Brushless motor and disk drive apparatus

Abstract

A brushless motor has first and second power transistors which form current paths to three-phase windings so as to rotate a rotor. A position detecting part produces a position signal in response to a rotation of the rotor. An activation operation block controls active operation of the first and second power transistors in response to the position signal. The activation operation block includes a starting operation part which comprises an initial phase setting part, phase changing part and a phase correcting part. The initial phase setting part sets an initial phase of drive signals to the three-phase windings in response to the level of the position signal at the timing of a start signal. The phase changing part changes sequentially the phase of the drive signals to the three-phase windings in the positive direction in response to time. The phase correcting part corrects the phase of the drive signals to the three-phase windings in response to the occurrence of the rising and falling edges of the position signal. Therefore, the brushless motor with reduced position sensor can stably start the rotation of the rotor by using one position signal of one position sensor.