Dual-Layer Touch Electrode Switching for Low-EMI Sensing
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Solution Overview
Problem
Existing touch sensing modules in display devices suffer from significant electromagnetic interference (EMI) radiation, which is particularly problematic in electronic devices with strict EMI radiation restrictions, such as vehicles and wearable devices.
Innovation Solution
A touch sensing module design featuring first and second touch electrodes arranged in a double layer configuration, with the second electrodes selectively connected to a low-level voltage source during non-touch sensing periods to reduce EMI, and connected in parallel with first electrodes during touch sensing to enhance touch sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single layer of touch electrodes is used, then the device structure is simple, but electromagnetic interference radiation is significant
Solution Approach 1:
The touch electrode system is segmented into two separate layers: first touch electrodes (front layer) and second touch electrodes (rear layer). This segmentation allows the EMI generated by the driving electrodes to be contained and shielded by the corresponding second electrodes in the rear layer, thereby reducing external EMI radiation while maintaining touch sensing functionality.
Solution Approach 2:
The second touch electrodes are positioned directly beneath the first touch electrodes, creating a nested configuration where the rear layer electrodes are embedded within the spatial envelope of the front layer electrodes. This nested structure provides effective EMI shielding while minimizing additional device thickness.
2Object-generated harmful factors
If second touch electrodes are connected to low-level voltage source during non-touch period, then EMI radiation is reduced, but device operation complexity increases
Solution Approach 1:
The connection state of the second touch electrodes is dynamically changed based on touch detection mode: during non-touch periods, second electrodes are connected to low-level voltage source for EMI reduction; during touch sensing periods, they are connected in parallel with first electrodes for enhanced sensitivity. This dynamic switching is controlled by mode selection signals.
Solution Approach 2:
The touch driver circuit periodically switches the connection state of second touch electrodes between two modes: EMI reduction mode (connected to low-level voltage) during non-touch periods and touch sensing mode (connected in parallel) during touch periods. This periodic switching optimizes both EMI performance and touch detection accuracy.
3Measurement precision
If second touch electrodes are connected in parallel with first electrodes during touch sensing, then touch sensitivity is improved, but EMI radiation increases
Solution Approach 1:
The connection configuration of second touch electrodes is dynamically adjusted based on operational requirements: during touch sensing periods, they are connected in parallel with first electrodes to enhance capacitance and improve touch sensitivity; during non-touch periods, they are connected to low-level voltage source to minimize EMI radiation.
Solution Approach 2:
The system periodically alternates between two operational states: touch sensing state where parallel connection improves sensitivity, and EMI reduction state where low-level voltage connection minimizes radiation. This periodic state transition allows the system to optimize for different performance requirements at different times.
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
The design effectively reduces EMI radiation and improves touch sensitivity by minimizing electromagnetic interference while maintaining accurate touch position detection.
Implementation Method 1
a touch driver circuit that detects a touch position according to a change in the capacitance between the touch electrodes
Data Source
AI summary
A touch sensing module includes: first driving electrodes arranged in parallel; first sensing electrodes intersecting the first driving electrodes; second driving electrodes on a rear side of the first driving electrode with a touch insulating layer therebetween such that they are associated with the first driving electrodes, respectively; second sensing electrodes on a rear side of the first sensing electrodes with the touch insulating layer therebetween such that they are associated with the first sensing electrodes, respectively; driving switching circuits electrically connecting the second driving electrodes to the first driving electrodes, respectively, or to a low-level voltage source; and a touch driver circuit configured to supply touch driving signals to the first driving electrodes and to detect touch sensing signals through the first sensing electrodes to detect touch position coordinates.