Horizontal Synchronization Signal Input Compensation Device for Phase-Locked Loop

摘要

The present invention discloses a horizontal synchronous signal compensator of a phase locked loop (PLL) used in an on screen display circuit.;The horizontal synchronizing signal compensator of the phase synchronizing loop includes a synchronizing signal separator, a synchronizing signal detector, and a horizontal synchronizing signal compensator. The horizontal synchronizing signal compensator includes a one-shot pulse generator, a direct sync signal generator and a 10-bit counter of the window generator. It consists of a free run sync signal generator, a counter reset unit and a sync signal duty determiner.;Therefore, the horizontal synchronous signal compensator of the phase synchronous loop according to the present invention receives the horizontal synchronous signal input to the phase synchronous loop from (910-20) division of the 4FSC clock regardless of the synchronous signal detection output (SYD). By maintaining the divided clock time, it is possible to prevent the input voltage of the voltage controlled oscillator VCO of the phase locked loop PLL from shifting to one side. In addition, by uniformly and logically compensating the horizontal synchronizing signal inputted to the phase synchronizing loop PLL, the input voltage of the voltage controlled oscillator VCO of the phase synchronizing loop is made constant to perform stable locking operation of the phase synchronizing loop. It can be effective.