| 摘要 |
PROBLEM TO BE SOLVED: To enable the complete and quick stoppage of a spindle motor by applying the brakes to a rotating spindle motor from a time when a stopping signal is outputted till a time when a stop predicting time is elapsed. SOLUTION: A multiplexer 5 selectively outputs either a sensor signal 12 or a synchronizing signal 11 by a multiplexer control signal supplied from an operation processor 8. A period measuring counter 7 obtains the linear velocity of a disk 1 or the rotational speed of a spindle motor 2 by counting the interval between rising edges of the input signal of the counter with a clock generated by a counter clock 6. The operation processor 8 reads in the count data of the counter and obtains speed error data in comparison with target speed data by calculating deviations from target values set in the processor so that a controlled variable is outputted to an analog-to-digital converting circuit 9. A motor driving circuit 10 applies an acceleration current in a normal direction of rotation when the voltage of an analog controlled variable is smaller than a reference voltage, and the acceleration current in the reverse direction of rotation when the voltage of the analog control variable is larger then the reference voltage.
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