Active matrix liquid crystal display apparatus and method for flicker compensation

• US 6,429,841 B1
• Filed: 07/15/1999
• Issued: 08/06/2002
• Est. Priority Date: 08/11/1998
• Status: Expired due to Term

• Current Assignee: LG Display Co., Ltd.
• Original Assignee: LG Philips LCD Company Limited (LG Display Co., Ltd.)
• Inventors: Lee, Hyun Chang
• Primary Examiner(s): Lao, Lun-Yi
• Application Number:
  US09/353,855
• Time in Patent Office: 1,118 Days
• Field of Search: 345/147, 345/211, 345/58, 345/87, 345/88, 345/89, 345/90, 345/100, 345/208, 345/690, 345/691, 345/94, 345/92, 345/98
• US Class Current: 345/89
• CPC Class Codes: G09G 2300/0434 Flat panel display in which a field is applied parallel to the display plane
• CPC Class Codes: G09G 2320/0219 Reducing feedthrough effects in active matrix panels, i.e. voltage changes on the scan electrode influencing the pixel voltage due to capacitive coupling
• CPC Class Codes: G09G 2320/0233 Improving the luminance or brightness uniformity across the screen
• CPC Class Codes: G09G 2320/0247 Flicker reduction other than flicker reduction circuits used for single beam cathode-ray tubes
• CPC Class Codes: G09G 3/3648 using an active matrix G09G3/367 - G09G3/3696 take precedence
• CPC Class Codes: G09G 3/3688 suitable for active matrices only
• CPC Class Codes: G09G 3/3696 Generation of voltages supplied to electrode drivers

Abstract

In active matrix liquid crystal display apparatus that is suitable for eliminating a flicker and a residual image, when a source signal having the same gray level is applied to at least two liquid crystal cells in liquid crystal cells on a liquid crystal panel including the liquid crystal cells arranged in a matrix pattern, source lines and reference voltage lines for applying each liquid crystal cell to an electric field, a difference between a source signal applied to each of at least two liquid crystal cells and a reference voltage signal becomes different. A gamma voltage generator is used to compensate the difference in the applied signal to substantially eliminate the flickering and residual image effects.

Claims

1. A liquid crystal display comprising:

a data driver;

a plurality of data lines connected to the data driver;

a gate driver;

a plurality of gate lines connected to the gate driver; and

a voltage generator coupled to the data driver to compensate input signals to the plurality of data lines, wherein the voltage generator provides a first offset voltage to a first one of the plurality of data lines and provides a second offset voltage to a second one of the plurality of data lines, in which the first and second ones of the plurality of data lines are spatially separated with the first one being closer to the gate driver than the second one, and wherein the first offset voltage differs from the second offset voltage in response to a separation distance between the first one and second one of the plurality of data lines when the first and second data lines input an identified gray level of data;

wherein the reference voltage generator is connected to a first location of the shared line and generates higher reference voltages as gate lines that are spatially farther away from the data driver are enable.

2. The liquid crystal display of claim 1, further including a reference voltage generator having an output connected to a plurality of output lines through a shared line, wherein the output lines are extended from the shared line in substantially parallel to the plurality of gate lines.

3. The liquid crystal display of claim 2, wherein the reference voltage generator includes:

a counter; and

a voltage divider connected between a first voltage and a second voltage and further connected to the counter to output different voltages in response to the counter.

4. The liquid crystal display of claim 2, wherein the voltage generator allows a difference between a positive and negative data center value of a source signal applied to each of at least two liquid crystal cells and a reference voltage signal from the reference voltage generator when a source signal having the same gray level is applied to the at least two liquid crystal cell to have a different value.

5. The liquid crystal display of claim 1, wherein when the input signals to the first and second ones of the plurality of data lines are substantially identical, the first and second ones of the plurality of data lines compensated by the first and second offset voltages.

6. The liquid crystal display of claim 1, wherein the first voltage offset is less than the second voltage offset.

7. The liquid crystal display of claim 6, wherein the voltage generator provides a third offset voltage to a third one of the plurality of data lines, wherein the third one of the plurality of data lines is closer to the gate driver than both the first and second ones of the plurality of data lines, and wherein the third voltage offset is greater than the second voltage offset.

8. A display method for a liquid crystal display, comprising the steps of:

providing a data driver;

providing a plurality of data lines connected to the data driver;

providing a gate driver;

providing a plurality of gate lines connected to the gate driver; and

providing a voltage generator coupled to the data driver to compensate input signals to the plurality of data lines, wherein the voltage generator provides a first offset voltage to a first one of the plurality of data lines and provides a second offset voltage to a second one of the plurality of data lines, in which the first and second ones of the plurality of data lines are spatially separated with the first one being closer to the gate driver than the second one, and wherein the first offset voltage differs from the second offset voltage in response to a separation distance between the first one and second one of the plurality of data lines when the first and second data lines input an identified gray level of data;

wherein the reference voltage generator is connected to a first location of the shared line and generates higher reference voltages as gate lines that are spatially farther away from the data driver are enabled.

9. The display method of claim 8, further providing a reference voltage generator having an output connected to a plurality of output lines through a shared line, wherein the output lines are extended from the shared line in substantially parallel to the plurality of gate lines.

10. The display method of claim 9, wherein the voltage generator allows a difference between a positive and negative data center value of a source signal applied to each of at least two liquid crystal cells and a reference voltage signal from the reference voltage generator when a source signal having the same gray level is applied to the at least two liquid crystal cell to have a different value.

11. The display method of claim 9, wherein the reference voltage generator includes:

a counter; and

a voltage divider connected between a first voltage and a second voltage and further connected to the counter to output different voltages in response to the counter.

12. The display method of claim 9, wherein the first voltage offset is less than the second voltage offset.

13. The liquid crystal display of claim 12, wherein the voltage generator provides a third offset voltage to a third one of the plurality of data lines, wherein the third one of the plurality of data lines is closer to the gate driver than both the first and second ones of the plurality of data lines, and wherein the third voltage offset is greater than the second voltage offset.