Title:
PLL CIRCUIT FOR DIGITAL DISPLAY DEVICE
Document Type and Number:
WIPO Patent Application WO/1998/007272
Kind Code:
A1
Abstract:
A PLL circuit is provided with a lock/unlock detecting circuit which detects the locked or unlocked state of the PLL circuit by comparing the phases of a horizontal synchronizing signal and a comparing signal with each other and an internal synchronizing signal generating circuit which outputs the comparing signal as an internal synchronizing signal when the locked state is detected or outputs the horizontal synchronizing signal as the internal synchronizing signal when the unlocked state is detected. Another mode of a PLL circuit is provided with a skew detecting circuit which resets a frequency dividing circuit upon detecting a skew which is deviated from a normal period in an external synchronizing signal, generates a dummy pulse upon detecting that no skew occurs in the external synchronizing signal in the normal period, and generates a reference signal in combination of the dummy pulse with the external synchronizing signal. When the skew detecting circuit detects a skew, the circuit also resets a phase comparator circuit. A digital display device having such a PLL circuit prevents distortion of the picture when the PLL circuit is in an unlocked state or a skew occurs.
Inventors:
NISHIMURA EIZO (JP)
KONDOU SATORU (JP)
KURITA MASANORI (JP)
KONDOU SATORU (JP)
KURITA MASANORI (JP)
Application Number:
PCT/JP1996/003395
Publication Date:
February 19, 1998
Filing Date:
November 20, 1996
Export Citation:
Assignee:
FUJITSU GENERAL LTD (JP)
NISHIMURA EIZO (JP)
KONDO SATORU (JP)
KURITA MASANORI (JP)
NISHIMURA EIZO (JP)
KONDO SATORU (JP)
KURITA MASANORI (JP)
International Classes:
G09G3/20; G09G5/00; H03L7/08; H03L7/095; H03L7/199; H04N5/12; H04N5/66; (IPC1-7): H04N5/12; H04N5/06; G09G3/20
Foreign References:
| JPS55115775A | 1980-09-05 | |||
| JPS61214868A | 1986-09-24 | |||
| JPH07170422A | 1995-07-04 | |||
| JPH05300470A | 1993-11-12 | |||
| JPH02288787A | 1990-11-28 | |||
| JPH05292432A | 1993-11-05 | |||
| JPH02109464A | 1990-04-23 |
Other References:
See also references of EP 0920194A4
Attorney, Agent or Firm:
Doi, Kenji (Doi & Associates Toshou-Building No. 3,
3-9-5, Shin-yokohama, Kohoku-k, Yokohama-shi Kanagawa 222, JP)
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