Modulating a reference voltage to perform capacitive sensing

• US 10,795,471 B2
• Filed: 06/30/2015
• Issued: 10/06/2020
• Est. Priority Date: 01/05/2015
• Status: Active Grant

• Current Assignee: Synaptics Incorporated
• Original Assignee: Synaptics Incorporated
• Inventors: Reynolds, Joseph Kurth, Morein, Stephen L.
• Primary Examiner(s): Marinelli, Patrick F
• Application Number:
  US14/788,735
• Publication Number:
  US 20160196803A1
• Time in Patent Office: 1,925 Days
• Field of Search: 345174
• CPC Class Codes: G06F 1/263 Arrangements for using multiple switchable power supplies, e.g. battery and AC G06F1/30 takes precedence
• CPC Class Codes: G06F 1/3228 Monitoring task completion, e.g. by use of idle timers, stop commands or wait commands
• CPC Class Codes: G06F 1/3262 Power saving in digitizer or tablet
• CPC Class Codes: G06F 1/3287 by switching off individual functional units in the computer system
• CPC Class Codes: G06F 2203/04101 2.5D-digitiser, i.e. digitiser detecting the X/Y position of the input means, finger or stylus, also when it does not touch, but is proximate to the digitiser's interaction surface and also measures the distance of the input means within a short range in the Z direction, possibly with a separate measurement setup
• CPC Class Codes: G06F 2203/04108 Touchless 2D- digitiser, i.e. digitiser detecting the X/Y position of the input means, finger or stylus, also when it does not touch, but is proximate to the digitiser's interaction surface without distance measurement in the Z direction
• CPC Class Codes: G06F 3/03547 Touch pads, in which fingers can move on a surface
• CPC Class Codes: G06F 3/0412 Digitisers structurally integrated in a display
• CPC Class Codes: G06F 3/0416 Control or interface arrangements specially adapted for digitisers
• CPC Class Codes: G06F 3/0418 for error correction or compensation, e.g. based on parallax, calibration or alignment
• 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: G06F 3/045 using resistive elements, e.g. a single continuous surface or two parallel surfaces put in contact
• CPC Class Codes: G09G 2300/023 Display panel composed of stacked panels
• CPC Class Codes: G09G 2300/0426 Layout of electrodes and connections
• CPC Class Codes: G09G 2330/021 Power management, e.g. power saving
• 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: Y02D 10/00 Energy efficient computing, e.g. low power processors, power management or thermal management

Abstract

This disclosure generally provides an input device that includes a reference voltage modulator that modulates reference voltage rails when performing capacitive sensing. In one embodiment, reference voltage rails are coupled to a DC power source which provides power to operate a panel that includes a display screen integrated with a touch sensing region. Before performing capacitive sensing, the input device may isolate the DC power source from the reference voltage rails and use the reference voltage rails to modulate the rails—e.g., V_DD and V_GND. The input device may include a receiver that simultaneously acquires resulting signals from a plurality of display and/or sensor electrodes when modulating the reference voltage rails. The resulting signals can then be processed to determine if an input object is interacting with the input device.

Claims

1. An input device, comprising:

a plurality of display electrodes comprising common electrodes and source electrodes;

a plurality of sensor electrodes;

a processing system, comprising;

a reference voltage modulator configured to modulate reference voltage rails during a first time period, wherein the processing system is configured to;

drive the plurality of display electrodes to update a display during a second time period that is non-overlapping with the first time period, wherein the reference voltage rails are held at unmodulated, constant voltages during the second time period, and

acquire resulting signals from the plurality of sensor electrodes driven with a capacitive sensing signal while the reference voltage rails are modulated during the first time period, wherein the capacitive sensing signal is derived from modulating the reference voltage rails; and

source drivers coupled to the source electrodes, wherein the source drivers are configured to drive the source electrodes to update the display during the second time period while the reference voltage rails are held at the unmodulated, constant voltages, wherein, during the first time period and while the reference voltage rails are modulated, the source electrodes are guarded.

2. The input device of claim 1, wherein the reference voltage rails are capacitively coupled.

3. The input device of claim 1, wherein the source electrodes are guarded by driving the source electrodes with the capacitive sensing signal derived from modulating the reference voltage rails.

4. The input device of claim 1, further comprising:

gate electrodes for updating the display, wherein, when driving the capacitive sensing signal onto the source electrodes the gate electrodes are floated.

5. The input device of claim 1, further comprising:

a power management controller configured to receive the reference voltage rails when updating the display when the reference voltage rails are unmodulated and convert the reference voltage rails into power voltages for powering display circuitry in a display panel comprising the display.

6. The input device of claim 5, wherein the power management controller is in a low-power state when the reference voltage modulator modulates the reference voltage rails and an active state when a display module updates the display, and wherein in the active state the power management controller draws more power than in the low-power state.

7. The input device of claim 1, wherein a receiver is configured to simultaneously acquire second resulting signals from both the plurality of display electrodes and the plurality of sensor electrodes.

8. The input device of claim 1, further comprising:

a backlight, wherein the reference voltage modulator is configured to modulate the reference voltage rails when the backlight and the display are turned off.

9. The input device of claim 1, further comprising:

a display source;

a display panel; and

a first data interface disposed on a same integrated circuit as the reference voltage modulator, the first data interface is configured to communicate with the display source to receive display data for updating the display, wherein the first data interface is part of an unmodulated voltage domain comprising power voltage rails that remain unmodulated when the reference voltage rails are modulated by the reference voltage modulator.

10. A processing system, comprising:

a reference voltage modulator configured to modulate reference voltage rails during a first time period;

a receiver configured to acquire resulting signals with a plurality of sensor electrodes driven with a capacitive sensing signal while the reference voltage rails are modulated during the first time period, wherein the capacitive sensing signal is derived from modulating the reference voltage rails;

a display module configured to;

drive a plurality of display electrodes to update a display during a second time period that is non-overlapping with the first time period, wherein the reference voltage rails are held at unmodulated, direct current (DC) voltages during the second time period; and

source drivers coupled to source electrodes, wherein the source drivers are configured to drive the source electrodes to update the display during the second time period while the reference voltage rails are held at the unmodulated, DC voltages, wherein, during the first time period and while reference voltage rails are modulated, the source electrodes are guarded.

11. The processing system of claim 10, wherein the reference voltage rails are capacitively coupled.

12. The processing system of claim 10, further comprising:

a power management controller configured to;

receive the reference voltage rails when updating the display when the reference voltage rails are unmodulated; and

convert the reference voltage rails into power voltages for powering display circuitry in a display panel comprising the display.

13. The processing system of claim 12, wherein the power management controller is in a low-power state when the reference voltage modulator modulates the reference voltage rails and an active state when the display module updates the display, and wherein in the active state the power management controller draws more power than in the low-power state.

14. The processing system of claim 10, wherein the receiver is configured to simultaneously acquire second resulting signals from both the plurality of display electrodes and the plurality of sensor electrodes.

15. The processing system of claim 10, wherein the processing system is configured to modulate the reference voltage rails when a backlight and the display being off.

16. The processing system of claim 10, further comprising:

a first data interface disposed on a same integrated circuit as the reference voltage modulator, the first data interface is configured to communicate with a display source to receive display data for updating the display, wherein the first data interface is part of an unmodulated voltage domain comprising power voltage rails that remain unmodulated when the reference voltage rails are modulated by the reference voltage modulator.

17. A method, comprising:

updating pixels in a display of an input device by driving a plurality of source electrodes during a first time period while holding reference voltage rails at unmodulated, direct current (DC) voltages during the first time period;

modulating the reference voltage rails during a second time period that is non-overlapping with the first time period, wherein source drivers coupled to a plurality of sensor electrodes drive a capacitive sensing signal onto the plurality of sensor electrodes for capacitive sensing during the second time period, wherein the capacitive sensing signal is derived from modulating the reference voltage rails, and wherein, during the second time period and while the reference voltage rails are modulated, the plurality of source electrodes are guarded; and

acquiring resulting signals from a plurality of sensor electrodes driven with the capacitive sensing signal while the reference voltage rails are modulated during the second time period.

18. The method of claim 17, wherein the input device is in a low-power state during the second time period, the method further comprising:

after detecting an input object based on the resulting signals;

switching the input device from the low-power state to an active state; and

ceasing to modulate the reference voltage rails, and wherein in the active state the input device draws more power than in the low-power state.

19. The method of claim 17, further comprising:

before modulating the reference voltage rails, electrically disconnecting a direct current power supply from the reference voltage rails.

20. The method of claim 17, wherein acquiring the resulting signals comprises:

receiving second resulting signals from display electrodes and the plurality of sensor electrodes simultaneously.