Patent ID: 7122980

Claim:
A motor driving apparatus which drives a motor having windings of a plurality of phases and a rotor in a sensor-less control, comprising: a comparator operable to compare an induced voltage generated in a motor winding of a non-conduction phase with a predetermined threshold; a threshold controller operable to control the threshold; a position determining unit operable to determine a rotor position based on an output from the comparator; a phase-switching controller operable to switch a conduction phase in response to the rotor position; and a current output unit operable to generate a current used for driving the motor and to supply the current to the conduction phase, wherein: the phase-switching controller supplies a predetermined phase of winding with a current pulse having a predetermined pulse width so as not to cause the rotor to react and operate in order to determine the initial position of the rotor, while the rotor is stopped; the position determining unit determines an initial position of the rotor based on the result of comparison between the induced voltage generated in a non-conduction phase by supplying the current pulse and the threshold; and the phase-switching controller performs energization according to the determined initial position of the rotor to start up the motor.