Patent ID: 7529331

Claim:
A clock generator being applied to a DVD optical drive for generating a non-phase-modulated target clock signal based on a phase-modulated input signal, the clock generator comprising: an arithmetic/logic circuit for calculating a period count value by counting a period of the input signal according to a reference clock having a predetermined frequency, calculating an average period value by averaging a plurality of the period count values, and comparing the average period value with the period count value for outputting a first control signal; and a phase-locked loop connected to the arithmetic/logic circuit for generating the target signal according to the first control signal and the input signal, feeding the target signal back to the input of the phase-locked loop, and determining whether the target clock signal is to be synchronized with the input signal based on a logic level of the first control signal, the phase-locked loop comprising: a phase-frequency detector connected to the arithmetic/logic circuit configured to generate a second control signal by comparing the target clock signal with the input signal and to determine whether the second control signal is outputted according to the logic level of the first control signal; a loop filter connected to the phase-frequency detector configured to generate a control voltage based on the second control signal; and a voltage-controlled oscillator connected to the loop filter configured to control the frequency of the target clock signal based on the control voltage; wherein when the first control signal corresponds to a first logic level, the phase-locked loop compares the target clock signal with the input signal to drive the target clock signal to be synchronized with the input signal, and when the first control signal corresponds to a second logic level, the phase-locked loop holds the target clock signal without driving the target clock signal to be synchronized with the input signal.