Display guarding techniques

• US 9,007,343 B1
• Filed: 10/30/2013
• Issued: 04/14/2015
• 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:
  US14/067,792
• Publication Number:
  US 20150091843A1
• Time in Patent Office: 531 Days
• Field of Search: None
• US Class Current: 345/174
• 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 that establish a sensing region of the input device;

at least one display electrode configured to, during display updating, set a voltage associated with a pixel of a display device; and

a processing system coupled to the plurality of sensor electrodes and the at least one display electrode, 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 in capacitive coupling between an input object and the first sensor electrode during a first period, and

drive a guarding signal onto the at least one display electrode to mitigate an effect of a coupling capacitance between the first sensor electrode and the at least one display electrode during the first period,

wherein the modulated signal and the guarding signal have a similar characteristic such that a voltage difference between the first sensor electrode and the first display electrode remains constant during the first period.

2. The input device of claim 1, wherein the guarding signal has a similar phase as the modulated signal.

3. The input device of claim 1, wherein the processing system is coupled to a second display electrode of the display device and electrically floats the second display electrode at a same time as driving the guarding signal onto the at least one display electrode, wherein the second display electrode and the at least one display electrode are capacitively coupled such that the guarding signal propagates on the second display electrode.

4. The input device of claim 1, wherein driving the guarding signal onto the at least one display electrode comprises driving a common electrode of the display device with the guarding signal and electrically floating at least one source electrode of the display device, wherein the guarding signal has a similar phase as the modulated signal.

5. The input device of claim 1, wherein the at least one display electrode is at least one of a source electrode that drives a voltage onto a storage element associated with the pixel, a gate electrode that sets a gate voltage on a transistor associated with the pixel, and a common electrode that provides a reference voltage to the storage element.

6. The input device of claim 1, wherein the plurality of sensor electrodes comprises a first set of sensor electrodes and a second set of sensor electrodes, wherein the first set of sensor electrodes are disposed in a direction orthogonal from a direction of the second set of sensor electrodes.

7. The input device of claim 1, wherein the plurality of sensor electrodes are disposed between a color filter glass of the display device and an input surface of the input device.

8. The input device of claim 1, wherein at least one sensor electrode of the plurality of sensor electrodes comprises at least one common electrode of the display device.

9. The input device of claim 1, wherein the at least one sensor electrode of the plurality of sensor electrodes is disposed between a color filter glass of the display device and an input surface of the input device.

10. The input device of claim 7, wherein the at least one sensor electrode of the plurality of sensor electrodes is disposed between a display material of the display device and a color filter of the display device.

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 11, further comprising:

a grid electrode disposed between at least two sensor electrodes of the plurality of sensor electrodes.

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

14. The input device of claim 1, wherein the sensor module is configured to drive a transmitter signal on a first sensor electrode of the plurality of sensor electrodes and receive a resulting signal on a second sensor electrode of the plurality of sensor electrodes, wherein the resulting signals comprises effects corresponding to the transmitter signal.

15. 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 to drive the guarding signal.

16. The input device of claim 15, wherein the first controller is synchronized with the second controller.

17. 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 drive the guarding signal onto the at least one display electrode.

18. A method for mitigating an effect of a coupling capacitance associated with a display electrode when performing capacitive sensing, the method comprising:

driving a modulated signal onto a first sensor electrode of a plurality of sensor electrodes to detect a change in capacitive coupling between an input object and the first sensor electrode during a first period; and

driving a guarding signal onto the display electrode to mitigate the effect of the coupling capacitance between the first sensor electrode and the display electrode during the first period,

wherein the modulated signal and guarding signal have a similar characteristic such that a voltage difference between the first sensor electrode and the display electrode remains constant during the first period.

19. The method of claim 18, wherein the guarding signal has a similar phase as the modulated signal.

20. The method of claim 18, further comprising:

electrically floating a second display electrode of the display device while driving the guarding signal, wherein the guarding signal has a similar phase as the modulated signal.

21. The method of claim 18, wherein the input object causes a change in capacitive coupling between the first sensor electrode and a second sensor electrode and wherein the guarding signal has a similar phase as the modulated signal.

22. The method of claim 18, wherein the display electrode is at least one of a source electrode that drives a voltage onto a storage element associated with a pixel, a gate electrode that sets a gate voltage on a transistor associated with a pixel, and a common electrode that provides a reference voltage to the storage element.

23. The method of claim 18 further comprising driving the first sensor electrode of the plurality of sensor electrodes with a transmitter signal and receiving resulting signals with a second sensor electrode of the plurality of sensor electrodes to acquire changes in capacitive coupling between the first sensor electrode and the second sensor electrode.

24. A processing system for an input device comprising:

a display driver module comprising display driver circuitry coupled to at least one display electrode and configured to;

drive the at least one display electrode to set a voltage associated with a pixel of a display device, and

drive a guarding signal onto the at least one display electrode to mitigate the effect of the coupling capacitance between a first sensor electrode of a plurality of sensor electrodes and the at least one display electrode during a first time period and wherein, during the first time period, the first sensor electrode is driven with a modulated signal to detect a change in capacitance between the first sensor electrode and an input object,

wherein the modulated signal and the guarding signal have a similar characteristic such that a voltage difference between the first sensor electrode and the at least one display electrode remains constant during the first period.

25. The processing system of claim 24, wherein the processing system further comprises a sensor module coupled to the plurality of sensor electrodes and configured to drive the first sensor electrode with the modulated signal.

26. The processing system of claim 24, wherein the display driver module is synchronized with a sensing module, wherein the sensing module is configured to drive the first sensor electrode with the modulated signal.

27. The processing system of claim 24, wherein the guarding signal has a similar phase as the modulated signal.

28. The processing system of claim 24, wherein the at least one display electrode is at least one of a source electrode that drives a voltage onto a storage element associated with the pixel, a gate electrode that sets a gate voltage on a transistor associated with the pixel, and a common electrode that provides a reference voltage to the storage element.

29. A processing system for an input device comprising:

a sensor module comprising sensor circuitry, wherein the sensor module is coupled to a plurality of sensor electrodes and is configured to drive, during a first time period, one of the plurality of sensor electrodes with a modulated signal to detect a change in capacitive coupling between the one sensor electrode and an input object, wherein the sensor module is coupled to and synchronized with a display driver module that is configured to;

drive a guarding signal onto at least one display electrode to mitigate the effect of a coupling capacitance between the one sensor electrode and the at least one display electrode during the first time period,

wherein the modulated signal and the guarding signal have a similar characteristic such that a voltage difference between the one sensor electrode and the at least one display electrode remains constant during the first period.

30. The processing system of claim 29, wherein the guarding signal has a similar phase as the modulated signal.