auxiliary element drive circuit. The electric-power supply is configured to supply electric-power to the capacitor, the main element drive circuit and the auxiliary element drive circuit, and has a voltage lower than the withstand voltage of the main element.

Abstract: According to one embodiment, a semiconductor switch includes a main element including a switching element and an antiparallel diode, and a reverse voltage application circuit. The reverse voltage application circuit includes an auxiliary electric-power supply, a high-speed free wheeling diode, an auxiliary element, and a capacitor. The high-speed free wheeling diode comprises a plurality of diodes connected in series.

Abstract: Disclosed is a power conversion device which achieves reductions in switching loss due to a reverse recovery current and heat generation loss. Specifically disclosed is a power conversion device provided with a cascode element configured by electrically connecting a normally-on switching element and a normally-off switching element in series and connecting a gate terminal of the normally-on switching element and a source terminal of the normally-off switching element via a cascode connection diode, and a high-speed diode electrically connected in parallel with the cascode element and having a cathode region connected to a positive electrode terminal and an anode region connected to a negative electrode terminal.

Abstract: A semiconductor switch is provided with a main element having reverse conductivity and serving as a voltage-driven switching element having a high withstand voltage, an auxiliary element serving as a voltage-driven switching element having a withstand voltage lower than that of the main element, and a high-speed freewheel diode having a withstand voltage equal to that of the main element, wherein a negative pole of the main element is connected to a negative pole of the auxiliary element to define the positive pole of the main element as a positive pole terminal and the positive pole of the auxiliary element as a negative pole terminal, and the high-speed freewheel diode is parallel-connected between the positive pole terminal and the negative pole terminal so that a direction from the negative pole terminal toward the positive pole terminal constitutes a forward direction.

Abstract: An electric power conversion system includes a DC power supply, plural main circuit switching devices bridge-connected to carry out DC/AC convert, having freewheeling diodes connected in reverse parallel thereto, respectively, and a reverse voltage application circuit for applying a reverse voltage smaller than the DC power supply to each freewheeling diode, upon a cutoff of back-flow current of the freewheeling diode, the reverse voltage application circuit being composed of a series connection of a low-voltage DC power supply, a reverse voltage application switching device having a lower withstand voltage than the main circuit switching devices and adapted to turn on upon a reverse recovery of the freewheeling diode, and an auxiliary diode having a shorter reverse recovery time than the freewheeling diode, the reverse voltage application switch being a device having holes as a majority carrier.