VIDEO SWITCHING DETECTING CIRCUIT - MATSUSHITA ELECTRIC IND CO LTD

Title:

VIDEO SWITCHING DETECTING CIRCUIT

Document Type and Number:

WIPO Patent Application WO/2001/093589

Kind Code:

A1

Abstract:

A video switching detecting circuit capable of detecting with a high precision using a construction of a smaller scale while suppressing the increase in the circuit scale. The video switching detecting circuit includes a PLL circuit having a phase comparator (1), an LPF (2), a VCO (3) and a frequency divider (4). The phase comparator (1) compares the phase of an external HD or an input signal pulse-shaped from a horizontal synchronizing signal with that of an internal HD or a reference signal frequency-divided from the output pulses of the VCO (3) in the PLL circuit. If the two signals have different phases, an error signal is outputted from the phase comparator (1). A first counter (6) counts and clocks the period, during which the error signal is active, that is, the time period during which a phase difference is generated. Moreover, a horizontal synchronization deciding unit (9) decides the locked state of the horizontal synchronization signal based on the duration of the phase difference continuation time period, and an output circuit (15) outputs a video switching detection signal when the out-of-phase is detected.

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Inventors:

SAKAI TAKEHIKO (JP)
KAWAI DAIJIRO (JP)
NAKAMURA KAZUHIDE (JP)

Application Number:

PCT/JP2001/004565

Publication Date:

December 06, 2001

Filing Date:

May 30, 2001

Export Citation:

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Assignee:

MATSUSHITA ELECTRIC IND CO LTD (JP)
SAKAI TAKEHIKO (JP)
KAWAI DAIJIRO (JP)
NAKAMURA KAZUHIDE (JP)

International Classes:

H04N5/268; G06F3/14; G09G5/12; H03L7/095; H04N7/18; (IPC1-7): H04N7/18; G09G5/00

Foreign References:

JPH10155145A	1998-06-09
JPH10301526A	1998-11-13
JPH1055161A	1998-02-24

Other References: