Phase-synchronous controller for production of reference clock signal in optical disk drive system.

摘要

A phase-lock control circuit (20) suitable for an optical disk apparatus of a sample-servo format scheme includes an injection-synchronized control loop in addition to a normal phase-lock loop control loop. The phase-lock loop control loop includes a phase-comparator (24), a low-pass filter (26), a voltage-controlled oscillator, i.e. a VCO (27), a frequency-dividing counter (28), and a decoder (29). The phase-comparator (24) detects a phase difference between a clock pit pulse signal (Pin) and a feed-back pulse signal (Pfb) supplied through the frequency-dividing counter (28) and the decoder (29). The VCO (27) is oscillated to compensate for the phase difference and generates a reference clock signal (Pck). A time-base filter (30) and an injectdion pulse generator (31) are provided for the VCO (27) to constitute the injection-synchronized control loop, wherein at least one injection pulse (Pi) having a pulse width substantially equal to the non-response period of the comparator (24) is intermittently generated in response to the reference clock signal (Pck) upon completion of a comparison operation by the comparator (24), and the injectdion pulse is supplied to the VCO (27). The VCO (27) is of an injection-synchronized voltage-controlled type.