| 摘要 |
PURPOSE:To suppress mechanical noise without requiring capacitor and to facilitate miniaturization by a constitution wherein a PWM duty control means for controlling a stepwise waveform to be applied on a coil according to an input pulse is provided and the current flowing through the coil is switched to control the rotational movement time. CONSTITUTION:A speed pulse signal SP, i.e., an input signal, is fed to a PWM control step signal generating circuit 14. A stepwise waveform produced from the circuit 14 is subjected to PWM control for its switching timing to vary the duty value. PWM duty for a predetermined PWM period T1 varies such that the pulse width increases gradually as shown by the waveforms W1-W5 of G1 or decreases gradually as shown by the waveform of G2. Consequently, variation of current value has gentle inclination and the currents flowing through coils 12, 13 can be switched in (arrowa E, F) directions with no abrupt variation. |
