| 摘要 |
PROBLEM TO BE SOLVED: To provide a motor having a good power efficiency for rotatably driving at a low vibration and low noise in a predetermined direction without using a position detecting element and a disc device. SOLUTION: A power transistor of a power supply unit 20 forms a current path to three-phase coils 11, 12, 13 while high-frequency switching. A voltage detector 30 detects PWM modulated terminal voltages V1, V2, V3 of the coils 11, 12, 13, and outputs a detected pulse signal Dt responsive to the terminal voltages. A state transition unit 31 transits a holding state in response to an edge generation of the pulse signal after a first regulating time and a second regulating time and outputs a state signal. A switching controller 22 forms a PWM pulse signal in response to a compared result of a current direction signal with a command signal. A current supply controller 32 switches ON and OFF of a power transistor at high frequency in response to the output signals of the unit 31 and the controller 22. A voltage detector 30 stops or executes detection of the terminal voltage in response to the PWM operation of the controller 22 to prevent an erroneous detection due to a PWM noise. |
