| 摘要 |
PROBLEM TO BE SOLVED: To prevent the radiation of high frequency noise in an unstable state when power is supplied by holding a phase comparison output signal so that VCO output frequency becomes low for a while after power is supplied by means of a power-on reset signal and the like. SOLUTION: The power-on reset signal is given for a while after power is supplied as the control signal Vc of a phase comparator PD. When the control signal Vc is active, phase difference signals Vn and Vp are continued to be outputted in a direction where the frequency of the output signal fout of a voltage control oscillator VCO becomes the lowest. A signal outputted by the judgment of a microcomputer is used as the control signal Vc . In such a case, the VCO output signal fout is kept to be the lowest even if the reference signal Vs is lacked. Thus, the wasteful power consumption of a servo control system and a system control system, which input the output signals of a PLL circuit, can be reduced. |
