Electric power steering apparatus and control method therefor

A control method for an electric power steering apparatus for generating a steering assist force by a motor, wherein the electric power steering apparatus includes a motor drive circuit for driving the motor, a battery capable of supplying electric power to the motor, an auxiliary power supply capable of supplying electric power to the motor, and a charge-discharge circuit that configures a circuit for charging the auxiliary power supply and a circuit for discharging the auxiliary power supply, the charge-discharge circuit being capable of configuring a discharge-preference circuit that enables only the discharge of the auxiliary power supply while avoiding the charge thereof, the control method comprising:

• controlling the charge-discharge circuit and also controlling the motor drive circuit in response to a required steering assist force;
• and
• performing a power latch operation of carrying on the control till the end of a predetermined period of time following an operation of turning off an ignition key and also causing the charge-discharge circuit to configure the discharge-preference circuit thereby enabling steering assist accompanied by the discharge of the auxiliary power supply.