Patent ID: 8823302

Claim:
A control apparatus for a switching circuit that includes a plurality of bidirectional conduction switching devices connected in series to each other and a plurality of reverse conducting devices respectively connected in parallel to the bidirectional conduction switching devices with respect to forward conduction of the bidirectional conduction switching devices, and that is configured to perform power conversion between a direct current power source and an alternating current motor, the control apparatus comprising: a controller configured to turn on the bidirectional conduction switching device provided parallel to the reverse conducting device through which a commutation current flows; a target-rotational-speed acquiring device configured to acquire a target rotational speed of the alternating current motor; a target-torque acquiring device configured to acquire a target torque of the alternating current motor; and an ON-time varying device configured to vary, in a current area in which conductive loss of the bidirectional conduction switching is greater than conductive loss of the reverse conducting device, on a basis of the target rotational speed and the target torque, an ON time period during which the bidirectional conduction switching device is turned on when the commutation current flows through the reverse conducting device such that the commutation current flows through both the bidirectional conduction switching device and the reverse conducting device which are connected in parallel to each other, the ON-time varying device being configured to decrease the ON time period with an increase in the forward conduction in accordance with an increase in the target rotational speed and configured to decrease the ON time period with an increase in the forward conduction in accordance with an increase in absolute value of the target torque in which powering is set to positive and regeneration is set to negative.