Double-Layer Touch Electrode Switching for Low-EMI Displays
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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 with a double-layered touch electrode structure, where second touch electrodes are selectively connected to a low-level voltage source during non-touch sensing periods to reduce EMI, and connected in parallel with first touch electrodes during touch sensing periods to enhance touch sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If a single-layer touch electrode structure is used, then the device complexity is low, but the electromagnetic interference radiation is significant
Solution Approach 1:
The touch electrode structure is divided into two separate layers: a first touch electrode layer and a second touch electrode layer. Each layer can be independently controlled and optimized, allowing the first layer to handle touch sensing while the second layer is configured to minimize EMI radiation, thus resolving the contradiction between reducing EMI and maintaining structural simplicity
Solution Approach 2:
A touch insulating layer is introduced as an intermediary between the first touch electrode and the second touch electrode. This insulating layer electrically isolates the two electrode layers while allowing them to work cooperatively, enabling EMI reduction through the second electrode layer without interfering with the touch sensing function of the first layer
2Object-generated harmful factors
If second touch electrodes are connected to first touch electrodes during non-touch sensing periods, then touch sensitivity is maintained, but electromagnetic interference radiation increases
Solution Approach 1:
The electrical connection state between the first and second touch electrode layers is made dynamic rather than static. During touch sensing periods, the layers are electrically connected to maintain high touch sensitivity. During non-touch sensing periods, they are electrically disconnected to reduce EMI radiation. This dynamic switching resolves the contradiction by adapting the connection state to the operational requirements
Solution Approach 2:
The touch driver circuit periodically switches the electrical connection between the first and second touch electrode layers based on the sensing phase. During capacitive sensing phases, the layers are connected; during non-sensing phases, they are disconnected. This periodic action allows the system to alternate between high sensitivity mode and low EMI mode, resolving the contradiction between these two opposing requirements
3Measurement precision
If a double-layered touch electrode structure is implemented, then touch sensitivity is improved, but the device complexity increases
Solution Approach 1:
The second touch electrode layer serves multiple functions: it acts as a shield to reduce EMI radiation, provides additional capacitive sensing capability to enhance touch sensitivity, and can be independently controlled through the touch driver circuit. By making the second layer multi-functional, the increased structural complexity is justified by the multiple benefits it provides, resolving the contradiction between complexity and performance improvement
Solution Approach 2:
The first and second touch electrode layers are merged into a unified touch sensing system that operates cooperatively. The touch driver circuit integrates control of both layers, and the touch insulating layer facilitates their coordinated operation. This merging allows the system to achieve enhanced touch sensitivity through combined capacitive sensing while managing the complexity through integrated control architecture
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 double-layered electrode structure effectively reduces EMI radiation and improves touch sensitivity and performance by managing electromagnetic interference and enhancing capacitive sensing capabilities.
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.