| 摘要 |
PURPOSE: To speedily make a response to the switching of an input video signal by generating a frequency-dividing ratio based on the integral value of a phase comparison error between a reference input signal and a comparison signal. CONSTITUTION: When the reference input signal is switched, the comparison signal of a frequency nearest to the frequency of the reference input signal is generated. When the reference input signal is switched in such a case, a programmable frequency-dividing part 2 becomes the output state of the minimum frequency signal (reference signal) by the prescribed frequency-dividing ratio, for example. An A/D conversion part 5 generates voltage data obtained by converting the comparison error integral value (control voltage) of LPF 4 controlling VCO 1 into digital data and supplies it to ROM 7. ROM 7 refers to a look-up table where the comparison error integral value is made to correspond to frequency-dividing ratio, reads corresponding frequency-dividing ratio and supplies the frequency-dividing ratio data to the frequency-dividing part 2 via a control part 8. When various video signals are switched and inputted, the signal locked to the phase of the reference input signal can be generated at high speed. |
