Minute Impedance Variation Detection for Touch Panels
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Solution Overview
Problem
Existing touch panels, particularly those with dual-layer ITO structures, face issues such as short circuits and reduced accuracy due to narrow layer gaps, and capacitive touch panels are affected by human body and earth electric fields, making it difficult to manufacture large-sized panels with high accuracy and stability.
Innovation Solution
A minute impedance variation detection device using a differential amplifier with impedances and capacitors connected in a specific configuration to amplify touch signals differentially, effectively reducing noise interference and enabling detection of minute variations, suitable for ITO electrodes with larger resistance values and large-sized touch panels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If ITO electrodes with smaller resistance value are used to improve accuracy and stability, then measurement precision is improved, but manufacturing cost increases and ease of manufacture deteriorates
Solution Approach 1:
The patent changes the detection parameter from direct voltage measurement to impedance variation measurement. By using a differential amplifier to detect impedance changes caused by touch, the system achieves high measurement precision without requiring low-resistance ITO electrodes, thus resolving the contradiction between detection accuracy and manufacturing ease
Solution Approach 2:
The patent replaces the conventional voltage-based detection mechanism with an impedance-based detection mechanism. This substitution allows the use of standard ITO electrodes while achieving high detection accuracy through the differential amplifier circuit that measures impedance variations rather than relying on low-resistance materials
2Reliability
If dual-layer ITO structure is used to improve touch detection capability, then sensing performance is improved, but short circuit risk increases due to narrow layer gap
Solution Approach 1:
The patent introduces an intermediary measurement approach by using a differential amplifier to detect impedance variations. Instead of directly measuring voltage across the narrow gap between ITO layers (which risks short circuit), the system measures impedance changes through a safe measurement path, eliminating the harmful short circuit effect while maintaining touch detection capability
Solution Approach 2:
The patent substitutes the direct electrical contact measurement method with an impedance-based measurement method. By measuring impedance variations through the differential amplifier rather than directly across the ITO layer gap, the system maintains sensing performance while avoiding the short circuit hazard inherent in dual-layer structures
3Speed
If capacitive touch panel is used to improve response speed, then speed is improved, but noise interference from human body and earth electric fields increases
Solution Approach 1:
The patent converts the harmful noise effect into a useful detection mechanism. By using a differential amplifier to detect impedance variations, the system can distinguish between noise signals and actual touch signals. The noise from human body and earth electric fields becomes part of the background impedance that the differential measurement can filter out, transforming the harmful interference into a manageable parameter
Solution Approach 2:
The patent implements a feedback mechanism through the differential amplifier that continuously monitors impedance variations. The amplifier compares the impedance at different points and provides feedback to distinguish actual touch signals from noise. This feedback approach maintains the fast response speed of capacitive touch panels while effectively filtering out noise from human body and earth electric fields
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 solution enhances sensitivity and accuracy by eliminating noise interference and allowing for the detection of minute impedance variations, making it suitable for large-sized touch panels with ITO electrodes of higher resistance values.
Implementation Method 1
the differential amplifier is based on the input signal and the touch signal to amplify differentially the touch signal and output the differentially amplified touch signal
Implementation Method 2
the first capacitor has a capacitance value close to that of the first parasitic capacitor and second parasitic capacitor connected in parallel
Data Source
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AI summary
A minute impedance variation detection device (1) includes a differential amplifier (11), first and second impedances (12, 13), a sensing electrode (15) and a signal source (16). The differential amplifier (11) has first and second input ends (111, 112) and an output end (113). The first impedance (12) is connected to the first input end (111). The second impedance (13) is connected to the second input end (112). The sensing electrode (15) is connected to the second input end (112) for sensing a touch and thus receiving a touch signal. The signal source (16) is connected to the first impedance (12) and the second impedance (13) for providing an input signal inputted to the first impedance (12) and the second impedance (13). The first impedance (12) has an impedance value close to that of the second impedance (13). The differential amplifier (11) is based on the input signal and the touch signal to differentially amplify the touch signal.