Patent ID: 6885252

Claim:
A clock recovery circuit capable of automatically adjusting a central frequency of a voltage-controlled oscillator, comprising: a phase detector for receiving an input signal and a VCO clock and outputting a control signal according to phase difference between the input signal and the VCO clock; a charge pump for controlling charge action according to the control signal outputted from the phase detector; a loop filter connected to the charge pump and in cooperation with the charge pump to output a voltage signal; a voltage-controlled oscillator for receiving the voltage signal from the loop filter and a control voltage for controlling the central frequency and outputting the VCO clock according to both the voltage signal and the control voltage; a frequency counter for receiving the VCO clock, counting the frequency of the VCO clock and outputting an oscillation frequency value; and a frequency control unit for receiving the oscillation frequency value, setting an updated central frequency value according to the oscillation frequency value and a current central frequency value, and outputting the control voltage corresponding to the updated central frequency value to the voltage-controlled oscillator, so that the central frequency of the voltage-controlled oscillator is automatically adjusted in an online manner, such that the updated central frequency value is closer to the frequency of the VCO clock than the current central frequency value.