| 摘要 |
PURPOSE:To eliminate stably and surely the fluctuation of an input video signal by applying phase comparison between a signal subject to phase lock to horizontal synchronizing information included in a video signal with a reference signal and using the phase error to apply voltage control to the oscillating frequency of an oscillation circuit. CONSTITUTION:Synchronizing information is outputted separately at a synchronizing separation circuit 300 from an input video signal from a terminal 10. A horizontal synchronizing separation circuit 401 outputs separately the horizontal synchronizing information. An output (b) of a horizontal synchronizing separation circuit 401 is gated at an AND gate 405 by an output (e) of a latch circuit 400, its output triggers a monostable multivibrator circuit 406 to output a write start pulse with a prescribed time width. A phase locked loop circuit is constituted by a frequency division circuit 409, a phase comparator circuit 410, gate circuit 411, phase compensation circuit 412, oscillation circuit 407 and a frequency division circuit 413; and the oscillation output from the oscillation circuit 407 is phase-locked to a reference clock from a crystal oscillation circuit 408. |
