Patent ID: 8240425
Filing Date: 2012-08-14
Classification: B62D,H02M

Abstract:
1. An electric power steering apparatus for generating a steering assist force by a motor, comprising: a battery for supplying an electric power to the motor; an auxiliary power supply connected in series with the battery and capable of supplying an electric power to the motor; a charge circuit powered by the battery and serving to charge the auxiliary power supply; a motor driving circuit for driving the motor; a first switching device interposed in a first electrical conduction path for conducting a voltage of the battery to the motor driving circuit; a second switching device interposed in a second electrical conduction path at a place upstream of a junction of the first and second electrical conduction paths, the second electrical conduction path serving to conduct a voltage of the series-connected battery and auxiliary power supply to the motor driving circuit and joining the first electrical conduction path at a place downstream of the first switching device; a voltage detector for detecting a potential difference across at least one of the first switching device and the second switching device; and a control circuit for controlling the first switching device and the second switching device in response to a required steering assist force to thereby turn off either one of the first and second switching devices and turn on the other switching device, the control circuit issuing a failure signal upon determination that the one switching device is damaged in a case where the auxiliary power supply has a voltage equal to or more than a given value and a potential difference across the one switching device is equal to or less than a predetermined value when the other switching device is on.