| 摘要 |
PROBLEM TO BE SOLVED: To secure both the speed and stability of locking by selecting and using error signals whose duty factors are different in accordance with a phase pulling stage. SOLUTION: 1st and 2nd pulse generating parts 7 and 8 in a phase difference detector 3 respectively generate pulse trains according to comparison results of a phase comparing part 1. A selector 9 selects one between them according to a control signal. For instance, the part 7 generates a cyclic pulse whose duty factor is small and the part 8 generates a cyclic pulse whose duty factor is large. When power is inputted or when the circuit is started from an input clock disconnection state, phase pulling control is performed with a pulse with a large duty factor. Since a voltage controlled oscillator 5 operates in accordance with the integration of an error signal outputted from the part 1, even though the locking speed increases in such a case, pulling stability is sacrificed. Once locking is completed, control is performed with a pulse with a small duty factor to increase stability. |
