JPH0377558U

JPH0377558U -

Info

Publication number: JPH0377558U
Application number: JP13731889U
Authority: JP
Priority date: 1989-11-29
Filing date: 1989-11-29
Publication date: 1991-08-05

Description

[Brief explanation of drawings]

第１図は本考案の一実施例による同期信号検出
回路の構成を示すブロツク図、第２図は従来のテ
レビジヨン受像機全体の回路構成を示すブロツク
図、第３図は第２図における同期信号検出回路の
詳細を示すブロツク図、第４図ａ〜ｃは従来の同
期信号検出回路を用いた場合の画像表示状態を示
す図である。１２……チユーナ、１３……中間周波増幅回路
、１４……映像検波回路、１５……クロマ信号処
理回路、１６……表示駆動回路、１７……表示部
、１８……同期信号検出回路、１９……制御部、
２３……キー入力部、３１……同期信号分離回路
、３２……位相比較回路、３３ａ……第１ループ
フイルタ、３３ｂ……第２ループフイルタ、３４
……電圧制御発振器、３５……モード切換スイツ
チ。 FIG. 1 is a block diagram showing the configuration of a synchronization signal detection circuit according to an embodiment of the present invention, FIG. 2 is a block diagram showing the entire circuit configuration of a conventional television receiver, and FIG. 3 is a synchronization signal detection circuit in FIG. FIGS. 4a to 4c are block diagrams showing details of the signal detection circuit, and are diagrams showing image display states when a conventional synchronization signal detection circuit is used. 12... Tuner, 13... Intermediate frequency amplification circuit, 14... Video detection circuit, 15... Chroma signal processing circuit, 16... Display drive circuit, 17... Display unit, 18... Synchronization signal detection circuit, 19 ...control section,
23...Key input unit, 31...Synchronizing signal separation circuit, 32...Phase comparison circuit, 33a...First loop filter, 33b...Second loop filter, 34
...Voltage controlled oscillator, 35...Mode changeover switch.

Claims

[Claims for Utility Model Registration] (1) A synchronization signal separation circuit that separates a horizontal synchronization signal in a video signal, a voltage controlled oscillator that generates a horizontal pulse signal, and a horizontal synchronization signal separated by the synchronization signal separation circuit. and a phase comparison circuit that detects a phase difference by comparing the horizontal pulse signals outputted from the voltage controlled oscillator, and first and second loop filters each having a different time constant to which the output signal of the phase comparison circuit is input. and switching means for switching the output signals of the first and second loop filters between a television reception mode and a video input mode, and inputting the output signals to the voltage controlled oscillator as an oscillation control signal. Synchronous signal detection circuit. (2) A sync signal separation circuit that separates a horizontal sync signal in a video signal, a voltage controlled oscillator that generates a horizontal pulse signal, and a horizontal sync signal separated by the sync signal separation circuit and output from the voltage controlled oscillator. a phase comparator circuit for detecting a phase difference by comparing horizontal pulse signals, and a phase comparator circuit provided between the output terminal of the phase comparator circuit and the input terminal of the voltage controlled oscillator;
A synchronizing signal detection circuit comprising: a loop filter from which different types of time constants can be selected; and switching means for switching the time constant of the loop filter between a television reception mode and a video input mode.