Patent ID: 7615959

Claim:
A control apparatus for a brushless DC motor, which has a rotor with n poles (where n is a natural number) that performs an operation of rotating or stopping due to a supply current with m phases (where m is a natural number) applied to a stator, controlling a number of output rotations of a gearbox, which is connected to the brushless DC motor and has a predetermined gear reduction ratio, the gear reduction ratio representing a ratio of a number of rotations of the brushless DC motor to the number of output rotations of the gearbox, the control apparatus comprising: a rotation detector part, which obtains a detected number of rotation pulses generated by the rotation of the rotor from the brushless DC motor; a required rotational amount input part, which receives a number of output rotations as input and converts it to a corresponding required number of rotation pulses; a comparison part, which compares the detected number of rotation pulses and the required number of rotation pulses; and a current controller part, which controls the supply current applied to the brushless DC motor according to a comparison result of the comparison part, the supply current being one of a first supply current and a second supply current, the current controller part applying the first supply current to the brushless DC motor when the detected number of rotation pulses is smaller than the required number of rotation pulses and applying the second supply current to the brushless DC motor when the detected number of rotation pulses is equal to the required number of rotation pulses, the brushless DC motor rotating at constant speed when the first supply current is applied and stopping when the second supply current is applied, wherein the brushless DC motor is a sensorless type, and the rotation detector part counts a total number of detections of counter electromotive force generated in a multiphase coil of the stator as the number of rotation pulses.