Patent ID: 7679944

Claim:
A motor drive comprising: an arm which has an upper arm section and a lower arm section, the upper arm section includes a first electric power semiconductor-switching element and the lower arm section includes a second electric power semiconductor-switching element, both upper and lower arm sections and first and second electric power semiconductor-switching elements are connected in series between major terminals; and a level-shifting circuit which transmits a control signal of the first electric power semiconductor-switching element connected to a high-voltage side of the arm, from a low-voltage circuit to a high-voltage circuit; wherein the motor drive has a circuit composition in which a difference between a grounding voltage of the lower arm section and a grounding voltage of the upper arm section is equal to ΔV 1 +ΔV 2 , generated by a change of current and a wiring inductance at a transitional period ON/OFF of the upper arm section first electric power semiconductor-switching element which exceeds an operating voltage HVcc of a control power supply for controlling the first electric power semiconductor-switching element of the upper arm section; wherein ΔV 1 is a voltage change caused by a time change dI 1 /dt from a maximum value of a current in the lower arm second electric power semiconductor-switching element to a steady current and by a wiring inductance in the lower arm section; wherein ΔV 2 is a voltage change caused by a decrement dI 2 /dt in a recovery current of the upper arm first electric power semiconductor-switching element and by a wiring inductance in the upper arm section; and wherein a signal-transmitting high-withstand-voltage element in the level-shifting circuit is an insulated-gate bipolar transistor.