Pulling-in circuit for PLL circuit, pulling-in method for PLL circuit, PLL circuit device and apparatus for reproducing optical disc

A pulling-in method for a PLL circuit to which an input signal is inputted, said PLL circuit comprising:

• a voltage controlled oscillator for outputting an output signal;
• a control voltage generation circuit for generating a control voltage to lock phases of the input and output signals by a loop, and outputting the generated control voltage to a control input terminal of said voltage controlled oscillator;
• and a central frequency setting circuit for setting a central frequency, to which a frequency of the output signal is to be pulled-in, to said control voltage generation circuit, said pulling-in method comprising the steps of:
• setting a sweep range, where the frequency of the output signal is to be pulled-in to the set central frequency, on the basis of the set central frequency;
• detecting whether or not a pulling-in operation is completed in said PLL circuit, and outputting a lock signal when the pulling-in operation is detected to be completed;
• and
• controlling said control signal generation circuit to generate the control signal to repeatedly sweep the frequency of the output signal through the set sweep range during the pulling-in operation until the lock signal is outputted.

A PLL circuit device comprising a PLL circuit, to which an input signal is inputted, and a pulling-in circuit,

• said PLL circuit comprising:
• a voltage controlled oscillator for outputting an output signal;
• a control voltage generation circuit for generating a control voltage to lock phases of the input and output signals by a loop, and outputting the generated control voltage to a control input terminal of said voltage controlled oscillator;
• and a central frequency setting circuit for setting a central frequency, to which a frequency of the output signal is to be pulled-in, to said control voltage generation circuit,
• said pulling-in circuit comprising:
• a sweep range setting circuit for setting a sweep range, where the frequency of the output signal is to be pulled-in to the set central frequency, on the basis of the set central frequency;
• a lock detector for detecting whether or not a pulling-in operation is completed in said PLL circuit, and outputting a lock signal when the pulling-in operation is detected to be completed;
• and
• a sweep range control circuit for controlling said control signal generation circuit to generate the control signal to repeatedly sweep the frequency of the output signal through the set sweep range during the pulling-in operation until the lock signal is supplied thereto.