Display guarding techniques

• US 9,465,482 B2
• Filed: 03/02/2015
• Issued: 10/11/2016
• Est. Priority Date: 10/01/2013
• Status: Active Grant

• Current Assignee: Synaptics Incorporated
• Original Assignee: Synaptics Incorporated
• Inventors: Ludden, Christopher A.
• Primary Examiner(s): Bukowski, Kenneth
• Application Number:
  US14/635,927
• Publication Number:
  US 20150193082A1
• Time in Patent Office: 589 Days
• Field of Search: None
• US Class Current: 1/1
• CPC Class Codes: G02F 1/13338 Input devices, e.g. touch panels
• 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 3/04184 Synchronisation with the driving of the display or the backlighting unit to avoid interferences generated internally
• CPC Class Codes: G06F 3/0443 using a single layer of sensing electrodes
• CPC Class Codes: G06F 3/0445 using two or more layers of sensing electrodes, e.g. using two layers of electrodes separated by a dielectric layer
• 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 2330/06 Handling electromagnetic interferences [EMI], covering emitted as well as received electromagnetic radiation

Abstract

Embodiments described herein mitigate the effect of a coupling capacitance between a sensor electrode in a touch sensor and a display electrode in a display screen. An input device, which includes the touch sensor and display screen, may transmit a guarding signal on the display electrodes when performing capacitive sensing. In one embodiment, the guarding signal may have similar characteristics as a modulated signal (e.g., similar amplitude and/or phase) driven on the sensor electrode to detect interaction between the input device and an input object. By driving a guarding signal that is similar to the modulated signal onto the display electrodes, the voltage difference between the sensor electrode and display electrode remains the same. Accordingly, the coupling capacitance between the sensor electrode and the display electrode does not affect a capacitance measurement used to detect the user interaction.

Claims

1. An input device comprising:

a plurality of sensor electrodes each comprising at least one of a plurality of common electrodes of a display, wherein the plurality of common electrodes are configured for display updating and capacitive sensing;

a plurality of display electrodes; and

a processing system coupled to the plurality of sensor electrodes and the plurality of display electrodes, the processing system is configured to;

drive a modulated signal onto a first sensor electrode of the plurality of sensor electrodes to acquire a change of capacitance during a first period, and

operate a first display electrode of the plurality of display electrodes in a guard mode to mitigate an effect of a coupling capacitance between the first sensor electrode and the first display electrode during the first period, wherein mitigating the effect of the coupling capacitance comprises maintaining a constant voltage difference between the first sensor electrode and the first display electrode during the first period.

2. The input device of claim 1, wherein the processing system is configured to, when operating the first display electrode in the guard mode, drive the first display electrode with a guarding signal.

3. The input device of claim 2, wherein the guarding signal and the modulated signal are similar in at least one of phase, amplitude and frequency.

4. The input device of claim 1, wherein the processing system is configured to, when operating the first display electrode in the guard mode, electrically float the first display electrode.

5. The input device of claim 1, wherein the first display electrode is a source electrode.

6. The input device of claim 1, wherein the first display electrode is a gate electrode.

7. The input device of claim 1, wherein the processing system is further configured to operate a second display electrode of the plurality of display electrodes in the guard mode during the first period.

8. The input device of claim 7, wherein the processing system is configured to, when operating the first display electrode in the guard mode, drive the first display electrode with a guarding signal and electrically float the second display electrode.

9. The input device of claim 8, wherein the first display electrode is a source electrode and the second display electrode is a gate electrode.

10. The input device of claim 1, wherein the processing system is configured to drive a second one of the plurality of sensor electrodes with a guarding signal during the first period.

11. The input device of claim 1, wherein the plurality of sensor electrodes are disposed in a common layer.

12. The input device of claim 1, wherein the processing system comprises a first controller configured to drive the modulated signal onto the first sensor electrode and a second controller configured operate the first display electrode in the guard mode.

13. The input device of claim 12, wherein the first controller is synchronized with the second controller.

14. The input device of claim 1, wherein the processing system comprises a controller configured to drive the modulated signal onto the first sensor electrode and configured to operate the first display electrode in the guard mode.

15. A processing system for an input device comprising:

a sensor module comprising sensor circuitry, wherein the sensor module is configured to be coupled to a plurality of sensor electrodes and is configured to drive, during a first time period, a first sensor electrode of the plurality of sensor electrodes with a modulated signal for capacitive sensing, wherein each sensor electrode of the plurality of sensor electrodes comprise at least one of a plurality of common electrodes, wherein the plurality of common electrodes is configured for updating a display of a display device and for capacitive sensing, wherein the first sensor electrode of the plurality of sensor electrodes is capacitively coupled with a first display electrode of a plurality of display electrodes and wherein the first display electrode is configured to be operated in a guard mode during the first time period such that that a voltage difference between the first sensor electrode and the first display electrode remains constant during the first time period.

16. The processing system of claim 15, wherein the sensor module, when operating the first display electrode in the guard mode, is configured to drive the first display electrode with a guarding signal.

17. The processing system of claim 16, wherein the sensor module, when operating the first display electrode in the guard mode, is configured to electrically float the first display electrode.

18. A processing system for a display device, the processing system comprising:

a display driver module comprising display driver circuitry configured for coupling to a plurality of display electrodes, the display driver module configured to;

drive a first display electrode of the plurality of display electrodes for display updating, wherein the first display electrode is capacitively coupled to a first sensor electrode, and operate the first display electrode in a guard mode during a first period such that a voltage difference between the first display electrode and the first sensor electrode remains constant during the first period.

19. The processing system of claim 18, wherein the processing system further comprises:

a sensor module coupled to a plurality of sensor electrodes, the sensor module configured to drive the first sensor electrode with a modulated signal for capacitive sensing.

20. The processing system of claim 19, wherein the display driver module, when operating the first display electrode in the guard mode, is further configured to drive the first display electrode with a guarding signal, wherein the modulated signal and the guarding signal have at least one of a similar phase, amplitude and frequency.