INTEGRATED TOUCH SCREEN

• US 20110050585A1
• Filed: 08/25/2009
• Published: 03/03/2011
• Est. Priority Date: 08/25/2009
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Yousefpor, Marduke, Chang, Shih Chang, Zhong, John Z., Hotelling, Steven Porter
• Granted Patent: US 8,390,582 B2
• Time in Patent Office: Days
• US Class Current: 345/173
• CPC Class Codes: G06F 3/0412 Digitisers structurally integrated in a display
• CPC Class Codes: G06F 3/0443 using a single layer of sensing electrodes
• CPC Class Codes: G06F 3/0446 using a grid-like structure of electrodes in at least two directions, e.g. using row and column electrodes

Abstract

Displays with integrated touch sensing circuitry are provided. An integrated touch screen can include multi-function circuit elements that form part of the display circuitry of the display system that generates an image on the display, and also form part of the touch sensing circuitry of a touch sensing system that senses one or more touches on or near the display. The multi-function circuit elements can be, for example, capacitors in display pixels of an LCD that are configured to operate as display circuitry in the display system, and that may also be configured to operate as touch circuitry of the touch sensing system. For example, one or more circuit elements of the display pixel stackup can form a conductive portion of the touch sensing system, such as a charge collector, which can be operated with switches and conductive lines to sense touch.

Claims

1. A touch screen comprising:

a group of display pixels, each display pixel including display circuitry that includes a circuit element; and

touch sensing circuitry in one or more of the display pixels including

a conductive portion that includes one of the circuit elements,

first and second conductive lines, each of the first and the second conductive lines extending from the display pixel to an outer edge of the group of display pixels,

a first switch that connects and disconnects the first conductive line to the conductive portion, and

a second switch that connects and disconnects the second conductive line to the conductive portion.

2. The touch screen of claim 1, wherein the circuit elements include common electrodes.

3. The touch screen of claim 1, wherein each of the first conductive lines is electrically connected to a plurality of first switches.

4. The touch screen of claim 1, wherein the second conductive lines include data lines of the display circuitry.

5. The touch screen of claim 1, wherein the first switch is a thin film transistor.

6. A touch screen system including the touch screen of claim 1, and further comprising:

a voltage drive that outputs a voltage to the second conductive line;

a switch controller that controls the first and second switches in accordance with the output voltage to generate a charge on the conductive portion, wherein an amount of charge generated is based on an amount of touch proximate to the conductive portion, and to transfer the charge to the first conductive line; and

a charge sensing circuit that detects the amount of charge transferred to the first conductive line.

7. The touch screen system of claim 6, wherein the switch controller controls the first and second switches to connect the second conductive line to, and to disconnect the first conductive line from, the conductive portion when the voltage drive outputs the voltage, and controls the first and second switches to disconnect the second conductive line from, and to connect the first conductive line to, the conductive portion to transfer the amount of charge generated by the voltage to the first conductive line.

8. The touch screen of claim 1, wherein the conductive portion includes the circuit element of a first display pixel electrically connected by a bridge to the circuit element of a second display pixel.

9. The touch screen of claim 8, wherein the first and second display pixels are adjacent to each other.

10. The touch screen of claim 8, wherein the first switch is located in the first display pixel and the second switch is located in the second display pixel.

11. A touch screen comprising:

a group of display pixels, each display pixel including display circuitry that includes a circuit element; and

touch sensing circuitry in one or more of the display pixels including

a capacitive sensor circuitry that includes a charge collector and first and second conductive lines connected to the charge collector by first and second switches, respectively, wherein at least a portion of one of the charge collector, the first conductive line, the second conductive line, the first switch, and the second switch includes the circuit element.

12. The touch screen of claim 11, wherein the first and second switches perform non-overlapping switching of the charge collector.

13. The touch screen of claim 11, wherein the charge collector includes common electrodes of the display pixels.

14. The touch screen of claim 13, wherein the charge collector further includes conductive structures that connect the common electrodes, the conductive structures being formed in a plane of the common electrodes.

15. A computer system comprising:

a processor;

a memory;

a display system including a group of display pixels, each display pixel including display circuitry that includes a circuit element; and

touch sensing circuitry in one or more of the display pixels including a conductive portion that includes one of the circuit elements, first and second conductive lines, each of the first and the second conductive lines extending from the display pixel to an outer edge of the group of display pixels, a first switch that connects and disconnects the first conductive line to the conductive portion, and a second switch that connects and disconnects the second conductive line to the conductive portion.

16. A method of reducing a parasitic capacitance at a drain of a transistor in a capacitive touch sensing system, the method comprising:

applying a first alternating current (AC) voltage to a source of the transistor; and

applying a second AC voltage to a gate of the transistor, such that a constant gate to source voltage of the transistor is maintained while the source voltage is changing.

17. The method of claim 16, wherein the second AC voltage is generated by bootstrapping.