Horizontal sync signal regeneration circuit

Abstract

Abstract PURPOSE:To remove distortion in display picture by using a phase controlled oscillator in separating a horizontal synchronizing signal from a composite synchronizing signal, making said oscillation oscillate autonomously at the ending time of one frame of scanning, and thereby generating the horizontal synchronizing signal having a continuity with a horizontal scanning period. CONSTITUTION:From a synchronizing signal separating circuit 1, the composite synchronizing signal is inputted to a J-KFF 3 through an inverter 4. The J-KFF 7 outputs an ending signal and turns on a gate 10. A PLL is formed with a phase comparator 9, a voltage controlled oscillator 12, and a frequency divider 13. The oscillator 12 outputs a pulse signal that has the same timing as that of the Q1-terminal-output of the FF 3 i.e. an ending-timing corresponding with the leading edge of a horizontal synchronizing signal, and outputs said signal to a terminal 14 as a horizontal synchronizing signal. When the FF 3 is reset during a period when vertical synchronizing signals are being outputted and after the last horizontal synchronizing signal in a frame is inputted, an FF 7 outputs a high-level signal to turn off the gate 10, when the oscillator 12 operates autonomously based on the voltage of a voltage holding circuit 11, so that the oscillation is continued with a period approximately coinciding with that of a horizontal synchronizing signal.

Inventors

• 👤 Yoshiji Kimura
• 👤 佳司 木村

Bibliographic Details