Frequency stabilized clock signal generator synchronized to an input

Abstract

A synchronizing clock generating circuit for generating synchronizing clocks timed to synchronizing signals contained in input video signals is disclosed. A trapezoidal wave from a trapezoidal wave generator 19 and a reference pulse RP from a reference pulse generator 12 are compared as to phase in a phase comparator 21, while the trapezoidal wave and a pseudo-reference pulse rp from a CH2 generator 23 are compared as to phase in a phase comparator 22, and a difference between outputs of phase comparison is used in a dc detection circuit 24 for controlling the gradient of the trapezoidal wave. Besides, an output of a VCO 15, controlled by the results of phase comparison between the trapezoidal wave and the reference pulse RP is used as a synchronizing clock signal. In this manner, the synchronizing clock signal is stabilized in frequency, while frequency deviations produced by temporal changes in component parts or temperature characteristics may be corrected to prevent deteriorations, such as bends or distortions, from being produced in the reproduced picture, for improving the picture quality.