Kickback Voltage Equalization

• US 20110267283A1
• Filed: 07/23/2010
• Published: 11/03/2011
• Est. Priority Date: 04/30/2010
• Status: Abandoned Application

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: BAE, Hopil, GE, Zhibing, YU, Cheng Ho, CHANG, Shih Chang
• Application Number:
  US12/842,542
• Publication Number:
  US 20110267283A1
• Time in Patent Office: Days
• US Class Current: 345/173
• CPC Class Codes: G06F 3/0418 for error correction or compensation, e.g. based on parallax, calibration or alignment

Abstract

Scanning gate lines in a gate driver system of a touch screen is provided. The gate driver system can include gate lines connected to display pixel transistors, a display driver that can generate first and second gate clock signals including first and second voltage transitions, respectively, and a gate drivers that can receive the first and second gate clock signals via gate clock lines and that can apply gate line signals, based on the gate clock signals, to the gate lines. A first voltage change generated in a common electrode line of the touch screen by the first voltage transition can be reduced by a second voltage change generated in the common electrode by the second voltage transition.

Claims

1. A gate driver system of a touch screen, comprising:

a plurality of gate lines connected to display pixel transistors;

a display driver that generates first and second gate clock signals including first and second voltage transitions, respectively; and

a plurality of gate drivers that receive the first and second gate clock signals via gate clock lines and that apply gate line signals, based on the gate clock signals, to the gate lines, wherein a first voltage change generated in a common electrode line of the touch screen by the first voltage transition is reduced by a second voltage change generated in the common electrode by the second voltage transition.

2. The gate driver system of claim 1, wherein a first time interval between the first and second voltage transitions is based on a first time interval value.

3. The gate driver system of claim 2, wherein the plurality of gate drivers includes a first set of gate drivers positioned at a first side of an active area of the touch screen, and a second set of gate drivers positioned at a second side of the active area opposite the first side, the display driver generates third and fourth gate clock signals including third and fourth voltage transitions, respectively, the gate drivers in the first set receive the first and third gate clock signals, and the gate drivers in the second set receive the second and fourth gate clock signals.

4. The gate driver system of claim 3, wherein time intervals between the third and fourth voltage transitions are based on one of the first time interval value and a second time interval value different from the first time interval value.

5. The gate driver system of claim 4, wherein one or both of the first and second time interval values is a fixed value that is based on a hardware design of the gate driver system.

6. The gate driver system of claim 4, wherein one or both of the first and second time interval values is stored in a computer-readable storage memory of the touch screen and is adjustable within a predetermined range of values.

7. The gate driver system of claim 4, wherein all of the time intervals of a first frame of a display operation of the touch screen are based on the first time interval value, and all of the time intervals of a second frame are based on the second time interval value.

8. The gate driver system of claim 7, wherein the display operation includes repeatedly alternating between a number of first frames and a number of second frames based on a predetermined ratio of first frames to second frames.

9. The gate driver system of claim 4, wherein the time intervals of a first frame of a display operation are based on the first and second time interval values in a predetermined ratio.

10. The gate driver system of claim 3, wherein a third voltage change generated in the common electrode line of the touch screen by the third voltage transition is reduced by a fourth voltage change generated in the common electrode by the fourth voltage transition.

11. A method of scanning gate lines during a display operation of a touch screen, the touch screen including a common electrode line capacitively coupled to first and second gate lines of the touch screen, the method comprising:

applying, to the first gate line, a first gate signal that generates a first voltage change in the common electrode line; and

applying, to the second gate line, a second gate signal that generates a second voltage change that reduces the first voltage change in the common electrode line.

12. The method of claim 11, wherein the first gate signal is based on a first gate clock signal that includes a high-to-low voltage transition that switches a state of display pixel transistors connected to the first gate line, and the second gate signal is based on a second gate clock signal that includes a low-to-high voltage transition that switches the state of display pixel transistors connected to the second gate line.

13. The method of claim 12, wherein the high-to-low and low-to-high voltage transitions occur within an interval of 100 nanoseconds.

14. The method of claim 12, further comprising:

setting a time interval between the high-to-low and low-to-high voltage transitions to a first time interval during a first frame of the display operation, and setting the time interval to a second time interval, different than the first time interval, during a second frame of the display operation.

15. The method of claim 14, wherein setting the time intervals includes setting the first and second time intervals to alternate repeatedly based on a predetermined ratio of frames.

16. The method of claim 12, further comprising:

setting a time interval between the high-to-low and low-to-high voltage transitions to a first time interval for the first and second gate line signals during a first frame of the display operation, and setting the time interval to a second time interval, different than the first time interval, for a third and a fourth gate signals during the first frame.

17. The method of claim 16, wherein setting the time intervals includes setting the first and second time intervals to alternate repeatedly during the first frame based on a predetermined ratio of gate signal pairs.

18. A touch screen comprising:

a plurality of display pixels including

a first display pixel including a first transistor with a gate connected to a first gate line of a plurality of gate lines, a source connected to one of a plurality of data lines, and a drain connected to a first pixel electrode, the pixel electrode being capacitively coupled to a first common electrode line;

a second display pixel including a second transistor with a gate connected to a second gate line of the plurality of gate lines, a source connected to one of the plurality of data lines, and a drain connected to a second pixel electrode, the second pixel electrode being capacitively coupled to the first common electrode line, wherein the first common electrode line is capacitively coupled to the first and second gate lines;

a first gate driver that applies a first gate signal to the first gate line based on a first gate clock signal received from a first gate clock line, the first gate clock signal including a first voltage transition that switches the first transistor from an on state to an off state, wherein the first voltage transition generates a corresponding first voltage change in the first common electrode line for a first period of time; and

a second gate driver that applies a second gate signal to the second gate line based on a second gate clock signal received from a second gate clock line, the second gate clock signal including a second voltage transition that switches the second transistor from an off state to an on state, wherein the second gate clock signal is timed such that the second voltage transition generates a corresponding second voltage change in the first common electrode line during the first time period.

19. The touch screen of claim 18, wherein the first gate driver and the first gate clock line are positioned at opposite sides of an active area of the touch screen from the second gate driver and the second gate clock line.