PLL circuit and disk drive
AssigneeNEC Corporation
InventorHiromi Honma
Life of this patent
Estimating the term…
Abstract
A digital loop filter receives a phase error output from a phase comparator to generate a digital frequency value. This digital frequency value is converted into an analog voltage by a D/A converter, and VCO outputs a synchronizing dock of frequency corresponding to the voltage output from the D/A converter. The phase error output from a phase comparator is gain-corrected by a product of an output from the digital loop filter and a specific coefficient “A”, and delivered to digital loop filter. The phase error input to the digital loop filter is changed in proportion to the output clock frequency, whereby the PLL loop as whole linearly controls the loop characteristic depending on the output clock frequency.
Claims11
A PLL circuit that extracts a synchronizing clock from an analog signal in which a channel frequency changes, said PLL circuit comprising:
- a phase synchronization loop having a loop gain and comprising:
- an A/D converter that converts the analog signal into a digital signal;
- a digital phase comparator that operates in synchrony with the synchronizing clock to output a phase error signal between the analog signal and the synchronizing clock based on the digital signal output from said A/D converter;
- a digital loop filter that operates in synchrony with the synchronizing clock to output a digital frequency value proportional to the channel frequency based on the phase error signal;
- a D/A converter that converts said digital frequency value into an analog frequency signal and outputs the analog frequency signal;
- and an oscillator that outputs the synchronizing clock having a frequency controlled based on the digital frequency value;
- and
- a loop-gain control unit that controls the loop gain of said phase synchronization loop based on said digital frequency value which is converted into said analog frequency signal by said D/A converter,
- wherein said loop-gain control unit comprises a multiplier that multiplies the phase error signal output from said digital phase comparator by a value corresponding to the digital frequency value output from said digital loop filter to output the multiplied value to said digital loop filter, said multiplier being provided between an output side of the digital phase comparator and an input side of the digital loop filter.
A disk drive that reproduces data from a disk by using a CAV (constant angular velocity) control technique, comprising:
- a phase synchronization loop having a loop gain and comprising:
- an A/D converter that converts into a digital readout signal a readout signal obtained by reading information recorded on the disk;
- a digital phase comparator that operates based on a synchronizing clock extracted from the readout signal to output a phase error signal between the readout signal and the synchronizing clock based on the digital readout signal;
- a digital loop filter that operates based on the synchronizing clock to output a digital frequency value in proportion to a channel frequency of the readout signal based the phase error signal;
- a D/A converter that converts said digital frequency value into an analog frequency signal and outputs the analog frequency signal;
- and an oscillator that outputs the synchronizing clock having a frequency controlled based on the digital frequency value;
- a loop-gain control unit that controls the loop gain of said phase synchronization loop based on said digital frequency value which is converted into said analog frequency signal by said D/A converter;
- and
- a data demodulator that operates based on the synchronizing clock to identify data from the digital readout signal,
- wherein said loop-gain control unit comprises a multiplier that multiplies the phase error signal output from said digital phase comparator by a value corresponding to the digital frequency value output from said digital loop filter to output the multiplied value to said digital loop filter, said multiplier being provided between an output side of the digital phase comparator and an input side of the digital loop filter.
A disk drive that records data on an optical disk by using a CAV (constant angular velocity) control technique, comprising:
- a phase synchronization loop having a loop gain and comprising:
- an A/D converter that converts into a digital wobble signal a wobble signal that is read from the disk;
- a digital phase comparator that operates based on a clock extracted from the wobble signal to output a phase error signal between the wobble signal and a synchronizing clock based on the digital wobble signal;
- a digital loop filter that outputs a digital frequency value that is in proportion to a frequency of the wobble signal;
- a D/A converter that converts said digital frequency value into an analog frequency signal and outputs the analog frequency signal;
- and an oscillator that outputs the synchronizing clock having a frequency controlled based on the digital frequency value, said phase synchronization loop multiplying the clock signal to generate a recording clock;
- and
- a loop-gain control unit that controls the loop gain of said phase synchronization loop based on said digital frequency value which is converted into said analog frequency signal by said D/A converter,
- wherein said loop-gain control unit comprises a multiplier that multiplies the phase error signal output from said digital phase comparator by a value corresponding to the digital frequency value output from said digital loop filter to output the multiplied value to said digital loop filter, said multiplier being provided between an output side of the digital phase comparator and an input side of the digital loop filter.
Dependencies are inferred from the claim text.