Synchronizing signal separating circuit with controlled flywheel stage

Abstract

A synchronizing signal separating circuit for a television receiver, comprising: a source of a video signal having a line synchronizing signal component; a line synchronizing signal component separator having an amplitude selective stage and having a flywheel stage imparting a response time constant to the separator which enhances noise immunity; a delay circuit for the video signal, for example a multiple line delay, coupled ,between the video signal source and the separator; a control circuit coupled to the video signal source and evaluating the time positions of line synchronizing pulses of a plurality of successive lines to identify a kind of line phase disturbance in which the line phase of an entire raster is displaced, the control circuit supplying a control signal to the separator indicative of the kind of phase disturbance; and, the flywheel stage being temporarily rendered inoperative responsive to the control signal, for example by temporarily decreasing the response time of the separator, upon identification of the kind of line phase disturbance in which the line phase of an entire raster is displaced. The control circuit may comprise: a second line synchronizing signal component separator; a phase comparator; a digital memory for phase deviations determined by the phase comparator; and, a counter for phase deviatons which generates the control signal upon reaching a predetermined number of phase deviations.