Servo control system for disk player

Claim 2

A rotation servo circuit (18) for use in a disk player having a bulk memory (23) of a large capacity for storing the data read from a disk (1), and a memory control means (22) for monitoring the data quantity stored in said bulk memory (23) and outputting an overflow signal when the data quantity has exceeded a preset value, said rotation servo circuit (18) functioning to control the rotation speed of the disk (1) in such a manner that the disk is driven normally in a low speed mode but is driven in a high speed mode upon occurrence of a track jump, and thereafter the disk (1) is driven in the low speed mode again when said overflow signal is outputted, said rotation servo circuit (18) comprising: a clock generator means (17) for generating a first clock signal of a predetermined frequency; a frequency divider means (32) for outputting a second clock signal by dividing the frequency of said first clock signal at a predetermined fixed ratio; and a gate means (31, 33-35) for selectively outputting said second clock signal in the low speed mode or said first clock signal in the high speed mode; wherein the operation of driving the disk (1) is controlled on the basis of the clock signal outputted from said gate means (31, 33-35).

Claim 3

A rotation servo circuit (18) for use in a disk player having a first servo circuit (60) for detecting the speed difference between the rotation speed of a disk (1) and a reference speed thereof and then controlling the rotation of the disk (1) in accordance with the detected speed difference, and a second servo circuit (70) of a secondary loop structure which consists of a phase loop (71, 73) for detecting the phase difference between a reproduced sync signal (WFCK) obtained from the disk (1) and a reference sync signal (RFCK) and then controlling the rotation of the disk in accordance with the detected phase difference, and a speed loop (72, 74) for measuring the period of the reproduced sync signal (WFCK) and controlling the rotation of the disk on the basis of the measured period, wherein the rotation control by said second servo circuit (70) is executed posterior to completion of the rotation control by said first servo circuit (60), and at the time of reading the recorded data from the disk (1) by an optical pickup (3), both of said phase loop and said speed loop are closed to execute the rotation control; wherein, at the time of a seek, said optical pickup (3) is displaced in the radial direction of the disk (1) in a state where said second servo circuit (70) is turned off while said first servo circuit (60) is turned on, and after a certain displacement of said optical pickup (3) corresponding to a predetermined number of tracks, the position data are read from the disk in a state where said first servo circuit (60) is turned off while only the speed loop (72, 74) of said second servo circuit (70) is closed, and a series of such operations are repeatedly executed until arrival of said optical pickup (3) at its desired target position.

Claim 4

A disk player comprising: a signal processor means (10) for processing a reproduced signal obtained from a disk (1), then detecting the phase difference between the rotation speed of the disk and a desired rotation speed thereof, and outputting a speed control signal corresponding to the detected speed difference; an oscillator means (88) for supplying an oscillation output as a system clock signal to said signal processor means (10), wherein the frequency (Fa) of said oscillation output is varied in accordance with said speed control signal; and a speed control means (91-93) for detecting the phase difference between said oscillation output and a reference clock signal, and controlling the rotation speed of the disk (1) in accordance with the detected phase difference.

Claim 5

The disk player according to claim 4, wherein said speed control means comprises a first frequency divider means (91) for dividing the frequency (Fa) of said oscillation output at a variable ratio (M); a second frequency divider means (93) for dividing the frequency (Fb) of said reference clock signals at a variable ratio (N); and a phase comparator means (92) for detecting the phase difference between the respective outputs of said first and second frequency divider means (91, 93) by comparing the phases of such two outputs with each other.

Claim 6

The disk player according to claim 4 or 5, further having a selector means (89) for selecting either said oscillation output or said reference clock signal and supplying the selected one as a system clock signal to said signal processor means (10).