| 摘要 |
PURPOSE:To simplify the constitution of a circuit and to stabilize an action by varying gains according to the period or frequency of a pulse outputted from a frequency signal generator which outputs a signal with a frequency corresponding to the rotating frequency of a disk. CONSTITUTION:A counter 15 counts the frequency of the pulse outputted from the frequency signal generator 3 with the aid of a clock signal with a fixed frequency from a reference clock signal generator 18. In synchronization with the pulse outputted from the frequency signal generator 3, a latch circuit 16 latches the count value CN of the counter 15. Based on the count value CN, a PWM circuit 17 PWM-controls a switch 12, controls the transmission from a phase comparator 11 to an LPF 13 to be turned on or off, an outputs the effect to a drive circuit 14. Since the detection sensitivity of the disk 1 is in proportion to a radius, gains from the input of the switch 12 to the output of the LPF 13 does not depend on the radius (r) but becomes constant, thereby stabilizing a phase control system.
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