| 摘要 |
A PWM-signal-output circuit includes a detecting unit to detect periods in which a speed signal with logic level changing alternately and having a period corresponding to a motor-rotation speed is at one and the other logic levels, a dividing unit to divide each of the periods into first to third periods; a first output unit to change a PWM-signal duty-cycle in a stepwise manner toward an input-signal duty-cycle in the first period, a second output unit to cause a PWM-signal duty-cycle to become equal to an input-signal duty-cycle, to maintain a current flowing through the motor coil constant, in the second period; and a third output unit to change a PWM-signal duty-cycle in a stepwise manner from an input-signal duty-cycle, to decrease a current flowing through the motor coil, in the third period.
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