Patent ID: 6873125

Claim:
A motor driving apparatus comprising: (a) a first driver formed of a plurality of driving elements which are coupled to both a driving coil of a motor and a first power-supply line; (b) a second driver formed of a plurality of driving elements which are coupled to both the driving coil of the motor and a second power-supply line; (c) a position detector for detecting a positional relation between a rotor magnet of the motor and the driving coil; (d) a conduction switch for outputting a conduction switching signal to the driving coil based on a detection signal supplied from the position detector; (e) a torque instructor for outputting a torque instructing signal for regulating torque generated by the motor; (f) a pulse-width modulator for outputting a frequency signal having a duty of a pulse width in response to the torque instructing signal; (g) a PWM controller for controlling ON/OFF of the plurality of driving elements included in the first driver and the second driver in response to an output signal from the conduction switch and an output signal from the pulse-width modulator; (h) a driving-state detector for detecting at least one of an acceleration mode, a deceleration mode, and a regular rotation mode of the motor being driven; and (i) a PWM frequency switch for switching a carrier frequency of the pulse-width modulator based on an output from the driving-state detector, wherein the carrier frequency is set at a lower level in a start-up period of the motor than in a regular rotation period.