| 摘要 |
A motor-driven power steering apparatus includes a motor for generating assisting force to be imparted to a steering mechanism, a control signal generation section for generating a motor control signal on the basis of at least steering torque applied to a steering wheel, a motor drive unit for driving the motor in accordance with the motor control signal, and a step-up circuit provided between a battery to the motor drive unit. The step-up circuit includes a step-up coil whose one end is connected to the battery, a first switching element connected between the other end of the step-up coil and the ground, a second switching element connected between the other end of the step-up coil and an output terminal, and a capacitor connected between the output terminal and the ground and smoothing output voltage appearing at the output terminal. The apparatus further includes a step-up circuit control unit which detects the output voltage and controls the first and second switching elements on the basis of difference between a target output voltage and the detected output voltage. During power generation periods, at least the first switching element is turned on and off in order to increase the output voltage supplied to the motor through step-up operation. During regeneration periods, at least the second switching element is turned on and off.
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