Automatic phase control apparatus

摘要

An automatic phase control apparatus for controlling the frequency of a sine wave produced from a variable frequency oscillator to be equal to that of the carrier wave of the extracted chrominance signal. A phase difference detector 4 detects a phase difference between the sine wave and the carrier wave. The detected phase difference is integrated to obtain an integrated value which is applied to the frequency oscillator for determining the oscillation frequency. A deviation detector is provided for detecting a deviation of the integrated value with respect to an expected frequency control data calculated by a calculator. When the deviation is greater than a predetermined range, the integrated value is replaced with the calculated data.