| 摘要 |
PURPOSE:To remove the various influences based on an abrupt phase lock by softly locking a phase control system by providing a reset pulse forming circuit. CONSTITUTION:When the pulse of a vertical synchronization pulse VD is varied due to channel switching or the like, a counter 2 is reset by the first reset pulse if the variation width falls within the pulse width of a window pulse, and the counter 2 is reset by the second, third reset pulses in response to the phase of the vertical synchronization pulse VD except the above case. Thus, an internal reference pulse Pca which is slower in variation of the phase that the pulse VD is supplied as the internal reference pulse in a phase control system 10, and a closed loop control is performed to lock the phase to the pulse Pca, with the result that the system 10 can be softly locked. |
