Liquid crystal display and a driving method thereof

• US 20030098839A1
• Filed: 08/19/2002
• Published: 05/29/2003
• Est. Priority Date: 11/26/2001
• Status: Active Grant

• Current Assignee: Samsung Display Company Limited (Samsung Electronics Co. Ltd.)
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: Lee, Baek-Woon
• Granted Patent: US 7,095,393 B2
• Time in Patent Office: Days
• US Class Current: 345/89
• CPC Class Codes: G09G 2320/0252 Improving the response speed
• CPC Class Codes: G09G 2320/0261 in the context of movement of objects on the screen or movement of the observer relative to the screen
• CPC Class Codes: G09G 2320/0285 using tables for spatial correction of display data
• CPC Class Codes: G09G 2320/041 Temperature compensation
• CPC Class Codes: G09G 2320/06 Adjustment of display parameters
• CPC Class Codes: G09G 2320/10 Special adaptations of display systems for operation with variable images
• CPC Class Codes: G09G 2340/16 Determination of a pixel data signal depending on the signal applied in the previous frame
• CPC Class Codes: G09G 3/2011 by amplitude modulation
• CPC Class Codes: G09G 3/3648 using an active matrix G09G3/367 - G09G3/3696 take precedence

Abstract

Disclosed is an LCD and driving method thereof. The LCD according to the present invention generates modification image signals by considering image signals of present and previous frames, and then supplies data voltages corresponding to the generated modification image signals to the data lines. At this time, the value for modifying the present frame image signal varies according to a modification parameter that is at least one among a temperature, an image quality selected by a user, and an environment of the LCD.

Claims

1. A liquid crystal display (LCD), comprising:

an LCD panel comprising a plurality of gate lines for transmitting scanning signals, a plurality of data lines that are insulated from and that cross the gate lines for transmitting image signals, and a plurality of pixels that are formed in an area surrounded by the gate lines and the data lines and that are arranged as a matrix pattern and that have switching elements connected to the gate lines and data lines;

a data gray signal modifier for receiving gray signals from a data gray signal source, and for outputting modification gray signals by considering gray signals of present and previous frames according to one or more modification parameters;

a gate driver for sequentially supplying the scanning signals; and

a data driver for changing the modification gray signals into corresponding data voltages and outputting the image signals,

wherein the one or more modification parameters are at least one of a temperature, an image quality selected by a user, and an environment of the LCD.

2. The LCD of claim 1, wherein the data gray signal modifier comprises:

a frame storage device for receiving the gray signals from the data gray signal source, storing the gray signals for a period of one frame, and outputting the same;

a controller for controlling writing and reading the gray signals of the frame storage device; and

a data gray signal converter for considering the gray signals of a present frame transmitted by the data gray signal source and the gray signals of a previous frame transmitted by the frame storage device, and outputting the modification gray signals.

3. The LCD of claim 2, wherein the data gray signal converter comprises:

a storage device for storing a modification value to modify the data gray signal according to the one or more modification parameter;

a look-up table (LUT) selector for setting an ID of an LUT, the ID representing a selected LUT from the storage device, the LUT selector further setting a coefficient value for converting modification values of the selected LUT based on the one or more modification parameters;

an LUT converter for reading the selected LUT from the storage device, the LUT converter further converting the modification values of the selected LUT according to the coefficient value, thereby outputting a modification LUT therefrom and;

a modification parameter input unit for reading modification values corresponding to gray signals of present and previous frames from the selected LUT or the modification LUT, and thereby generating modification gray signals based upon the modification values.

4. The LCD of claim 1, wherein each compensation value of an LUT is represented by G_ij, the present frame gray signal G_n matching with G_ij is expressed as G_n=(i−

1)×

2<sup>8−

y</sup>, and the previous frame gray signal G<sub>n−

1</sub> matching with G_ij is expressed as G<sub>n−

1</sub>=(j−

1)×

2<sup>8−

y</sup>.

5. The LCD of claim 4, wherein the LUT converter modifies the compensation value G_ij of the selected LUT so as to produce a compensation value G_ij corresponding to a present temperature that satisfies the following equation when the present temperature does not correspond to a predetermined temperature:

G_ij′

=G+α

(G_ij−

G_ii)+β

(G_ij−

G_ii)²+γ

(G_ij−

G_ii)⁴+ . . .

where G_ii=(i−

1)×

2<sup>8−

y</sup>, and

α

, β

, and γ

are parameters for compensating the difference between the present temperature and the predetermined temperature.

6. The LCD of claim 5, wherein the LUT converter sets the value of the modification coefficient to begreater than 1 when the present temperature is lower than the predetermined temperature, and sets the value of the modification coefficient to be less than 1 when the present temperature is higher than the predetermined temperature.

7. The LCD of claim 2, wherein the data gray signal converter comprises:

a look-up table (LUT) for outputting variables (f, a, and b) for compensating a moving image by considering an x-bit gray signal of a present frame transmitted by the data gray signal source and y-bit gray signals of a previous frame transmitted by the frame storage device; and

a calculator for generating and outputting the modification gray signals using the data gray signal of a previous frame, a z-bit LSB of the x-bit gray signal of a present frame, and variables f, a, and b;

wherein f=(G_n, G<sub>n−

1</sub>) and is a compensation value according to the gray signal of the previous frame and the gray signal at the present frame, and wherein a and b are integers representing the difference between the compensation value of the present pixel and the compensation values of the neighboring pixel.

8. The LCD of claim 7, wherein the LUT converter modifies the variables a and b that satisfy the following equation according to the selected LUT when the present temperature does not correspond to the predetermined temperature:

9. The LCD of claim 7, wherein the modified gray data G_n′

are obtained using the equation

10. The LCD of claim 7, wherein a clock signal frequency synchronized with the gray signal provided by the data gray signal source is identical with that synchronized with the controller.

11. The LCD of claim 2, wherein a clock signal frequency synchronized with the gray signal provided by the data gray signal source is different from that synchronized with the controller.

12. The LCD of claim 2, wherein the LCD further comprises:

a combiner for receiving the gray signals from the data gray signal source, combining the gray signals to be synchronized with a clock signal frequency with which the controller is synchronized, and outputting the combined gray signals to the frame storage device and the data gray signal converter; and

a divider for dividing the gray signals output by the data gray signal converter so as to be synchronized with a frequency with which the gray signals transmitted by the data gray signal source are synchronized.

13. The LCD of claim 2, wherein the data gray signal converter modifies the gray signals so as to output a modification data voltage V_n′

that satisfies the following equation;

|V_n′

|=|V_n|+f(|V_n|−

|V<sub>n−

1</sub>|)

where the data voltage of the present frame is set to be V_n, and that of the previous frame is set to be V<sub>n−

1</sub>.

14. The LCD of claim 6, wherein the modification parameter is transmitted from a data source as a gray signal during a data blank period.

15. A method for driving a liquid crystal display (LCD), the LCD having a plurality of gate lines, a plurality of data lines insulated from and crossing the gate lines, and a plurality of pixels formed in an area surrounded by the gate lines and data lines and arranged as a matrix pattern and having switching elements connected to the gate lines and data lines, the method comprising:

(a) sequentially supplying scanning signals to the gate lines;

(b) receiving image signals from an image signal source, and generating modification image signals from image signals of present and previous frames in accordance with one or more modification parameters; and

(c) supplying data voltages corresponding to the generated modification image signals to the data lines,

wherein the one or more modification parameters are at least one of a temperature, an image quality selected by a user, and an environment of the LCD.

16. The LCD driving method of claim 15, wherein the image signals are identified as digital gray signals.

17. The LCD driving method of claim 15, wherein said generating modification image signals further comprises:

applying on a conversion table having modification values matching with the previous frame image signal and the present image signal; and

generating a new conversion table by converting the modification values according to a particular modification parameter when the conversion table corresponding to the particular modification parameter does not exist, and generating the modification image signals based on the new conversation table.

18. The LCD driving method of claim 15, wherein the converting of the conversion table is performed during a data blank period.