Determination and reduction of parasitic capacitance variation due to display noise

• US 9,329,738 B2
• Filed: 09/10/2013
• Issued: 05/03/2016
• Est. Priority Date: 09/10/2012
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Yousefpor, Marduke, Poon, Stephen S.
• Primary Examiner(s): Ghebretinsae, Temesgh
• Assistant Examiner(s): Ketema, Benyam
• Application Number:
  US14/023,118
• Publication Number:
  US 20140071087A1
• Time in Patent Office: 966 Days
• Field of Search: 345/174, 178/18.06
• US Class Current: 1/1
• CPC Class Codes: G06F 3/04184 Synchronisation with the driving of the display or the backlighting unit to avoid interferences generated internally
• CPC Class Codes: G06F 3/044 by capacitive means

Abstract

Embodiments described herein generally take the form of methods and systems for identifying and/or reducing a parasitic capacitance variation in a capacitive integrated touch-sensing module that may arise from proximity to a nearby electronic display.

Claims

1. A method for reducing an overall parasitic capacitance between a display and a capacitive touch-sensing panel, the method comprising:

generating an admittance model of a plurality of parasitic capacitances between conductive lines that form a plurality of pixels in the display;

varying at least one of the plurality of parasitic capacitances in the admittance model to an adjusted capacitance level;

determining if the adjusted capacitance level reduces the overall parasitic capacitance between the display and the capacitive touch-sensing panel in the admittance model; and

modifying at least one of the capacitive touch-sensing panel and the display such that the at least one parasitic capacitance in the display is adjusted to the adjusted capacitance level based on the admittance model.

2. The method of claim 1, wherein the overall parasitic capacitance in the admittance model is an expression of a display to capacitive touch-sensing panel cross-capacitance.

3. The method of claim 2, further comprising representing at least one of the plurality of parasitic capacitances as at least one phasor.

4. The method of claim 3, wherein representing at least one of the plurality of parasitic capacitances as at least one phasor comprises:

representing the capacitance of a touch region in the capacitive touch-sensing panel as a first phasor; and

representing the parasitic capacitance of a nearby display pixel in the display as a second phasor.

5. The method of claim 4, further comprising:

comparing the magnitude of the first phasor to the second phasor; and

determining an impact of the first phasor on the second phasor based on the comparison.

6. The method of claim 4, further comprising:

mapping a structural change in at least one of the display and the capacitive touch-sensing panel to a change in the at least one phasor; and

determining an effect of the structural change on the overall parasitic capacitance based on the mapping.

7. The method of claim 1, wherein modifying at least one of the capacitive touch-sensing panel and the display comprises modifying a doping characteristic of a region of a display pixel in the display.

8. The method of claim 1, wherein modifying at least one of the capacitive touch-sensing panel and the display comprises modifying shielding that shields a display pixel in the display.

9. A method for reducing a cross-capacitance between a display and a touch-sensitive component, the method comprising:

generating an admittance model that includes a plurality of parasitic capacitance values, each of which corresponds to a given parasitic capacitance in the display;

in the admittance model, adjusting at least one of the plurality of parasitic capacitance values;

determining if adjusting the parasitic capacitance value decreases an overall parasitic capacitance value in the admittance model that corresponds to the cross-capacitance between the display and the touch-sensitive component; and

adjusting the given parasitic capacitance in the display to reduce the cross-capacitance between the display and the touch-sensitive component.

10. The method of claim 9, wherein adjusting the at least one of the plurality of parasitic capacitance values comprises adjusting the at least one of the plurality of parasitic capacitance values to an adjusted parasitic capacitance value, and wherein adjusting the given parasitic capacitance in the display comprises adjusting the given parasitic capacitance in the display to the adjusted parasitic capacitance value.

11. The method of claim 10, wherein adjusting the given parasitic capacitance in the display comprises modifying a physical parameter of the display.

12. The method of claim 11, wherein adjusting the given parasitic capacitance in the display comprises modifying a doped region of a thin-film transistor in the display.

13. The method of claim 11, wherein adjusting the given parasitic capacitance in the display comprises modifying shielding that shields a pixel in the display.

14. The method of claim 9, further comprising:

representing the at least one of the parasitic capacitance values as a phasor.

15. The method of claim 9, wherein the touch-sensitive component is integrated into the display.

16. The method defined in claim 15, wherein the display comprises pixels and the touch-sensitive component comprises a plurality of touch-sensitive regions, and wherein the pixels are interspersed with the plurality of touch-sensitive regions.

17. A method for reducing a parasitic capacitance between a display and a capacitive touch-sensing panel, the method comprising:

generating an admittance model of a plurality of parasitic capacitances between a plurality of pixels in the display;

representing one or more of the plurality of parasitic capacitances as one or more phasors;

varying one or more of the plurality of parasitic capacitances in the admittance model;

determining if the variance of the one or more of the plurality of parasitic capacitances reduces an overall parasitic capacitance between the display and the capacitive touch-sensing panel, wherein the overall parasitic capacitance is an expression of a display to touch sensing module cross-capacitance; and

in response to determining that the variance reduces the overall parasitic capacitance, implementing the variance in at least one of the capacitive touch-sensing panel and the display.