| 摘要 |
A microcomputer calculates a command value for feedback control based on a target electric current value set on the basis of steering torque and a vehicle speed, and the detecting value of a motor electric current. The microcomputer calculates the duty ratio of a PWM signal for turning on and off a switching element of a motor driving circuit from this command value. When this calculated duty ratio is 100% or less, no voltage raising circuit is operated and a battery voltage is supplied to the motor driving circuit. In contrast to this, when the calculated duty ratio Dc exceeds 100%, the microcomputer outputs the PWM signal for turning on and off the switching element of the voltage raising circuit in the duty ratio according to this excess amount. Thus, the battery voltage is raised in accordance with this excess amount and is supplied to the motor driving circuit. <IMAGE>
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