Multi-phase self-capacitance scanning for touch sensors

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Solution Overview

Problem

Conventional self-capacitance sensing technologies face challenges in reducing electromagnetic emissions while maintaining high sensitivity and waterproofing, as they cannot simultaneously provide protection from electromagnetic interference and support high-sensitivity sensing.

Innovation Solution

The implementation of multi-phase self-capacitance (MPSC) scanning techniques, which involve concurrently sensing multiple sensor elements with opposite polarity excitation signals and using a multiplexor to couple sensor elements according to specific excitation patterns, allowing for simultaneous scanning of all elements and reducing electromagnetic emissions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-generated harmful factors

If conventional self-capacitance sensing with active shielding is used, then electromagnetic emissions are reduced, but sensitivity and waterproof sensing capability deteriorate

Engineering Contradiction:

Improveelectromagnetic emissionsVSAvoidsensitivity

Core Design Contradiction:

Object-generated harmful factorsVSMeasurement precision

Solution Approach 1:

The sensor array is divided into multiple independently controllable sensor elements that can be excited in different phases. By segmenting the excitation signals into multiple phases with opposite polarities, the system achieves both electromagnetic emission reduction through differential signaling and maintains high sensitivity by independently controlling each segment's excitation state

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The system changes the excitation signal parameters by applying opposite polarity voltages to different sensor elements in different phases. This parameter change enables differential measurement modes that reduce electromagnetic emissions while maintaining measurement precision through the contrasting signal states

Inventive Principle:

Principle #35Parameter changes

2Device complexity

If conventional single-phase scanning is used, then device complexity is low, but scanning time is long and sensitivity is reduced

Engineering Contradiction:

Improvescanning architecture complexityVSAvoidscanning time

Core Design Contradiction:

Device complexityVSLoss of time

Solution Approach 1:

The system implements multi-phase periodic scanning where sensor elements are excited in alternating phases with opposite polarities. This periodic action allows multiple sensor elements to be scanned concurrently in each phase cycle, dramatically reducing total scanning time while the regular phase structure keeps control logic relatively simple

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

Multiple sensor element scans are merged into concurrent operations within the same time frame by using different phase assignments. Instead of scanning elements sequentially, the system combines multiple scanning operations across different phases simultaneously, reducing overall scanning time without proportionally increasing hardware complexity

Inventive Principle:

Principle #5Merging (Combining)

3Measurement precision

If multi-phase excitation with opposite polarity signals is applied, then sensitivity and scanning speed are improved, but device complexity increases

Engineering Contradiction:

Improvesignal-to-noise ratioVSAvoidexcitation control complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

Instead of using traditional single-polarity excitation, the system inverts the approach by applying opposite polarity signals to different sensor elements in different phases. This inversion creates differential measurement modes that improve signal-to-noise ratio through common-mode rejection, while the systematic phase-based control keeps the increased complexity manageable

Inventive Principle:

Principle #13The other way round (Inversion)

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 sensitivity by decreasing scanning time or increasing signal-to-noise ratio, while minimizing electromagnetic emissions and eliminating the impact of mutual capacitances, thus providing effective touch-sensor performance.

Implementation Method 1

Capacitive sensing typically involves scanning operations that periodically measure changes in capacitance associated with the capacitive sensor elements to determine a presence, position, type, and/or movement of a conductive object

Methodology Applied

Scientific EffectCapacitance sensing: Capacitance

Data Source

PatentUS10310687B2Multi-phase self-capacitance scanning of sensors arrays

Publication Date: 2019.06.04 INFINEON TECHNOLOGIES AMERICAS CORP

AI summary

Techniques for multi-phase self-capacitance (MPSC) scanning of a sensor array are described herein. In an example embodiment, a device comprises a sensor logic coupled to a processing logic. The sensor logic is configured to concurrently sense multiple sensor elements of the sensor array in each of multiple scanning operations in order to obtain multiple measurements, where each measurement represents a collective charge of the multiple sensor elements accumulated during a corresponding scanning operation. The processing logic is configured to determine data values based on the obtained multiple measurements, where the data values respectively represent self-capacitances of the multiple sensor elements.