JPS6429175A - Synchronizing signal generation circuit in television receiver - Google Patents

Abstract

PURPOSE:To enable a synchronizing signal with high stability to be generated by detecting the cycle of a separated synchronizing signal from it, smoothing the fluctuation part of the cycle, eliminating the fluctuation part when it is bigger than a threshold and generating the synchronizing signal based on the cycle of the smoothed synchronizing signal. CONSTITUTION:A compound video signal 1 is inputted to a horizontal synchronizing separator circuit 2 and the digital data of the cycle detected by a cycle detection circuit 5 is inputted to a smoothing circuit 6 and smoothed. The smoothed cycle data of the synchronizing signal is inputted to the elimination circuit 10 of the synchronizing signal cycle data of a discontinuous horizontal synchronizing signal at the time of switching a channel. On the other hand, the horizontal synchronizing signal separated by the horizontal synchronizing separator circuit 2 is inputted to a continuity detection circuit 3 and the continuity of the horizontal synchronizing signal is monitored. When the continuity is detected, a control signal 16 is inputted to the circuit 10 eliminating the discontinuous cycle data of the horizontal synchronizing signal and the cycle data at the time of detecting the continuity before that is outputted when the discontinuity is detected. Thus the synchronizing signal with high stability can be generated.