In-Cell Capacitive Sensing Low Power Modes

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Solution Overview

Problem

Capacitive sensing devices integrated with display devices face inefficiencies in power management due to dependency on display driver timing, leading to constrained touch functionality during display inactivity.

Innovation Solution

The integration of a processing system with a display driver module, transmitter module, and receiver module allows for independent operation of capacitive sensing, enabling the device to enter low power modes while still detecting touches and gestures, by synchronizing sensing data collection with the beginning of a display frame and switching between sensing modes based on object presence.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If capacitive sensing device depends on display driver timing, then sensing operation is synchronized with display updates, but touch functionality is constrained during display inactivity resulting in inefficient power management

Engineering Contradiction:

Improvesensing operation synchronizationVSAvoidpower management efficiency

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The patent segments the sensing operation into two distinct modes: a first sensing mode that operates during display updates and a second sensing mode that operates independently during display inactivity. This segmentation allows the sensing device to decouple from display driver timing constraints while maintaining reliable sensing functionality, enabling the display driver to enter sleep mode and improve power management efficiency

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent dynamically switches between different sensing modes based on display activity state. The sensing device transitions from the first sensing mode (dependent on display driver timing) to the second sensing mode (independent operation) when the display enters inactive state, and vice versa. This dynamic adaptation resolves the contradiction by maintaining reliability when needed while enabling power savings during inactivity

Inventive Principle:

Principle #15Dynamics

2Reliability

If display driver updates display continuously, then display content remains current, but power consumption increases preventing entry into low power modes

Engineering Contradiction:

Improvedisplay content currencyVSAvoiddisplay device power consumption

Core Design Contradiction:

ReliabilityVSUse of energy by stationary object

Solution Approach 1:

The patent implements periodic sensing operations at different rates based on display activity. During display updates, sensing occurs at a higher rate synchronized with display refresh. During display inactivity, sensing switches to a lower rate or different mode that maintains functionality while allowing the display driver to remain in sleep mode, thus reducing power consumption while preserving display content currency

Inventive Principle:

Principle #19Periodic action

3Use of energy by moving object

If capacitive sensing operates independently from display driver timing, then low power modes can be utilized more effectively, but synchronization of sensing data collection must be managed to reduce latency

Engineering Contradiction:

Improvelow power mode utilizationVSAvoidsensing data latency

Core Design Contradiction:

Use of energy by moving objectVSLoss of time

Solution Approach 1:

The patent synchronizes the transition to independent sensing mode with the beginning of display frames. By initiating sensing data collection at predetermined points (display frame boundaries), the system reduces potential latency that would occur with arbitrary timing transitions. This preliminary synchronization ensures that sensing operations are properly aligned with display refresh cycles, minimizing timing issues while maintaining the power savings from independent operation

Inventive Principle:

Principle #10Preliminary action

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This approach enhances power management efficiency by allowing the display driver to remain in sleep mode longer, reducing overall power consumption while maintaining the ability to sense touches and gestures in 2D mode, and optimizing sensing techniques based on the device's power state.

Implementation Method 1

transmitter circuitry configured to, while in an active sensing mode, drive transmitter signals onto a first plurality of sensor electrodes of the capacitive sensing device for capacitive sensing

Methodology Applied

Scientific EffectCapacitive sensing: Capacitance

Implementation Method 2

the receiver module is configured to receive resulting signals from a second plurality of sensor electrodes, the resulting signals comprising effects corresponding to the transmitter signals

Methodology Applied

Scientific EffectCapacitance detection: Capacitance

Data Source

PatentUS10025412B2In-cell low power modes

Publication Date: 2018.07.17 SYNAPTICS INC

AI summary

Embodiments described herein include a method and apparatus for capacitive sensing in input devices integrated with a display device. In one embodiment, a processing system for a display device comprising an integrated capacitive sensing device is provided that includes a display driver module, a transmitter module, and a receiver module. The display driver and transmitter modules are configured to operate in a display update mode and a sleep mode. The receiver module is configured to, while operating in a doze mode, communicate with and trigger the transmitter module to enter the active sensing mode while the display driver module remains in the sleep mode when presence of an object is detected based on the resulting signals.