| 摘要 |
<p>PURPOSE:To stably obtain a signal accurately synchronized with a synchronizing signal by inhibiting the output of a synchronizing signal separating circuit from being supplied to a PLL circuit for a period wherein at least either of an equivalent pulse and a signal for damping prevention is generated. CONSTITUTION:A synchronizing signal separating circuit 11 compares an input video signal with a specific reference level and separates, detects, and supplies the equivalent pulse and signal for damping prevention to a vertical synchronizing signal separating circuit 12 to detect the vertical synchronizing signal in addition to a horizontal synchronizing signal and the vertical synchronizing signal, thereby outputting a signal with logic H while the vertical synchronizing signal is detected. A switch 18 is turned off when a pulse generating circuit 19 outputs the logic H and turned on when logic L is outputted. Consequently, the output of a monostable multivibrator 1 is inputted to a sample holding circuit 2 only for a period wherein the pulse generating circuit 19 outputs the logic L and not transmitted while the logic H is outputted.</p> |
