| 摘要 |
PURPOSE:To attain rapid tracing to phase discontinuity by stopping phase comparison just after the occurrence of phase discontinuous consecutive point of a horizontal synchronizing signal, resetting a counter after the end of the counting of a VCO output so as to count the VCO output. CONSTITUTION:Phase comparison stop circuits 21, 25 detects phase discontinuous point in the horizontal synchronizing signal and stops the phase comparison just after the occurrence of phase discontinuous point. A time t1 till the count of the counter is finished is stored from the H pulse by a reset circuit comprising a counter (2)16, a latch circuit 17, a comparator 19 and gate circuits 20, 26, the counter 24 is reset at a point of time after the time t1 from the H pulse P1 just after the head switching and no sampling is applied to the pulse P1. Thus, the effect of discontinuity by the head switching is minimized to enhance the tracking performance. |
