Liquid crystal display device having an improved precharge circuit and method of driving same

• US 20030132903A1
• Filed: 01/07/2003
• Published: 07/17/2003
• Est. Priority Date: 01/16/2002
• Status: Active Grant

• Current Assignee: Panasonic Intellectual Property Corporation of America (Panasonic Holdings Corporation)
• Original Assignee: Hitachi, Ltd.
• Inventors: Ueda, Shiro
• Granted Patent: US 6,980,190 B2
• Time in Patent Office: Days
• US Class Current: 345/87
• CPC Class Codes: G09G 2310/0248 Precharge or discharge of column electrodes before or after applying exact column voltages
• CPC Class Codes: G09G 2310/027 Details of drivers for data electrodes, the drivers handling digital grey scale data, e.g. use of D/A converters
• CPC Class Codes: G09G 2310/0297 Special arrangements with multiplexing or demultiplexing of display data in the drivers for data electrodes, in a pre-processing circuitry delivering display data to said drivers or in the matrix panel, e.g. multiplexing plural data signals to one D/A converter or demultiplexing the D/A converter output to multiple columns
• CPC Class Codes: G09G 2320/0223 Compensation for problems related to R-C delay and attenuation in electrodes of matrix panels, e.g. in gate electrodes or on-substrate video signal electrodes
• CPC Class Codes: G09G 3/3614 Control of polarity reversal in general
• CPC Class Codes: G09G 3/3659 the addressing of the pixel involving the control of two or more scan electrodes or two or more data electrodes, e.g. pixel voltage dependant on signal of two data electrodes
• CPC Class Codes: G09G 3/3688 suitable for active matrices only

Abstract

A liquid crystal display device includes a driver circuit for outputting a charging voltage at a beginning of a horizontal scanning period and then a gray scale voltage corresponding to a display data to a video signal line. The liquid crystal display device is driven by inverting a polarity of the gray scale voltage on a pixel electrode with respect to a common voltage on a common electrode every N lines of scanning lines, where N≧2 and by making a first charging time of the charging voltage corresponding to a first line of N lines of the scanning lines scanned immediately after inversion of the polarity of the gray scale voltage different from a second charging time of the charging voltage corresponding to a second line of the N lines scanned immediately succeeding the first line.

Claims

1. A method of driving a liquid crystal display device, said liquid crystal display device including

a liquid crystal layer,

a plurality of pixels arranged in a matrix configuration,

each of said plurality of pixels being provided with a pixel electrode for generating an electric field in said liquid crystal layer between said pixel electrode and a common electrode associated with said plurality of pixels in common,

a plurality of video signal lines coupled to said plurality of pixels,

a plurality of scanning lines arranged to intersect said plurality of video signal lines and coupled to said plurality of pixels, and

a driver circuit for outputting a charging voltage at a beginning of a horizontal scanning period and then a gray scale voltage corresponding to a display data to said plurality of video signal lines,

said method comprising:

inverting a polarity of said gray scale voltage with respect to a common voltage on said common electrode every N lines of said plurality of scanning lines, where N≧

2; and

making a first charging time of said charging voltage corresponding to a first line of N lines of said plurality of scanning lines scanned immediately after inversion of said polarity of said gray scale voltage different from a second charging time of said charging voltage corresponding to a second line of said N lines scanned immediately succeeding said first line.

2. A method of driving a liquid crystal display device according to claim 1, wherein said first charging time is longer than said second charging time.

3. A method of driving a liquid crystal display device according to claim 1, wherein said charging voltage is displaced toward a maximum gray scale voltage from a value of (said maximum gray scale voltage+a minimum gray scale voltage)/2,

where said maximum gray scale voltage is a greatest value in a range of said gray scale voltage of one polarity with respect to said common voltage, and said minimum gray scale voltage is a smallest value in said range of said gray scale voltage of said one polarity with respect to said common voltage.

4. A method of driving a liquid crystal display device according to claim 1, wherein said charging voltage is (a maximum gray scale voltage+a minimum gray scale voltage)/2,

where said maximum gray scale voltage is a greatest value in a range of said gray scale voltage of one polarity with respect to said common voltage, and said minimum gray scale voltage is a smallest value in said range of said gray scale voltage of said one polarity with respect to said common voltage.

5. A method of driving a liquid crystal display device according to claim 1, wherein said N is two.

6. A method of driving a liquid crystal display device, said liquid crystal display device including

a liquid crystal layer,

a plurality of pixels arranged in a matrix configuration,

each of said plurality of pixels being provided with a pixel electrode for generating an electric field in said liquid crystal layer between said pixel electrode and a common electrode associated with said plurality of pixels in common,

a plurality of video signal lines coupled to said plurality of pixels,

a plurality of scanning lines arranged to intersect said plurality of video signal lines and coupled to said plurality of pixels, and

a driver circuit for outputting a charging voltage at a beginning of a horizontal scanning period and then a gray scale voltage corresponding to a display data to said plurality of video signal lines,

said method comprising varying a charging time of said charging voltage with a distance from said driver circuit to a scanned one of said plurality of scanning lines.

7. A method of driving a liquid crystal display device according to claim 6, wherein said charging time increases with increasing distance from said driver circuit to a scanned one of said plurality of scanning lines.

8. A method of driving a liquid crystal display device according to claim 6, wherein

a polarity of said gray scale voltage with respect to a common voltage on said common electrode is inverted every N lines of said plurality of scanning lines, where N≧

2, and

a first one of said charging time of said charging voltage corresponding to a first line of N lines of said plurality of scanning lines scanned immediately after inversion of said polarity of said gray scale voltage is longer than a second one of said charging time of said charging voltage corresponding to a second line of said N lines scanned immediately succeeding said first line.

9. A method of driving a liquid crystal display device according to claim 8, wherein said N is two.

10. A method of driving a liquid crystal display device according to claim 6, wherein said charging voltage is displaced toward a maximum gray scale voltage from a value of (said maximum gray scale voltage+a minimum gray scale voltage)/2,

where said maximum gray scale voltage is a greatest value in a range of said gray scale voltage of one polarity with respect to said common voltage, and said minimum gray scale voltage is a smallest value in said range of said gray scale voltage of said one polarity with respect to said common voltage.

11. A method of driving a liquid crystal display device according to claim 6, wherein said charging voltage is (a maximum gray scale voltage+a minimum gray scale voltage)/2,

where said maximum gray scale voltage is a greatest value in a range of said gray scale voltage of one polarity with respect to said common voltage, and said minimum gray scale voltage is a smallest value in said range of said gray scale voltage of said one polarity with respect to said common voltage.

12. A method of driving a liquid crystal display device,

said liquid crystal display device including

a liquid crystal layer,

a plurality of pixels arranged in a matrix configuration,

each of said plurality of pixels being provided with a pixel electrode for generating an electric field in said liquid crystal layer between said pixel electrode and a common electrode associated with said plurality of pixels in common,

a plurality of video signal lines coupled to said plurality of pixels,

a plurality of scanning lines arranged to intersect said plurality of video signal lines and coupled to said plurality of pixels,

a driver circuit for outputting a charging voltage at a beginning of a horizontal scanning period and then a gray scale voltage corresponding to a display data to said plurality of video signal lines, and

a display control device for outputting an ac-driving signal for controlling ac-driving of said liquid crystal layer and for outputting a charge-control clock to said driver circuit,

said method comprising:

inverting a polarity of said gray scale voltage with respect to a common voltage on said common electrode every N lines of said plurality of scanning lines based upon said ac-driving signal, where N≧

2; and

varying a duration of a first level of said charge-control clock with time such that a first charging time of said charging voltage corresponding to a first line of N lines of said plurality of scanning lines scanned immediately after inversion of said polarity of said gray scale voltage is different from a second charging time of said charging voltage corresponding to a second line of said N lines scanned immediately succeeding said first line.

13. A method of driving a liquid crystal display device according to claim 12, wherein said duration of said first level of said charge-control clock corresponding to said first charging time is longer than said duration of said first level of said charge-control signal corresponding to said second charging time.

14. A method of driving a liquid crystal display device according to claim 12, wherein said charging voltage is displaced toward a maximum gray scale voltage from a value of (said maximum gray scale voltage+a minimum gray scale voltage)/2,

where said maximum gray scale voltage is a greatest value in a range of said gray scale voltage of one polarity with respect to said common voltage, and said minimum gray scale voltage is a smallest value in said range of said gray scale voltage of said one polarity with respect to said common voltage.

15. A method of driving a liquid crystal display device according to claim 12, wherein said charging voltage is (a maximum gray scale voltage+a minimum gray scale voltage)/2,

where said maximum gray scale voltage is a greatest value in a range of said gray scale voltage of one polarity with respect to said common voltage, and said minimum gray scale voltage is a smallest value in said range of said gray scale voltage of said one polarity with respect to said common voltage.

16. A method of driving a liquid crystal display device according to claim 12, wherein said N is two.

17. A method of driving a liquid crystal display device, said liquid crystal display device including

a liquid crystal layer,

a plurality of pixels arranged in a matrix configuration,

each of said plurality of pixels being provided with a pixel electrode for generating an electric field in said liquid crystal layer between said pixel electrode and a common electrode associated with said plurality of pixels in common,

a plurality of video signal lines coupled to said plurality of pixels,

a plurality of scanning lines arranged to intersect said plurality of video signal lines and coupled to said plurality of pixels,

a driver circuit for outputting a charging voltage at a beginning of a horizontal scanning period and then a gray scale voltage corresponding to a display data to said plurality of video signal lines, and

a display control device for outputting a charge-control clock to said driver circuit,

said method comprising varying a duration of a first level of said charge-control clock with time such that a charging time of said charging voltage varies with a distance from said driver circuit to a scanned one of said plurality of scanning lines.

18. A method of driving a liquid crystal display device according to claim 17, wherein said duration of said first level increases with increasing distance from said driver circuit to a scanned one of said plurality of scanning lines.

19. A method of driving a liquid crystal display device according to claim 17, wherein

said display control device outputs an ac-driving signal for controlling ac-driving of said liquid crystal layer to said driver circuit,

a polarity of said gray scale voltage with respect to a common voltage on said common electrode is inverted every N lines of said plurality of scanning lines based upon said ac-driving signal, where N≧

2, and

a first one of said charging time of said charging voltage corresponding to a first line of N lines of said plurality of scanning lines scanned immediately after inversion of said polarity of said gray scale voltage is longer than a second one of said charging time of said charging voltage corresponding to a second line of said N lines scanned immediately succeeding said first scanning line.

20. A method of driving a liquid crystal display device according to claim 19, wherein said N is two.

21. A method of driving a liquid crystal display device according to claim 17, wherein said charging voltage is displaced toward a maximum gray scale voltage from a value of (said maximum gray scale voltage+a minimum gray scale voltage)/2,

where said maximum gray scale voltage is a greatest value in a range of said gray scale voltage of one polarity with respect to said common voltage, and said minimum gray scale voltage is a smallest value in said range of said gray scale voltage of said one polarity with respect to said common voltage.

22. A method of driving a liquid crystal display device according to claim 17, wherein said charging voltage is (a maximum gray scale voltage+a minimum gray scale voltage)/2,

where said maximum gray scale voltage is a greatest value in a range of said gray scale voltage of one polarity with respect to said common voltage, and said minimum gray scale voltage is a smallest value in said range of said gray scale voltage of said one polarity with respect to said common voltage.

23. A liquid crystal display device comprising:

a liquid crystal layer;

a plurality of pixels arranged in a matrix configuration,

each of said plurality of pixels being provided with a pixel electrode for generating an electric field in said liquid crystal layer between said pixel electrode and a common electrode associated with said plurality of pixels in common;

a plurality of video signal lines coupled to said plurality of pixels;

a plurality of scanning lines arranged to intersect said plurality of video signal lines and coupled to said plurality of pixels;

a driver circuit for outputting a charging voltage at a beginning of a horizontal scanning period and then a gray scale voltage corresponding to a display data to said plurality of video signal lines; and

a display control device for outputting an ac-driving signal for controlling ac-driving of said liquid crystal layer and for outputting a charge-control clock to said driver circuit,

wherein

said display control device is provided with a pulse-duration-varying circuit for varying a duration of a first level of said charge-control clock, and

said driver circuit includes;

a polarity-inverting circuit for inverting a polarity of said gray scale voltage with respect to a common voltage on said common electrode every N lines of said plurality of scanning lines based upon said ac-driving signal, where N≧

2, and

a charging-time control circuit for controlling a charging time of said charging voltage based upon said duration of said first level of said charge-control clock such that a first charging time of said charging voltage corresponding to a first line of N lines of said plurality of scanning lines scanned immediately after inversion of said polarity of said gray scale voltage is different from a second charging time of said charging voltage corresponding to a second line of said N lines scanned immediately succeeding said first line.

24. A liquid crystal display device according to claim 23, wherein a duration of said first level of said charge-control clock corresponding to said first charging time is longer than that corresponding to said second charging time.

25. A liquid crystal display device according to claim 23, wherein said N is two.

26. A liquid crystal display device according to claim 23, wherein

said pulse-duration-varying circuit includes:

a maximum-clock-number setting circuit for setting a maximum number of externally supplied control clocks corresponding to a maximum of said duration of said first level of said charge-control clock;

a subtractor circuit for subtracting a number of externally supplied control clocks for a corresponding one of said plurality of scanning lines from said maximum number of externally supplied control clocks, and

a duration-setting circuit for setting said duration of said first level of said charge-control clock for said corresponding one of said plurality of scanning lines, based upon an output from said subtractor circuit.

27. A liquid crystal display device comprising:

a liquid crystal layer;

a plurality of pixels arranged in a matrix configuration,

each of said plurality of pixels being provided with a pixel electrode for generating an electric field in said liquid crystal layer between said pixel electrode and a common electrode associated with said plurality of pixels in common;

a plurality of video signal lines coupled to said plurality of pixels;

a plurality of scanning lines arranged to intersect said plurality of video signal lines and coupled to said plurality of pixels;

a driver circuit for outputting a charging voltage at a beginning of a horizontal scanning period and then a gray scale voltage corresponding to a display data to said plurality of video signal lines; and

a display control device for outputting a charge-control clock,

wherein

said display control device is provided with a pulse-duration-varying circuit for varying a duration of a first level of said charge-control clock, and

said driver circuit includes a charging-time control circuit for varying a charging time of said charging voltage based upon said duration of said first level of said charge-control clock such that said charging time of said charging voltage varies with a distance from said driver circuit to a scanned one of said plurality of scanning lines.

28. A liquid crystal display device according to claim 27, wherein said duration of said first level increases with increasing distance from said driver circuit to said scanned one of said plurality of scanning lines.

29. A liquid crystal display device according to claim 27, wherein

said display control device outputs an ac driving signal for controlling ac-driving of said liquid crystal layer to said driver circuit, and said driver circuit includes a polarity-inverting circuit for inverting a polarity of said gray scale voltage with respect to a common voltage on said common electrode every N lines of said plurality of scanning lines based upon said ac-driving signal, where N≧

2.

30. A liquid crystal display device according to claim 29, wherein said N is two.

31. A liquid crystal display device according to claim 27, wherein said pulse-duration-varying circuit includes:

a maximum-clock-number setting circuit for setting a maximum number of externally supplied control clocks corresponding to a maximum of said duration of said first level of said charge-control clock;

a subtractor circuit for subtracting a number of externally supplied control clocks for a corresponding one of said plurality of scanning lines from said maximum number of externally supplied control clocks, and

a duration-setting circuit for setting said duration of said first level of said charge-control clock for said corresponding one of said plurality of scanning lines, based upon an output from said subtractor circuit.