| 摘要 |
PURPOSE: A synchronizing band changer of a PLL(phase locked loop) is provided to equalize the phase of a clock signal outputted from a VCO(voltage controlled oscillator) with a reproduced signal having a large variable band read out of a DVD(digital video disk) or CD(compact disk). CONSTITUTION: A synchronizing band changer of a PLL adopts an offset voltage generator(24). The offset voltage generator obtains a phase difference signal of a clock signal outputted from a VCO and a reproduced signal having a large variable band read out of a DVD or CD. The offset voltage generator converts the reproduced signal and phase difference signal into DC signals and controls the oscillation frequency band of the clock signal depending on the signal level of the converted DC signals. The synchronization band changer of the PLL equalizes the phase of the clock signal with the reproduced signal of the DVD or CD through the offset voltage generator. Therefore, the synchronization band changer prevents load of a microcomputer. Herein, the microcomputer calculates the size of offset voltage corresponding to the rotational speed of an optical disk.
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