| 摘要 |
A spindle servo circuit in an optical disc reproducing apparatus operates with enhanced stability at disc rotation speeds substantially higher than normal. The spindle servo circuit includes a first phase comparator which compares the phases of a reference clock signal and a reproduced frame clock signal and outputs a phase difference signal. The spindle servo circuit also includes a first low pass filter for generating a revolution speed control signal for a spindle motor by low-pass filtering the phase difference signal. The revolution speed control signal is input to a motor driving means for driving revolution of a spindle motor, which in turn spins the optical disc. Optical signals are picked up off the disc and run through a high frequency amplifier for amplifying and wave-shaping to produce a reproduction data signal. A phase locked loop circuit generates a reproduced bit clock signal from the reproduced data signal during normal operation, and during high speed operation (above a predetermined speed) generates the reproduced bit clock signal corresponding to a previous state. Thereby, in the spindle servo control system for operating at higher than normal speed, according to the present invention, the servo control system can be maintained in a stable state by fixing the phase synchronous loop of an accurate servo control system at a predetermined high speed, to allow stable restoration of data when operating at high speed.
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