Touch Electrode Auxiliary Structure for Noise Immunity
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Solution Overview
Problem
Self-capacitive touch devices face accuracy and sensitivity issues due to varying capacitance to ground caused by environmental factors and electromagnetic interference, leading to noise in signal detection and increased threshold values for touch signal determination.
Innovation Solution
The touch structure includes a matrix of touch electrodes and auxiliary electrodes driven with the same signal, where the driving circuit only reads the self-capacitance of the touch electrodes, excluding the noise component from the auxiliary electrodes to ground, ensuring that the capacitance change detected is purely from the finger to ground, thereby reducing noise and improving accuracy and sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If self-capacitive touch detection is used, then touch sensitivity is improved, but measurement precision deteriorates due to environmental noise affecting capacitance to ground
Solution Approach 1:
The patent divides the touch electrode into multiple segments (first touch electrode and second touch electrode) that are electrically connected but physically separated. This segmentation allows the system to distinguish between capacitance changes at different locations and reduce the impact of environmental noise on individual segments, thereby improving measurement precision while maintaining touch sensitivity.
Solution Approach 2:
The patent introduces an auxiliary electrode as an intermediary element between the touch electrode and ground. The auxiliary electrode is coupled to the drive circuit and used to compensate for environmental noise and capacitance variations. By using this intermediary, the system can isolate the true touch signal from environmental interference, improving both sensitivity and measurement precision.
2Ease of operation
If capacitance to ground is used for touch detection, then touch response is improved, but object-affected harmful factors increase due to electromagnetic interference from nearby circuit signals
Solution Approach 1:
The auxiliary electrode serves as a mediator that is specifically designed to counteract electromagnetic interference. It is coupled to the drive circuit and positioned to experience similar environmental noise conditions as the touch electrode. By processing the signal from the auxiliary electrode, the system can compensate for and eliminate harmful electromagnetic interference, allowing for responsive touch operation without the detrimental effects of EMI.
Solution Approach 2:
The system uses the auxiliary electrode to provide feedback information about environmental noise and capacitance variations to the drive circuit. This feedback mechanism allows the drive circuit to dynamically adjust its operation to compensate for electromagnetic interference, maintaining touch responsiveness while filtering out harmful factors from the detection signal.
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 the accuracy and sensitivity of touch detection by isolating the finger-to-ground capacitance from environmental noise, allowing for a lower threshold for touch signal detection and improved overall performance.
Implementation Method 1
a self-capacitance of the touch electrode changes as a result of parallel connection of a capacitance of the finger to the ground and a capacitance of the touch electrode to the ground
Implementation Method 2
electromagnetic interference from nearby circuit signals, etc., the value of the capacitance of the touch electrode to the ground constantly changes, forming noise in signals received by the drive circuit
Data Source
AI summary
A touch structure which is immune to variations in capacitance of a touch electrode to ground includes touch electrodestouch electrodes, auxiliary electrodes, and a driving circuit. The driving circuit drives the auxiliary electrodes with the same driving signal as the touch electrodes but does not read changes in capacitance of the auxiliary electrodes when determining touch events. A touch device using the touch structure and a method for driving the touch structure are also disclosed.