| 摘要 |
PURPOSE:To prevent a PLL from being pulled in again and to obtain a video signal free from disturbance by turning a phase difference between two signals inputted to a phase comparator to zero after the lapse of one period even when a video signal to be inputted is changed. CONSTITUTION:An inputted video signal is applied to a synchronous separator 2a to separate a horizontal synchronizing signal(SYN) from the current video signal, a video signal outputted from a delay part 1 is inputted to a synchronous separator 2b to extract a horizontal SYN from a video signal obtained one line before. A phase detecting part 3 detects a phase difference between the two horizontal SYNs outputted from the separators 2a, 2b and counts up the number of clocks in the phase difference. Then an adder 4 finds out an added result between the count result and a prescribed reference value and applies the added result to a time converter 5 to convert a time signal. Thereby even when the input of a video signal is switched, a time signal synchronized with the input video signal is always inputted to a phase comparator 6a in a PLL part 6 and the disturbance of an image due to the releading of the PLL part can be prevented. |
