Liquid crystal display device

• US 6,756,958 B2
• Filed: 08/17/2001
• Issued: 06/29/2004
• Est. Priority Date: 11/30/2000
• Status: Expired due to Term

• Current Assignee: Panasonic Liquid Crystal Display Company Limited (Panasonic Holdings Corporation)
• Original Assignee: Hitachi, Ltd.
• Inventors: Kitajima, Masaaki, Suzuki, Masahiko, Furuhashi, Tsutomu, Kawabe, Kazuyoshi, Ooishi, Yoshihisa
• Primary Examiner(s): Chang, Kent
• Assistant Examiner(s): SHENG, TOM V
• Application Number:
  US09/931,213
• Publication Number:
  US 20020063703A1
• Time in Patent Office: 1,047 Days
• Field of Search: 345/52, 345/89, 345/92, 345/95, 345/211-213
• US Class Current: 345/95
• CPC Class Codes: G09G 2320/0233 Improving the luminance or brightness uniformity across the screen
• CPC Class Codes: G09G 3/3648 using an active matrix G09G3/367 - G09G3/3696 take precedence
• CPC Class Codes: G09G 3/3655 Details of drivers for counter electrodes, e.g. common electrodes for pixel capacitors or supplementary storage capacitors
• CPC Class Codes: G09G 3/3677 suitable for active matrices only
• CPC Class Codes: G09G 3/3696 Generation of voltages supplied to electrode drivers

Abstract

In a liquid crystal display device including a liquid crystal panel for displaying a tone in correspondence with a potential difference between a drain voltage and a common voltage, a drain driver circuit for generating the drain voltage corresponding to display data and applying the drain voltage to the liquid crystal panel, and a gate driver circuit for selecting a scanning line in the liquid crystal panel to which the drain voltage is applied, a power-supply circuit executes a comparative calculation of a reference common voltage and a feedback common voltage, then applying, to the liquid crystal panel, the common voltage obtained as a result of the comparative calculation, the reference common voltage whose potential level having been adjusted, the feedback common voltage is fedback from the liquid crystal panel.

Claims

1. A display device, comprising:

a display panel for displaying a tone in correspondence with a potential difference between a drain voltage and a common voltage which are applied to a plurality of switching elements,

a drain driver circuit for generating said drain voltage corresponding to said display data and applying said drain voltage to said display panel,

a gate driver circuit for selecting a scanning line in said display panel to which said drain voltage is applied, and

a power-supply circuit for executing a comparative calculation of a reference common voltage and a feedback common voltage so as to apply said common voltage to said display panel, said reference common voltage having an adjustable potential level, said feedback common voltage being fedback from said display panel, and said common voltage being obtained as a result of said comparative calculation,

wherein, if said drain voltage is in phase with said common voltage, a gate-off voltage applied at a section of pixels of said display panel is in phase with said drain voltage and said common voltage at the section of pixels of said display panel, and, if said drain voltage is in opposite phase to said common voltage, said gate-off voltage applied at the section of pixels of said display panel has an intermediate potential between said drain voltage and said common voltage at the section of pixels of said display.

2. The display device as claimed in claim 1, wherein, when said reference common voltage transitions to a higher potential, said common voltage applied to said display panel transitions to an even higher potential than said reference common voltage.

3. The display device as claimed in claim 1, wherein, when said reference common voltage transitions to a lower potential, said common voltage applied to said display panel transitions to an even lower potential than said reference common voltage.

4. The display device as claimed in claim 1, wherein said power-supply circuit alternates a gate-off voltage in the same phase as that of said reference common voltage, and applies said gate-off voltage to said gate driver circuit, said gate-off voltage being used for switching off gates of said switching elements in said display panel.

5. The display device as claimed in claim 1, wherein said power-supply circuit converts a gate-off voltage into a high-impedance state, and applies said gate-off voltage to said gate driver circuit, said gate-off voltage being used for switching off gates of said switching elements in said display panel.

6. The display device as claimed in claim 1, wherein said power-supply circuit generates a gate-off voltage, and applies said gate-off voltage to said gate driver circuit, said gate-off voltage being used for switching off gates of said switching elements in said display panel,

an amplitude quantity of said gate-off voltage in a case where said potential difference between said drain voltage and said common voltage is small is larger in comparison with an amplitude quantity of said gate-off voltage than a potential difference is between said drain voltage and said common voltage in a case where said potential difference between said drain voltage and said common voltage is large.

7. The display device as claimed in claim 1, wherein said power-supply circuit comprises a calculating circuit for adjusting said potential level of said reference common voltage, an amplifying circuit for executing said comparative calculation of said reference common voltage and said feedback common voltage, and current amplifying circuit for amplifying current of said comparatively-calculated common voltage.

8. The display device as claimed in claim 1, wherein said feedback common voltage is fedback to said power-supply circuit from at least one of an upper-portion side and a central-portion side of said display panel.

9. The display device as claimed in claim 1, wherein said power-supply circuit alternates said reference common voltage on each said scanning line basis.

10. The display device as claimed in claim 1,

wherein an amplitude of said gate-off voltage at the section of pixels of said display panel in a case where said drain voltage is in phase with said common voltage is larger than the amplitude of said gate-off voltage at said section of pixels in a case where said drain voltage is in opposite phase to said common voltage.

11. The display device as claimed in claim 1, wherein said intermediate potential of said gate-off voltage is a substantially fixed potential level.

12. A display device, comprising:

a display panel,

a drain driver circuit for generating a drain voltage corresponding to display data and applying said drain voltage to said display panel,

a gate driver circuit for selecting a scanning line in said display panel to which said drain voltage is applied, and

a power-supply circuit for generating a common voltage in response to at least one of a load constant of said display panel and a common voltage distortion caused by said display data, and applying said common voltage to said display panel, said common voltage becoming a reference of said drain voltage,

wherein, if said drain voltage is in phase with said common voltage, a gate-off voltage applied at a section of pixels of said display panel is in phase with said drain voltage and said common voltage at the section of pixels of said display panel, and, if said drain voltage is in opposite phase to said common voltage, said gate-off voltage applied at the section of pixels of said display panel has an intermediate potential between said drain voltage and said common voltage at the section of pixels of said display panel.

13. The display device as claimed in claim 12, wherein said intermediate potential of said gate-off voltage is a substantially fixed potential level.

14. A method of driving a display device, comprising the steps of:

inputting, into a display panel, a drain voltage corresponding to display data,

inputting a common voltage from a power-supply circuit into said display panel, said common voltage becoming a reference of said drain voltage, and

feedbacking, to said power-supply circuit, said common voltage outputted from said display panel,

wherein, if said drain voltage is in phase with said common voltage, a gate-off voltage applied at a section of pixels of said display panel is in phase with said drain voltage and said common voltage at the section of pixels of said display panel, and, if said drain voltage is in opposite phase to said common voltage, said gate-off voltage applied at the section of pixels of said display panel has an intermediate potential between said drain voltage and said common voltage at the section of pixels of said display panel.

15. The method of driving a display device as claimed in claim 14, wherein said intermediate potential of said gate-off voltage is a substantially fixed potential level.

16. A display device, comprising:

a display panel,

a drain driver circuit for generating a drain voltage corresponding to display data and applying said drain voltage to said display panel,

a gate driver circuit for selecting a scanning line in said display panel to which said drain voltage is applied, and

a power-supply circuit for converting a gate-off voltage into a high-impedance state and applying said gate-off voltage to said gate driver circuit, said gate-off voltage being used for switching off gates of switching elements in said display panel,

wherein, if said drain voltage is in phase with said common voltage, a gate-off voltage applied at a section of pixels of said display panel is in phase with said drain voltage and said common voltage at the section of pixels of said display panel, and, if said drain voltage is in opposite phase to said common voltage, said gate-off voltage applied at the section of pixels of said display panel has an intermediate potential between said drain voltage and said common voltage at the section of pixels of said display panel.

17. The display device as claimed in claim 16, wherein an amplitude of said gate-off voltage at the section of pixels of said display panel in a case where said drain voltage is in phase with said common voltage is larger than the amplitude of said gate-off voltage at said section of pixels in a case where said drain voltage is in opposite phase to said common voltage.

18. The display device as claimed in claim 16, wherein said intermediate potential of said gate-off voltage is a substantially fixed potential level.

19. A display device, comprising:

a display panel,

a drain driver circuit for generating a drain voltage corresponding to display data and applying said drain voltage to said display panel,

a gate driver circuit for selecting a scanning line in said display panel to which said drain voltage is applied, and

a power-supply circuit for voltage-dividing a gate-off voltage at a higher potential and a gate-off voltage at a lower potential, and applying voltage-divided gate-off voltages to said gate driver circuit,

wherein, if said drain voltage is in phase with said common voltage, a gate-off voltage applied at a section of pixels of said display panel is in phase with said drain voltage and said common voltage at the section of pixels of said display panel, and, if said drain voltage is in opposite phase to said common voltage, said gate-off voltage applied at the section of pixels of said display panel has an intermediate potential between said drain voltage and said common voltage at the section of pixels of said display panel.

20. The display device as claimed in claim 19, wherein said intermediate potential of said gate-off voltage is a substantially fixed potential level.

21. A display device comprising:

a display panel for displaying a tone in correspondence with a potential difference between a drain voltage and a common voltage which are applied to a plurality of switching elements,

a drain driver circuit for generating said drain voltage corresponding to said display data and applying said drain voltage to said display panel,

a gate driver circuit for selecting a scanning line in said display panel to which said drain voltage is applied, and

means for suppressing transverse smear in said display device, including means for improving convergence of at least one of said common voltage and said drain voltage inside said display panel, including

a power-supply circuit for executing a comparative calculation of a reference common voltage and a feedback common voltage so as to apply said common voltage to said display panel, said reference common voltage having an adjustable potential level, said feedback common voltage being fedback from said display panel, and said common voltage being obtained as a result of said comparative calculation,

wherein, if said drain voltage is in phase with said common voltage, a gate-off voltage applied at a section of pixels of said display panel is in phase with said drain voltage and said common voltage at the section of pixels of said display panel, and, if said drain voltage is in opposite phase to said common voltage, said gate-off voltage applied at the section of pixels of said display panel has an intermediate potential between said drain voltage and said common voltage at the section of pixels of said display panel.