| 摘要 |
PURPOSE:To obtain an accurate synchronizing signal regardless of a secular change or an effect of an ambient temperature by comparing a self-running frequency from a VCO with a reference self-running frequency so as to control the VCO. CONSTITUTION:A reproduction signal from an optical disk is binarized and the phase is compared with a clock outputted from a VCO 7 at a phase comparator circuit 4 and the VCO 7 is subject to PLL control in response to a phase deviation via a charge pump circuit 5 and a synchronizing signal synchronously with a binarized signal is outputted. When the signal is not reproduced and no binarized signal is inputted to the circuit 4, the VCO 7 outputs a self-running frequency and the frequency is counted by a frequency counter 1 and compared with a reference frequency at a frequency comparator circuit 2, the VCO 7 is controlled in response to the result of comparison and the VCO 7 outputs the self-running frequency signal with a prescribed frequency independently of a secular change or an effect of an ambient temperature at all times. Thus, the accurate synchronizing signal is always obtained independently of a secular change or an effect of an ambient temperature. |
