Modulating a reference voltage to perform capacitive sensing

Patent metadata

Field	Value
Publication number	US-2016196803-A1
Application number	US-201514788735-A
Country	US
Kind code	A1
Filing date	Jun 30, 2015
Priority date	Jan 5, 2015
Publication date	Jul 7, 2016
Grant date	—

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.

First claim

We claim:

1 . An input device, comprising:
a plurality of display electrodes; a plurality of sensor electrodes; and a processing system, comprising:
a reference voltage modulator configured to modulate the reference voltage rails during a first time period, wherein the processing system is configured to:
update a display using the display electrodes and the reference voltage rails of the processing system 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 first time period, and
acquire resulting signals from the plurality of sensor electrodes during the first time period.

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

3 . The input device of claim 1 , further comprising:
source drivers coupled to a plurality of sensor electrodes, wherein the source drivers are configured to drive a capacitive sensing signal onto the sensor electrodes for capacitive sensing, wherein the capacitive sensing signal is derived from the modulated reference voltage rails.

4 . The input device of claim 3 , wherein the source sensor electrodes are guarded from at least one interfering signal when being driven by the capacitive sensing signal derived from the modulated reference voltage rails.

5 . The input device of claim 3 , further comprising:
gate electrodes for updating the display; and source electrodes for updating the display, wherein, when driving the capacitive sensing signal onto the sensor electrodes, the gates electrodes are floated and the source electrodes are guarded.

6 . The input device of claim 1 , further comprising:
a power management controller configured to receive the unmodulated reference voltage rails when updating the display and convert the reference voltage rails into power voltages for powering display circuitry in a display panel comprising the display.

7 . The input device of claim 6 , 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 pixels.

8 . The input device of claim 1 , wherein the receiver is configured to simultaneously acquire resulting signals from both the display electrodes and sensing electrodes for performing capacitive sensing.

9 . The input device of claim 1 , further comprising:
a backlight, wherein the reference voltage modulator is configured to modulate the reference voltage rails while the backlight and the display are turned off.

10 . The input device of claim 1 , further comprising:
a display source; a display panel; and a high-speed data interface disposed on a same integrated circuit as the reference voltage modulator, the data interface is configured to communicate with the display source to receive display data for updating the display, wherein the high-speed 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.

11 . A processing system, comprising:
a reference voltage modulator configured to modulate reference voltage rails during a first time period; a receiver configured to, during the first time period, acquire resulting signals for a plurality of sensor electrodes; and a display module configured to update a display using a plurality of display electrodes and the reference voltage rails during a second time period that is non-overlapping with the first time period, wherein the reference voltage rails are held at unmodulated, DC voltages during the second time period.

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

13 . The processing system of claim 11 , further comprising:
a power management controller configured to receive the unmodulated reference voltage rails when updating the display and convert the reference voltage rails into power voltages for powering display circuitry in a display panel comprising the display.

14 . The processing system of claim 13 , 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 pixels.

15 . The processing system of claim 11 , wherein the receiver is configured to simultaneously acquire resulting signals from both the display electrodes and sensing electrodes for performing capacitive sensing.

16 . The processing system of claim 11 , wherein the processing system is configured to modulate the reference voltage rails while the backlight and the display are turned off.

17 . The processing system of claim 11 , further comprising:
a high-speed data interface disposed on a same integrated circuit as the reference voltage modulator, the data interface is configured to communicate with a display source to receive display data for updating a display, wherein the high-speed 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.

18 . A method, comprising:
updating pixels in a display of an input device using reference voltage rails and a plurality of display electrodes during a first time period, wherein the reference voltage rails are held at unmodulated, 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; and acquiring resulting signals from a plurality of sensor electrodes based on modulating the reference voltage rails.

19 . The method of claim 18 , 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.

20 . The method of claim 18 , further comprising:
before modulating the reference voltage rails, electrically disconnecting a DC power supply from the reference voltage rails.

21 . The method of claim 18 , wherein acquiring the resulting signals comprises:
receiving respective resulting signals from the display electrodes and sensor electrodes simultaneously, wherein the respective resulting signals are used for performing capacitive sensing.

Assignees

• Synaptics Inc

Inventors

• Reynolds Joseph Kurth
• Morein Stephen L

Classifications

• G09G2330/021

  Power management, e.g. power saving · CPC title

• G06F1/3228

  Monitoring task completion, e.g. by use of idle timers, stop commands or wait commands · CPC title

• G06F3/0418

  for error correction or compensation, e.g. based on parallax, calibration or alignment · CPC title

• G06F2203/04108

  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 title

• G06F2203/04101

  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 title