Patent ID: 7970254
Filing Date: 2011-06-28
Classification: G11B,H03L

Abstract:
1. A PLL control circuit of an optical disc apparatus comprising: a voltage frequency conversion circuit that adjusts an oscillating frequency based on a control voltage to generate a first frequency signal; a phase comparison circuit that compares the phase of the first frequency signal with the phase of a second frequency signal generated based on an RF (Radio Frequency) signal at the time of photoelectric conversion of reflected light of the laser beam applied to an optical disc, to generate a phase difference signal indicating a phase difference between the first frequency signal and the second frequency signal; a charge pump circuit that generates the control voltage for synchronizing the phases of the first frequency signal and the second frequency signal according to the phase difference signal; a first detection circuit that detects whether the RF signal exceeds a predetermined level; a second detection circuit that detects whether the phases of the first frequency signal and the second frequency signal are synchronized; and a control circuit that controls the charge pump circuit; to generate the control voltage regardless of the phase difference signal, if the first detection circuit detects that the RF signal exceeds the predetermined level, and to generate the control voltage according to the phase difference signal, if the second detection circuit detects that the phases of the first frequency signal and the second frequency signal are synchronized.