| 摘要 |
PURPOSE:To reduce a noise at phase switching time by setting the rising and falling characteristics of a switching signal for switching the phase to a motor coil in response to the rotating speed of a motor to the desired value. CONSTITUTION:Rotor position detection signals from Hall elements P1-P3 are supplied through amplifiers 1-3 to a matrix circuit 4. The circuit 4 outputs a switching signal for switching the phase on the basis of the position detection signal. Diodes D1-D3 respectively generate voltages proportional to the counterelectromotive voltages of motor coils L1-L3. The voltages are altered in response to the rotating speed of the motor, and the amplification factors of the amplifiers 1-3 are controlled by the voltages. |
