DISPLAY DEVICE AND DRIVING METHOD THEREOF

• US 20130038621A1
• Filed: 08/07/2012
• Published: 02/14/2013
• Est. Priority Date: 08/08/2011
• Status: Active Grant

• Current Assignee: Samsung Display Company Limited (Samsung Electronics Co. Ltd.)
• Original Assignee: Samsung Display Company Limited (Samsung Electronics Co. Ltd.)
• Inventors: CHOI, Yong-Jun, JEONG, Jae-Won, CHOI, Jae-Suk, YEOM, Joo Seok, HAN, Young-Su, KIM, Myeong-Su, KIM, Yun-Jae, MOON, Seung Hwan, PARK, Jae Wan, BAEK, Seung-Ho, KIM, Jin-Soo, PARK, Po-Yun, OH, Kwan-Young, LEE, Min Joo, CHO, Jung Hwan
• Granted Patent: US 9,165,518 B2
• Time in Patent Office: Days
• US Class Current: 345/589
• CPC Class Codes: G06T 1/20 Processor architectures; Processor configuration, e.g. pipelining
• CPC Class Codes: G06T 1/60 Memory management
• CPC Class Codes: G09G 2300/04 Structural and physical details of display devices
• CPC Class Codes: G09G 2310/0237 Switching ON and OFF the backlight within one frame
• CPC Class Codes: G09G 2320/0247 Flicker reduction other than flicker reduction circuits used for single beam cathode-ray tubes
• CPC Class Codes: G09G 2320/0257 Reduction of after-image effects
• CPC Class Codes: G09G 2320/0626 for control of overall brightness
• CPC Class Codes: G09G 2320/064 by time modulation of the brightness of the illumination source
• CPC Class Codes: G09G 2320/103 Detection of image changes, e.g. determination of an index representative of the image change
• CPC Class Codes: G09G 2330/021 Power management, e.g. power saving
• CPC Class Codes: G09G 2340/0435 Change or adaptation of the frame rate of the video stream
• CPC Class Codes: G09G 2360/18 Use of a frame buffer in a display terminal, inclusive of the display panel
• CPC Class Codes: G09G 3/2092 Details of a display terminals using a flat panel, the details relating to the control arrangement of the display terminal and to the interfaces thereto suitable for both CRT and flat panel G09G5/003; specific for a CRT G09G1/165
• CPC Class Codes: G09G 3/3406 Control of illumination source illumination devices structurally associated with liquid crystal cells G02F1/1336
• CPC Class Codes: G09G 3/3648 using an active matrix G09G3/367 - G09G3/3696 take precedence
• CPC Class Codes: G09G 5/18 Timing circuits for raster scan displays specially adapted for television H04N ; synchronisation between the display unit and other display units, videodisc player G09G5/12

Abstract

The present invention provides a display device with reduced power consumption and that reduces changes in luminance, and perceptibility of flicker, and a driving method thereof. A display device according to an exemplary embodiment comprises: a display panel configured to display a still image and a motion picture; a signal controller configured to control signals for driving the display panel; and a graphics processing unit configured to transmit input image data to the signal controller, wherein the signal controller comprises a frame memory configured to store the input image data, and the display panel is driven at a first frequency when the motion picture is displayed and the display panel is driven at a second frequency that is lower than the first frequency when the still image is displayed.

Claims

1. A display device, comprising:

a display panel configured to display a still image and a motion picture;

a signal controller configured to control signals for driving the display panel; and

a graphics processing unit configured to transmit input image data to the signal controller,

wherein the signal controller comprises a frame memory configured to store the input image data, and

the display panel is driven at a first frequency when the motion picture is displayed and is driven at a second frequency that is lower than the first frequency when the still image is displayed.

2. The display device of claim 1, wherein

the graphics processing unit transmits a still image start signal and a still image end signal to the signal controller.

3. The display device of claim 2, wherein

the signal controller stores the input image data in the frame memory, outputs storage image data stored in the frame memory to the display panel at the second frequency, and inactivates the transmission of the input image data when the still image start signal is applied.

4. The display device of claim 3, wherein

the signal controller activates the transmission of the input image data and outputs the input image data to the display panel at the first frequency when the still image end signal is applied.

5. The display device of claim 2, wherein

a length of a vertical blank period when the display panel is driven at the second frequency is longer than a length of the vertical blank period when the display panel is driven at the first frequency.

6. The display device of claim 5, wherein

the display panel is driven at a frequency that is higher than the second frequency and lower than the first frequency for an S1 frame after the still image start signal is applied.

7. The display device of claim 6, wherein

the length of the vertical blank period is gradually increased for the S1 frame.

8. The display device of claim 5, wherein

the display panel is driven at a frequency that is higher than the second frequency and lower than the first frequency for an S2 frame after the still image end signal is applied.

9. The display device of claim 8, wherein

the length of the vertical blank period is gradually decreased for the S2 frame.

10. The display device of claim 2, wherein

the display panel comprises:

a substrate;

a gate line and a data line formed on the substrate;

a switching element connected to the gate line and the data line; and

a pixel electrode connected to the switching element, and

wherein the gate line is applied with a gate signal comprising a gate-on voltage and a gate-off voltage.

11. The display device of claim 10, wherein

a clock frequency of the gate signal when the display panel is driven at the second frequency is lower than a clock frequency of the gate signal when the display panel is driven at the first frequency.

12. The display device of claim 11, wherein

a length of a vertical blank period when the display panel is driven at the second frequency is longer than a length of the vertical blank period when the display panel is driven at the first frequency.

13. The display device of claim 2, wherein

the display panel is driven with the second frequency until a frame applied with the still image end signal is ended.

14. The display device of claim 13, wherein

the display panel comprises:

a gate line and a data line;

a gate driver configured to drive a gate line; and

a data driver configured to drive a data line, and

the signal controller transmits an STV signal and a CPV signal to the gate driver.

15. The display device of claim 14, wherein

the signal controller transmits the STV signal to the gate driver at a start position of one frame except for a position where the second frequency is changed into the first frequency.

16. The display device of claim 15, wherein

the signal controller is controlled for the widths of the CPV signal when the display panel is driven with the first frequency and the second frequency to be the same.

17. The display device of claim 16, wherein

the signal controller is controlled

for the width of the CPV signal to have the same width as a clock signal of p times when the display panel is driven with a first frequency, and

for the width of the CPV signal to have the same width as a clock signal of q times less than p times when the display panel is driven with the second frequency.

18. The display device of claim 15, wherein

the signal controller gamma-corrects the input image data when the display panel is driven with the second frequency and transmits the gamma-corrected image data to the display panel.

19. The display device of claim 2, wherein

the signal controller further comprises a frame counting unit configured to count the number of still image sequential frames inputted before the still image end signal is applied after the still image start signal is applied, and configured to count the number of motion picture sequential frames inputted until the still image start signal is applied after the still image end signal is applied.

20. The display device of claim 19, wherein

the signal controller stores the input image data in the frame memory and inactivates the transmission of the input image data when the number of the still image sequential frames is equal to or more than x, and activates the transmission of the input image data when the number of the motion picture sequential frames is equal to or more than y.

21. The display device of claim 20, wherein

the signal controller outputs the storage image data stored in the frame memory to the display panel at the second frequency when the number of the still image sequential frames is equal to or more than x, and outputs the input image data to the display panel at the first frequency when the number of the motion picture sequential frames is equal to or more than y.

22. The display device of claim 2, further comprising:

a light source unit configured to irradiate light to the display panel; and

a light source driver configured to control signals to drive the light source unit.

23. The display device of claim 22, wherein

the light source driver drives the light source unit at a first ratio when the display panel is driven at the first frequency, and drives the light source unit at a second ratio when the display panel is driven at the second frequency.

24. The display device of claim 23, wherein

the second ratio is lower than the first ratio when the display panel is a normally black mode, and

the second ratio is higher than the first ratio when the display panel is a normally white mode.

25. The display device of claim 24, wherein

the signal controller further comprises a signal receiving unit configured to transmit the input image data from the graphics processing unit, and a driving frequency selecting unit configured to select the first frequency when the still image is displayed and configured to select the second frequency when the motion picture is displayed.

26. The display device of claim 24, wherein

the light source driver comprises a driving frequency receiving unit configured to receive a driving frequency of the display panel from the signal controller, a light source unit driving ratio selecting unit configured to determine a driving ratio of the light source unit according to the driving frequency, and a light source driving signal generator configured to generate a signal for driving the light source according to the driving ratio of the light source unit.

27. The display device of claim 22, wherein

the light source driver constantly maintains a driving ratio of the light source unit when the display panel is driven with the first frequency, and periodically changes the driving ratio of the light source unit when the display panel is driven with the second frequency.

28. The display device of claim 27, wherein

the display panel is a normally black mode, and

the light source driver drives the light source unit with the first ratio when the display panel is driven with the first frequency, and drives the light source unit with the first ratio and a ratio that is sequentially decreased from the first ratio when the display panel is driven with the second frequency.

29. The display device of claim 28, wherein

the display panel comprises:

a gate line and a data line;

a gate driver configured to drive a gate line; and

a data driver configured to drive a data line, and

the signal controller transmits an STV signal to the gate driver at a start position of every frame.

30. The display device of claim 29, wherein

the light source driver drives the light source unit with the first ratio as a position where the STV signal is transmitted when the display panel is driven with the second frequency, and drives the light source unit with a ratio that is sequentially decreased from the first ratio before a next STV signal is transmitted.

31. The display device of claim 30, wherein

a transmission cycle of the STV signal when the display panel is driven with the first frequency is the same as a change cycle of a driving ratio of the light source unit when the display panel is driven with the second frequency.

32. The display device of claim 27, wherein

the display panel is a normally white mode, and

the light source driver drives the light source unit with the first ratio when the display panel is driven with the first frequency and drives the light source unit with the first ratio and a ratio that is sequentially increased from the first ratio when the display panel is driven with the second frequency.

33. The display device of claim 2, wherein

the display panel comprises:

a substrate;

a gate line, a data line, and a storage electrode line formed on the substrate;

a first switching element connected to the gate line and the data line; and

a storage capacitor connected to the first switching element and the storage electrode line,

wherein when the display panel is driven with the first frequency, a common voltage input to the storage electrode line has a constant value, and

when the display panel is driven with the second frequency, the common voltage has a value that is changed according to time.

34. The display device of claim 33, wherein

the display panel further comprises:

a second switching element and a third switching element formed between the storage electrode line and the storage capacitor; and

a storage electrode control line formed on the substrate,

wherein each of the second switching element and the third switching element comprises a control terminal, an input terminal, and an output terminal,

the input terminals of the second switching element and the third switching element are connected to the storage electrode line,

the output terminals of the second switching element and the third switching element are connected to the storage capacitor,

the control terminal of the second switching element is connected to the gate line, and

the control terminal of the third switching element is connected to the storage electrode control line.

35. The display device of claim 34, wherein

when the display panel is driven at the second frequency, the common voltage

has a first voltage at a first time and

has a second voltage that is higher than the first voltage at a second time.

36. The display device of claim 35, wherein

one frame comprises an effective period in which the image data is transmitted and a vertical blank period in which the image data is not transmitted,

the first period is the effective period, and

the second period is the vertical blank period.

37. The display device of claim 36, wherein

the control voltage input to the storage electrode control line has a gate-off voltage in the first period and has a gate-on voltage in the second period.

38. The display device of claim 35, wherein

when the display panel is driven with the second frequency,

the common voltage has a third voltage that is higher than the second voltage in the third period.

39. The display device of claim 38, wherein

one frame comprises an effective period in which the image data is transmitted and a vertical blank period in which the image data is not transmitted,

the first period is the effective period,

the second period is a portion of the vertical blank period, and

the third period is a remaining portion of the vertical blank period.

40. The display device of claim 33, wherein

when the display panel is driven with the second frequency, the common voltage has the first voltage in the first period and swings with the first voltage and the second voltage that is higher than the first voltage in the second period.

41. The display device of claim 40, wherein

the common voltage is gradually changed with a value between the first voltage and the second voltage when the first voltage is changed into the second voltage.

42. The display device of claim 2, further comprising:

a gate driver configured to drive the gate line; and

a data driver configured to drive the data line, and

the signal controller comprises

a calculator configured to calculate a representative value of storage image data stored in the frame memory,

a line memory configured to store the representative value, and

a kick-back corrector configured to generate auxiliary image data by correcting the representative value according to a kick-back voltage, and

the data driver applies an auxiliary voltage corresponding to the auxiliary image data to the data lines in a vertical blank range at the time of displaying the still image.

43. The display device of claim 42, wherein

the plurality of data lines are provided, and

the calculator calculates a representative value of the storage image data for each data line.

44. The display device of claim 43, wherein

the representative value is an average gray value of the storage image data.

45. The display device of claim 43, wherein

the representative value is an average gray value of upper t bits of the storage image data.

46. The display device of claim 43, wherein

the representative value is a middle value of a maximum gray value and a minimum gray value of the storage image data.

47. The display device of claim 43, wherein

the auxiliary image data is generated by

Ga=Gr−

dG (Ga;

a gray value of the auxiliary image data, Gr;

the representative value, dG;

a kick-back correction gray value depending on the representative value).

48. The display device of claim 47, wherein

the kick-back correction gray value is a value stored in a look-up table or calculated by a function.

49. The display device of claim 48, wherein

when the kick-back correction gray value is a value calculated by a function, and

the function

is generated by linear interpolation by using a kick-back correction gray value at a minimum gray, a kick-back correction gray value at a maximum gray, and a gray value when the magnitude of the kick-back correction gray value is a maximum.

50. The display device of claim 2, wherein

the display panel comprises:

gate lines and data lines;

a switching element of which a control terminal is connected to the gate line and an input terminal is connected to the data line; and

a pixel electrode connected to an output terminal of the switching element,

wherein a gate signal comprising gate-on voltage and gate-off voltage is applied to the gate line, and

the gate-off voltage when the display panel is driven at the second frequency has the following range;

Va−

0.2|Va|≦

Voff2≦

Va+0.2|Va|

(Voff2;

the gate-off voltage when the display panel is driven at the second frequency, Va;

voltage of the control terminal of the switching element when leakage current flowing between the input terminal and the output terminal of the switching element when the positive pixel voltage is applied to the pixel electrode and leakage current flowing between the input terminal and the output terminal of the switching element when the negative pixel voltage is applied to the pixel electrode are the same).

51. The display of claim 50, wherein

the gate-off voltage when the display panel is driven at the second frequency has the following range:

Va−

0.1|Va|≦

Voff2≦

Va+0.1|Va|

(Voff2;

the gate-off voltage when the display panel is driven at the second frequency, Va;

voltage of the control terminal of the switching element when leakage current flowing between the input terminal and the output terminal of the switching element when the positive pixel voltage is applied to the pixel electrode and leakage current flowing between the input terminal and the output terminal of the switching element when the negative pixel voltage is applied to the pixel electrode are the same).

52. The display device of claim 50, wherein

the gate-off voltage when the display panel is driven at the first frequency has the following range:

Va−

0.2|Va|≦

Voff1≦

Va+0.2|Va|

(Voff1;

the gate-off voltage when the display panel is driven at the first frequency, Va;

voltage of the control terminal of the switching element when leakage current flowing between the input terminal and the output terminal of the switching element when the positive pixel voltage is applied to the pixel electrode and leakage current flowing between the input terminal and the output terminal of the switching element when the negative pixel voltage is applied to the pixel electrode are the same).

53. The display device of claim 52, wherein

the gate-off voltage when the display panel is driven at the first frequency has the following range:

Va−

0.1|Va|≦

Voff1≦

Va+0.1|Va|

(Voff1;

the gate-off voltage when the display panel is driven at the first frequency, Va;

voltage of the control terminal of the switching element when leakage current flowing between the input terminal and the output terminal of the switching element when the positive pixel voltage is applied to the pixel electrode and leakage current flowing between the input terminal and the output terminal of the switching element when the negative pixel voltage is applied to the pixel electrode are the same).

54. The display device of claim 50, wherein

the gate-off voltage when the display panel is driven at the first frequency is the same as the gate-off voltage when the display panel is driven at the second frequency.

55. The display device of claim 50, wherein

the gate-off voltage when the display panel is driven at the first frequency is lower than the gate-off voltage when the display panel is driven at the second frequency.

56. The display device of claim 2, further comprising:

a gate driver configured to drive the gate line; and

a data driver configured to drive the data line,

wherein the signal controller

stores the input image data in the frame memory, applies storage image data stored in the frame memory to the data driver, and inactivates the transmission of the input image data, when the still image start signal is applied.

57. The display device of claim 56, wherein

the transmission of the input image data is activated and the input image data is applied to the data driver when the still image end signal is applied.

58. The display device of claim 56, wherein

the gate driver is attached at one side of the display panel.

59. The display device of claim 56, wherein

the gate driver is mounted in the display panel together with the gate line, the data line, and the switching element.

60. A method for driving a display device comprising a display panel displaying a moving picture and a still image, and a signal controller controlling signals to drive the display panel, comprising:

transmitting input image data and driving a display panel with a first frequency;

applying a still image start signal;

changing a driving frequency of the display panel into a second frequency that is lower than the first frequency;

applying a still image end signal; and

changing a driving frequency of the display panel into the first frequency.

61. The method of claim 60, wherein

the input image data is stored in the frame memory, the transmission of the input image data is inactivated, and storage image data stored in the frame memory is outputted to the display panel at the second frequency, when the still image start signal is applied.

62. The method of claim 61, wherein

the transmission of the input image data is activated and the input image data may be outputted to the display panel at the first frequency, when the still image end signal is applied.

63. The method of claim 60, wherein

a length of a vertical blank period when the display panel is driven at the second frequency is longer than a length of the vertical blank period when the display panel is driven at the first frequency.

64. The method of claim 63, wherein

the display panel is driven with a frequency that is higher than the second frequency and is lower than the first frequency during an S1 frame after the still image start signal is applied.

65. The method of claim 64, wherein

a length of the vertical blank period is gradually increased during the S1 frame.

66. The method of claim 63, wherein

the display panel is driven with a frequency that is higher than the second frequency and is lower than the first frequency during an S2 frame after the still image end signal is applied.

67. The method of claim 66, wherein:

a length of the vertical blank period is gradually decreased during the S2 frame.

68. The method of claim 60, wherein

the display panel comprises:

a substrate;

a gate line and a data line formed on the substrate;

a switching element connected to the gate line and the data line; and

a pixel electrode connected to the switching element,

wherein the gate line is applied with a gate signal comprising a gate-on voltage and a gate-off voltage.

69. The method of claim 68, wherein

a clock frequency of the gate signal when the display panel is driven at the second frequency is lower than the clock frequency of the gate signal when the display panel is driven at the first frequency.

70. The method of claim 69, wherein

a length of a vertical blank period when the display panel is driven at the second frequency is longer than a length of the vertical blank period when the display panel is driven at the first frequency.

71. The method of claim 60, wherein

the display panel is driven with the second frequency until the frame applied with the still image end signal ends, and

the driving frequency of the display panel is changed into the first frequency in a frame after the still image end signal is applied.

72. The method of claim 71, wherein

the display panel comprises:

a gate line and a data line;

a gate driver configured to drive the gate line; and

a data driver configured to drive the data line,

wherein the signal controller transmits an STV signal and a CPV signal to the gate driver.

73. The method of claim 72, wherein

the signal controller transmits the STV signal to the gate driver at the start position of every frame except for a position where the second frequency is changed into the first frequency.

74. The method of claim 73, wherein

the signal controller is controlled for the width of the CPV signal to be the same when the display panel is driven with the first frequency and the second frequency.

75. The method of claim 74, wherein

the signal controller is controlled for the width of the CPV signal to have the same width as the clock signal of p times when the display panel is driven with the first frequency, and for the width of the CPV signal to have the same width as the clock signal of q times less than p times when the display panel is driven with the second frequency.

76. The method of claim 73, wherein

the signal controller gamma-corrects image data when the display panel is driven with the second frequency, and transmits the gamma-corrected image data to the display panel.

77. The method of claim 60, further comprising:

counting the number of still image sequential frames inputted before the still image end signal is applied after the still image start signal is applied; and

counting the number of motion picture sequential frames inputted until the still image start signal is applied after the still image end signal is applied.

78. The method of claim 77, wherein

the signal controller stores the input image data in the frame memory and inactivates the transmission of the input image data when the number of the still image sequential frames is equal to or more than x, and activates the transmission of the input image data when the number of the motion picture sequential frames is equal to or more than y.

79. The method of claim 78, wherein

the signal controller outputs the storage image data stored in the frame memory to the display panel at the second frequency when the number of the still image sequential frames is equal to or more than x, and outputs the input image data to the display panel at the first frequency when the number of the motion picture sequential frames is equal to or more than y.

80. The method of claim 60, wherein

when the display panel is driven at the first frequency, the light source unit is driven at the first ratio, and when the display panel is driven at the second frequency, the light source unit is driven at the second ratio.

81. The method of claim 80, wherein

when the display panel is a normally black mode, the second ratio has a lower value than the first ratio, and

when the display panel is a normally white mode, the second ratio has a higher value than the first ratio.

82. The method of claim 80, wherein

the driving ratio of the light source unit according to the driving frequency of the display panel is selected by using a look-up table or a function.

83. The method of claim 80, wherein

the conversion of the driving frequency of the display panel and the driving ratio of the light source unit is performed in a vertical blank period.

84. The method of claim 60, wherein

when the display panel is driven with the first frequency, a driving ratio of the light source unit is constantly maintained, and

when the display panel is driven with the second frequency, the driving ratio of the light source unit is periodically changed.

85. The method of claim 84, wherein

the display panel is a normally black mode,

when the display panel is driven with the first frequency, the light source unit is driven with the first ratio, and

when the display panel is driven with the second frequency, the light source unit is driven with the first ratio and a ratio that is sequentially decreased from the first ratio.

86. The method of claim 85, wherein

the display panel comprises a gate line and a data line,

the display device further comprises

a gate driver configured to drive the gate line and

a data driver configured to drive the data line, and

the signal controller transmits an STV signal to the gate driver at the start position every frame.

87. The method of claim 86, wherein

when the display panel is driven with the second frequency,

the light source unit is driven with the first ratio at a position transmitting the STV signal, and

the light source unit is driven with a ratio that is sequentially decreased from the first ratio before transmission of a next STV signal.

88. The method of claim 87, wherein

a transmission cycle of the STV signal when the display panel is driven with the first frequency is the same as a change cycle of the driving ratio of the light source unit when the display panel is driven with the second frequency.

89. The method of claim 84, wherein

the display panel is a normally white mode,

when the display panel is driven with the first frequency, the light source unit is driven with the first ratio, and

when the display panel is driven with the second frequency, the light source unit is driven with the first ratio and a ratio that is sequentially increased from the first ratio.

90. The method of claim 60, wherein

when the display panel is driven with the first frequency,

the signal controller applies a common voltage having a constant value to the display panel, and

when the display panel is driven with the second frequency,

the signal controller applies a common voltage having a value that is changed to the display panel.

91. The method of claim 90, wherein

when the display panel is driven with the second frequency,

the signal controller

applies a common voltage having a first voltage in the first period and

a second voltage that is higher than the first voltage in the second period.

92. The method of claim 91, wherein

one frame comprises an effective period in which the image data is transmitted and a vertical blank period in which the image data is not transmitted,

the first period is the effective period, and

the second period is the vertical blank period.

93. The method of claim 91, wherein

when the display panel is driven with the second frequency,

the signal controller applies a common voltage having a third voltage that is higher than the second voltage in the third period to the display panel.

94. The method of claim 93, wherein

one frame comprises an effective period in which the image data is transmitted and a vertical blank period in which the image data is not transmitted,

the first period is the effective period,

the second period is a portion of the vertical blank period, and

the third period is a remaining portion of the vertical blank period.

95. The method of claim 90, wherein

when the display panel is driven with the second frequency,

the signal controller applies a common voltage having the first voltage in the first period and swinging between the first voltage and the second voltage that is higher than the first voltage in the second period.

96. The method of claim 95, wherein

the common voltage is gradually changed with a value between the first voltage and the second voltage when the first voltage is changed into the second voltage.

97. The method of claim 60, further comprising:

storing the input image data to the frame memory if the still image start signal is applied;

calculating a representative value of the storage image data stored to the frame memory;

correcting the representative value according to the kick-back voltage to generate and auxiliary image data; and

applying the auxiliary voltage corresponding to the auxiliary image data to the data line in the vertical blank period.

98. The method of claim 97, wherein:

the data line is provided in plural, and

the representative value of the storage image data is calculated for each data line.

99. The method of claim 98, wherein

the representative value is an average gray value of the storage image data.

100. The method of claim 98, wherein

the representative value is an average gray value of upper t bits of the storage image data.

101. The method of claim 98, wherein

the representative value is a middle value between a maximum gray value and a minimum gray value of the storage image data.

102. The method of claim 98, wherein

the auxiliary image data is generated by

Ga=Gr−

dG (Ga;

a gray value of the auxiliary image data, Gr;

the representative value, dG;

a kick-back correction gray value depending on the representative value).

103. The method of claim 102, wherein

the kick-back correction gray value is a value stored in a look-up table or calculated by a function.

104. The method of claim 103, wherein

when the kick-back correction gray value is a value calculated by the function,

the function

is generated by linear interpolation by using a kick-back correction gray value at a minimum gray, a kick-back correction gray value at a maximum gray, and a gray value when the magnitude of the kick-back correction gray value is a maximum.

105. The method of claim 60, wherein

when the display panel is driven at the second frequency,

the signal controller applies a gate-off voltage having a range

Va−

0.2|Va|≦

Voff2≦

Va+0.2|Va|

(Voff2;

the gate-off voltage when the display panel is driven at the second frequency, Va;

voltage of the control terminal of the switching element when leakage current flowing between the input terminal and the output terminal of the switching element when the positive pixel voltage is applied to the pixel electrode and leakage current flowing between the input terminal and the output terminal of the switching element when the negative pixel voltage is applied to the pixel electrode are the same)

to the display panel.

106. The method of claim 105, wherein

when the display panel is driven at the second frequency,

the signal controller applies a gate-off voltage having a range

Va−

0.1|Va|≦

Voff2≦

Va+0.1|Va|

(Voff2;

the gate-off voltage when the display panel is driven at the second frequency, Va;

voltage of the control terminal of the switching element when leakage current flowing between the input terminal and the output terminal of the switching element when the positive pixel voltage is applied to the pixel electrode and leakage current flowing between the input terminal and the output terminal of the switching element when the negative pixel voltage is applied to the pixel electrode are the same) to the display panel.

107. The method of claim 105, wherein

when the display panel is driven at the first frequency,

the signal controller applies a gate-off voltage having a range

Va−

0.2|Va|≦

Voff1≦

Va+0.2|Va|

(Voff1;

the gate-off voltage when the display panel is driven at the first frequency, Va;

voltage of the control terminal of the switching element when leakage current flowing between the input terminal and the output terminal of the switching element when the positive pixel voltage is applied to the pixel electrode and leakage current flowing between the input terminal and the output terminal of the switching element when the negative pixel voltage is applied to the pixel electrode are the same).

108. The method of claim 107, wherein

when the display panel is driven at the first frequency,

the signal controller applies a gate-off voltage having a range

Va−

0.1|Va|≦

Voff1≦

Va+0.1|Va|

(Voff1;

the gate-off voltage when the display panel is driven at the first frequency, Va;

voltage of the control terminal of the switching element when leakage current flowing between the input terminal and the output terminal of the switching element when the positive pixel voltage is applied to the pixel electrode and leakage current flowing between the input terminal and the output terminal of the switching element when the negative pixel voltage is applied to the pixel electrode are the same).

109. The method of claim 105, wherein

the gate-off voltage when the display panel is driven at the first frequency is the same as the gate-off voltage when the display panel is driven at the second frequency.

110. The method of claim 105, wherein

the gate-off voltage when the display panel is driven at the first frequency is lower than the gate-off voltage when the display panel is driven at the second frequency.