Liquid crystal display apparatus

• US 6,175,347 B1
• Filed: 05/21/1998
• Issued: 01/16/2001
• Est. Priority Date: 05/22/1997
• Status: Expired due to Term

• Current Assignee: Panasonic Intellectual Property Corporation of America (Panasonic Holdings Corporation)
• Original Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Inventors: Yui, Hirokatsu, Torii, Hiromitsu, Shindo, Yoshikuni
• Primary Examiner(s): Cuchlinski, Jr., William A.
• Assistant Examiner(s): Marc-Coleman, Marthe Y.
• Application Number:
  US09/081,812
• Time in Patent Office: 971 Days
• Field of Search: 345/3, 345/112, 345/113, 345/87
• US Class Current: 345/87
• CPC Class Codes: G09G 2340/0407 Resolution change, inclusive of the use of different resolutions for different screen areas
• CPC Class Codes: G09G 2340/0485 Centering horizontally or vertically
• CPC Class Codes: G09G 3/3611 Control of matrices with row and column drivers
• CPC Class Codes: G09G 5/005 Adapting incoming signals to the display format of the display terminal
• CPC Class Codes: G09G 5/006 Details of the interface to the display terminal specific for a display terminal using a CRT G09G1/167; using a flat panel G09G3/2096; circuits for interfacing with colour displays G09G5/04
• CPC Class Codes: G09G 5/008 Clock recovery

Abstract

A/D converters (15-17), a PLL circuit (18), a scan conversion circuit (1), counters (4 and 5), an OR circuit (3), flip-flops (7-13) for comparing a phase of an output signal from the OR circuit (3) with a phase of an enable signal, and a CPU (14) are provided in a LCD apparatus so that settings in the scan conversion circuit (1), counter (4 and 5), and PLL circuit (18) can be changed responsive to outputs from the flip-flops (10-13), whereby a location and a size of a picture displayed on the LCD as well as a sampling clock frequency used in the A/D conversion can be automatically adjusted.

Claims

1. A liquid crystal display apparatus for automatically adjusting a location and a size of a picture displayed on a liquid crystal display of said liquid crystal display apparatus comprising:

means for comparing a phase of an input video signal that has undergone a scan conversion with a phase of an enable signal indicating a display period of said liquid crystal display, and determining a comparing result; and

means for changing in accordance with said comparing result a conversion rate of said scan conversion and the phase of said enable signal.

2. The liquid crystal display apparatus of claim 1 further comprising:

an analog/digital converter for converting an input video signal from an analog form to a digital form;

a phase-locked loop circuit for producing a sampling clock used in said analog/digital converter;

a scan conversion circuit for converting a number of dots per horizontal period of the input video signal and a number of lines per vertical period of the input video signal;

a plurality of counters for generating an enable signal indicating a display period of said liquid crystal display;

a plurality of flip-flops for comparing a phase of digital video signal that has undergone a scan conversion at said scan conversion circuit and a phase of said enable signal; and

a central processing unit,

wherein said central processing unit changes responsive to an output from said plurality of flip-flops

     1) a conversion rate of said scan conversion circuit,

     2) a multiplication factor of said phase-locked loop circuit, and

     3) a counting condition of said plurality of counters to change a phase of said enable signal.

3. The liquid crystal display apparatus as defined in claim 2, wherein the phase of said digital video signal that has undergone a scan conversion and the phase of said enable signal are compared when said video signal that has undergone a scan conversion at said scan conversion circuit includes RGB signals in a digital form, said liquid crystal display apparatus further comprising an OR circuit for calculating OR of significant bits including the most significant bits of each of said RGB signals,

wherein said liquid crystal display apparatus compares the phase of an output signal from said OR circuit with the phase of said enable signal.

4. The liquid crystal display apparatus of claim 2, wherein the phase of said digital video signal that has undergone a scan conversion and the phase of said enable signal are compared when said video signal that has undergone a scan conversion at said scan conversion circuit includes RGB signals in a digital form, said liquid crystal display apparatus further comprising:

an OR circuit for calculating OR of significant bit of each of said RGB signals,

wherein said liquid crystal display apparatus compares the phase of an output signal from said OR circuit with the phase of said enable signal.

5. The liquid crystal display apparatus as defined in claim 1, further comprising:

a scan conversion circuit for converting a number of dots per horizontal period of the input video signal and a number of lines per vertical period of the input video signal; and

an enable signal generation circuit for generating an enable signal indicating a display period of said liquid crystal display.

6. The liquid crystal display apparatus as defined in claim 5,

wherein said enable signal generation circuit comprises a plurality of counters and an AND circuit, said enable signal generation means generates an enable signal indicating a display period of said liquid crystal display;

and

said means for comparing comprises a plurality of flip-flops, said means for comparing compares of phase of a video signal that has undergone a scan conversion with a phase of said enable signal.

7. The liquid crystal display apparatus as defined in claim 5, further comprising:

an analog/digital converter for converting an input video signal from an analog form to a digital form;

a phase-locked loop circuit for generating a sampling clock used in said analog/digital converter; and

a central processing unit,

wherein said central processing unit changes responsive to an output from said plurality of flip-flops

     1) a conversion rate of said scan conversion circuit,

     2) a multiplication factor of said phase-locked loop circuit, and

     3) a counting condition of said plurality of counters in order to change a phase of said enable signal.

8. The liquid crystal display apparatus as defined in claim 5,

wherein a phase of a digital video signal that has undergone a scan conversion and a phase of said enable signal are compared when said video signal that has undergone a scan conversion at said scan conversion circuit includes RGB signals in a digital form.

said liquid crystal display apparatus further comprising:

an OR circuit for calculating OR of significant bits including the most significant bits of each of said RGB signals,

wherein said liquid crystal display apparatus compares a phase of an output signal from said OR circuit with the phase of said enable signal.

9. The liquid crystal display apparatus as defined in claim 5,

wherein a phase of digital video signal that has undergone a scan conversion and a phase of said enable signal are compared when said video signal that has undergone a scan conversion at said scan conversion circuit includes RGB signals in a digital form,

said liquid crystal display apparatus further comprising:

an OR circuit for calculating OR of the most significant bits of each of said RGB signals,

wherein said liquid crystal display apparatus compares the phase of an output signal from said OR circuit with the phase of said enable signal.

10. A liquid crystal display apparatus comprising:

means for comparing a phase of digital RGB signals with a phase of an enable signal indicative of a display period of a liquid crystal display; and

means for adjusting a sampling clock frequency responsive to a result output from said means for comparing such that said sampling clock frequency which is used in an analog/digital conversion from analog RGB signals to digital RGB signals coincides with a dot clock frequency that produced said analog RGB signals.

11. The liquid crystal display apparatus of claim 10 further comprising:

an analog/digital converter for converting analog RGB signals produced in a signal source to digital RGB signals;

a phase-locked loop circuit for producing a sampling clock of said analog/digital converter;

a plurality of counters for producing an enable signal indicative of a display period of said liquid crystal display;

an OR circuit for finding OR of the most significant bit of each of said digital RGB signals;

a plurality of flip-flops for comparing phases of an output signal from said OR circuit with a phase of said enable signal; and

a central processing unit for changing, in response to an output from said plurality of flip-flops, a multiplication factor of said phase locked loop circuit.

12. A liquid crystal display apparatus for automatically adjusting a location and a size of a picture displayed on a liquid crystal display of said liquid crystal display apparatus comprising:

an analog/digital converter for converting input analog RGB signals to digital RGB signals;

a phase-locked loop circuit for generating a sampling clock signal for supplying to said analog/digital converter;

an OR circuit for calculating OR of the most significant bits of each of said digital RGB signals;

means for comparing a phase of an output signal from said OR circuit with a phase of an enable signal indicating a display period of said liquid crystal display; and

means for adjusting a sampling clock signal frequency output from said phase-locked loop circuit responsive to an output signal from said means for comparing so that the frequency and phase of the sampling clock signal which is used in said analog/digital conversion circuit coincides with a frequency and phase of a dot clock that produced said analog RGB signals.

13. The liquid crystal display apparatus as defined in claim 12, wherein said means for comparing comprises a plurality of flip-flops,

said liquid crystal display apparatus further comprising:

a plurality of counters for generating an enable signal indicating a display period of said liquid crystal display; and

a central processing unit for changing a multiplication factor of said phase-locked loop circuit responsive to an output from said plurality of flip-flops.

14. A method for automatically adjusting a location and a size of a picture displayed on a liquid crystal display of a liquid crystal display apparatus comprising:

performing a scan conversion for an input video signal at a predetermined conversion rate;

comparing a phase of said video signal that has undergone a scan conversion with a phase of an enable signal indicating a display period of said liquid crystal display; and

controlling a conversion rate of said scan conversion, a multiplication factor of a phase-locked loop circuit, and a phase of said enable signal responsive to a result of said step of comparing.

15. The method for automatically adjusting a location and a size of a picture displayed on a liquid crystal display of a liquid crystal display apparatus as defined in claim 14, further comprising:

converting an input video signal from an analog form to a digital form;

converting a number of dots per horizontal period of the input video signal that has undergone an analog/digital conversion and a number of lines per vertical period of the input video signal at a predetermined conversion rate;

generating an enable signal indicating a display period of said liquid crystal display using a plurality of counters, an AND circuit, and a central processing unit; and

comparing a phase of said converted input video signal and a phase of said enable signal using a plurality of flip-flops.

16. The method for automatically adjusting a location and a size of a picture displayed on a liquid crystal display of a liquid crystal display apparatus as defined in claim 14, further comprising:

calculating OR of significant bits including the most significant bits of each of said RGB signals when digital video signal converted by said scan conversion circuit includes RGB signals; and

comparing a phase of OR output signal in the step of calculating OR with a phase of said enable signal.

17. The method for automatically adjusting a location and a size of a picture displayed on a liquid crystal display of a liquid crystal display apparatus as defined in claim 14, further comprising:

changing responsive to an output from said plurality of flip-flops

     1) a conversion rate of said scan conversion circuit,

     2) a multiplication factor or said phase-locked loop circuit, and

     3) a counting condition of said plurality of counters in order to change a phase of said enable signal.