| 摘要 |
PROBLEM TO BE SOLVED: To resolve problems that, at a turn-off operation of a group of at least three series-connected switch elements that has a function of maintaining an on state and an off state simultaneously in a multilevel conversion circuit to which a switch element series circuit obtained by series-connecting at least eight switch elements between a positive electrode and a negative electrode of a DC power supply is connected, a voltage applied to a switch element that is firstly cut off becomes large, and that an element with a high withstanding voltage is required, which causes increase in size and cost of a device.SOLUTION: At a turn-off operation of a group of at least three series-connected switch elements, a voltage clamp circuit is connected between a collector and an emitter or between the collector and a gate of only one switch element of the series-connected switch elements. This switch element is firstly cut off, and thereafter, the remaining switch elements are cut off after a predetermined time period. |
