Devices and methods for reduction of display to touch crosstalk

• US 9,626,046 B2
• Filed: 09/24/2013
• Issued: 04/18/2017
• Est. Priority Date: 09/24/2013
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Stronks, David A., Al-Dahle, Ahmad, Yao, Wei H.
• Primary Examiner(s): EURICE, MICHAEL
• Application Number:
  US14/035,104
• Publication Number:
  US 20150084911A1
• Time in Patent Office: 1,302 Days
• CPC Class Codes: G02F 1/13606 having means for reducing parasitic capacitance
• CPC Class Codes: G02F 1/13624 having more than one switching element per pixel
• CPC Class Codes: G06F 2203/04107 Shielding in digitiser, i.e. guard or shielding arrangements, mostly for capacitive touchscreens, e.g. driven shields, driven grounds
• CPC Class Codes: G06F 3/0412 Digitisers structurally integrated in a display
• CPC Class Codes: G06F 3/0418 for error correction or compensation, e.g. based on parallax, calibration or alignment
• 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
• CPC Class Codes: G09G 2300/0847 being a dynamic memory without any storage capacitor, i.e. with use of parasitic capacitances as storage elements
• CPC Class Codes: G09G 2320/0209 Crosstalk reduction, i.e. to reduce direct or indirect influences of signals directed to a certain pixel of the displayed image on other pixels of said image, inclusive of influences affecting pixels in different frames or fields or sub-images which constitute a same image, e.g. left and right images of a stereoscopic display
• CPC Class Codes: G09G 3/20 for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
• CPC Class Codes: G09G 3/3655 Details of drivers for counter electrodes, e.g. common electrodes for pixel capacitors or supplementary storage capacitors

Abstract

Devices and methods for reducing display-to-touch crosstalk are provided. In or more examples, an electronic display panel may include a pixel. The pixel may include a pixel electrode, a common electrode, and a first transistor having a first source coupled to a data line, a first gate coupled to a gate line, and a first drain coupled to the pixel electrode. The pixel may also include a second transistor having a second source coupled to the common electrode, a second gate coupled to the gate line, and a second drain coupled to a common voltage source. The second transistor may be configured to cause a parasitic capacitance between the gate line and the second drain of the second transistor and to reduce an effect of a parasitic capacitance between the gate line and the first drain of the first transistor.

Claims

1. A display panel, comprising:

a unit pixel, including;

a unit pixel electrode;

a first common electrode;

a first transistor having a first source coupled to a data line, a first gate coupled to a gate line, and a first drain coupled to the unit pixel electrode, wherein the first transistor is configured to pass a data signal from the data line to the unit pixel electrode upon receipt of an activation signal from the gate line; and

a second transistor having a second source coupled to the first common electrode, a second gate coupled to the gate line, and a second drain coupled to a common voltage source, wherein the second transistor is configured to cause a parasitic capacitance between the gate line and the second drain of the second transistor and to reduce an effect of a parasitic capacitance between the gate line and the first drain of the first transistor;

wherein the first common electrode of the unit pixel is configured to operate, while in a touch mode, as a touch sense electrode that detects a touch capacitance formed between the first common electrode and a second common electrode of another unit pixel, wherein the second common electrode is configured to operate, in the touch mode, as a touch drive electrode, wherein the touch capacitance is indicative of a touch or hover over the display panel.

2. The display panel of claim 1, wherein the first transistor is configured to pass displayable image data as the data signal to the unit pixel electrode.

3. The display panel of claim 1, wherein the second transistor is configured to receive a control signal to switch between one of an activated state or a deactivated state to control a voltage on the first common electrode, and wherein, in the deactivated state, the second drain of the second transistor is configured to allow the common voltage signal to charge the parasitic capacitance.

4. The display panel of claim 1, comprising a third transistor, wherein the first common electrode is communicatively coupled to the second drain of the second transistor and the second common electrode is communicatively coupled to a third drain of the third transistor, and wherein the parasitic capacitance is formed along a conductive path between the first common electrode and the second common electrode.

5. The display panel of claim 1, wherein the second transistor is configured to transmit a common voltage signal to the first common electrode upon receipt of a second activation signal from the gate line, and wherein the second transistor is configured to not transmit the common voltage signal when deactivated.

6. The display panel of claim 5, wherein, in a display mode, the second transistor is configured to transmit the common voltage signal to the first common electrode at substantially the same time the first transistor is configured to pass the data signal to the unit pixel electrode.

7. The display panel of claim 5, wherein, in a touch mode, the first transistor and the second transistor are configured to deactivate, during which time the display panel is configured to detect one or more touches or hovers on the display panel.

8. An electronic device, comprising:

a liquid crystal display (LCD) panel comprising a plurality of unit pixels, wherein each of the plurality of unit pixels comprises a first transistor, a second transistor, and a unit pixel electrode formed there between;

a gate driver configured to transmit a signal to switch the first transistor and the second transistor to one of an activated state or a deactivated state, wherein, in the activated state, the first transistor is configured to supply image data to the unit pixel electrode; and

a touch controller configured to generate a touch drive signal to stimulate one or more touch drive voltage common (VCOM) electrodes and to receive a touch sense signal from one or more touch sense VCOM electrodes as an indication of a touch or hover of the LCD, wherein the second transistor is configured to substantially reduce an effect of a capacitive coupling between the unit pixel electrode and the touch drive signal or between the unit pixel electrode and the touch sense signal, and wherein the touch sense signal is configured to vary based on a touch capacitance formed between the one or more touch drive VCOM electrodes and the one or more touch sense VCOM electrodes.

9. The electronic device of claim 8, wherein the plurality of unit pixels comprises an array of display pixels.

10. The electronic device of claim 8, wherein the plurality of unit pixels comprises an array of touch pixels.

11. The electronic device of claim 8, wherein the gate driver is configured to transmit the signal to switch the first transistor and the second transistor to the deactivated state, and wherein the touch controller is configured to generate the touch drive signal to stimulate the one or more touch drive VCOM electrodes when the first transistor and the second transistor are each in the deactivated state.

12. The electronic device of claim 8, wherein a change in the capacitance comprises an indication of the touch or hover of the LCD.

13. The electronic device of claim 8, wherein, in the activated state, the second transistor is configured to pass a common voltage signal to a common electrode formed between the first transistor and the second transistor, wherein the unit pixel electrode and the common electrode are configured to form a liquid crystal capacitance.

14. A method of reducing display-to-touch crosstalk, comprising:

in a display mode of operation;

supplying an activation signal to a first active switching device of a display pixel of an electronic display, wherein the first active switching device is configured to control a data signal supplied to a unit pixel electrode of the display pixel;

supplying an activation signal to a second active switching device of the display pixel, wherein the second active switching device is configured to control a common voltage signal supplied to a common electrode of the display pixel; and

in a touch mode of operation;

deactivating the second active switching device, wherein deactivating the second active switching device comprises substantially reducing an effect of an occurrence of a parasitic capacitance between a gate line of the display pixel and a first common voltage (VCOM) electrode used in touch sensing in the electronic display; and

supplying a touch drive signal to the touch pixel to stimulate the touch pixel.

15. The method of claim 14, wherein supplying the activation signal to the first active switching device comprises activating the first active switching device to store image data to the unit pixel electrode.

16. The method of claim 14, wherein deactivating the second active switching device comprises deactivating the second active switching following a period of time in which the data signal is supplied to the unit pixel electrode.

17. The method of claim 14, wherein deactivating the second active switching) The method of claim 14, wherein reducing the occurrence of the parasitic capacitance between the display pixel and the touch pixel comprises reducing a dependence of the parasitic capacitance on a voltage of the unit pixel electrode.

18. The method of claim 14, comprising:

receiving a touch sense signal from the touch pixel; and

determining a touch or hover of the electronic display based on the received touch sense signal, wherein a touch drive signal and the touch sense signal are substantially unmitigated by the parasitic capacitance.

19. An electronic device, comprising:

a first thin-film transistor (TFT) of a unit pixel, wherein the first TFT comprises a first source, a first gate, and a first drain, wherein the first TFT is configured to transmit an image data signal from the first source to the first drain;

a second TFT of the unit pixel, wherein the second TFT comprises a second source, a second gate, and a second drain, wherein the second TFT is configured to transmit a common voltage signal from the second drain to the second source, wherein the first TFT is communicatively coupled to the second TFT, and wherein the first drain of the first TFT and the second source of the second TFT are configured to form a liquid crystal capacitance therebetween to store image data thereto; and

a row common voltage (VCOM) electrode and a column common voltage (VCOM) electrode coupled to the first TFT and the second TFT, wherein a touch capacitance is formed along a first conductive path between row VCOM electrode and the column VCOM electrode, and wherein a parasitic capacitance is formed along a second conductive path between row VCOM electrode and the column VCOM electrode to reduce any effect of another parasitic capacitance that may form along the first conductive path.

20. The electronic device of claim 19, wherein the second TFT is configured such that the common voltage signal on the second drain of the second TFT charges the parasitic capacitance in lieu of the image data signal on the first drain of the first TFT.

21. The electronic device of claim 19, wherein the touch capacitance is configured to provide an indication of a touch or hover of a display of the electronic device.