LINE SYNCHRONIZING CIRCUIT WITH FINE/COARSE CONTROL

摘要

A line synchronizing circuit for a picture display device comprising a control loop for controlling a line oscillator. An incoming line synchronizing signal and also a reference signal generated by the oscillator are applied to a phase discriminator circuit. The output signal of the phase discriminator circuit is smoothed to obtain the control voltage for the oscillator. Pull-in of the control loop is established by means of a coincidence detector. Prior to that, an edge of the reference signal is compared with the center instant of a line synchronizing pulse. When the control loop is in the pulled-in state, it is changed by the coincidence detector to compare the leading edge of a line synchronizing pulse to the center instant between the said edge of the reference signal and its first preceding edge.