Touch Panel Noise Filters for False Touch Reduction
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Solution Overview
Problem
Capacitive touch panels are prone to false touch detection due to external electromagnetic noise, which degrades sensing accuracy.
Innovation Solution
A touch panel driving device with noise filters having RC circuits with same resistance and capacitance values for each reception signal line, allowing for filtering operations with consistent characteristics, and switchable resistors and capacitors based on noise levels or scanning timing to optimize filtering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a filter (e.g., low pass filter) is introduced in the detection signal path to cut off high frequency external noise, then false touch detection is reduced, but the performance in detecting capacitance changes is degraded
Solution Approach 1:
The patent divides the reception signal lines into multiple groups and applies different filtering characteristics to each group. Specifically, it introduces noise filters with different cutoff frequencies for different reception signal lines, allowing optimized noise reduction for each line without uniformly degrading all capacitance detection performance.
Solution Approach 2:
The patent applies different filtering characteristics to different reception signal lines based on their specific noise characteristics and detection requirements. Each reception signal line receives a tailored filter configuration that balances noise rejection and signal fidelity for that particular line.
2Reliability
If noise filters with different filtering characteristics are applied to different reception signal lines, then noise reduction effectiveness is improved, but device complexity increases
Solution Approach 1:
The patent changes the filtering parameters (cutoff frequency, filter type) based on the characteristics of each reception signal line. By adjusting these parameters dynamically or statically during design, the system achieves optimized noise reduction while managing complexity through parameterization rather than completely different filter architectures.
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 configuration effectively reduces external noise interference, maintaining high sensing accuracy and minimizing performance deterioration from filtering, even in noisy environments.
Implementation Method 1
it is considered to have a filter (e.g., a low pass filter (LPF)) in a detection signal path and cut off a high frequency external noise component
Implementation Method 2
Each of the noise filters may include resistors having the same resistance values and capacitive elements having the same capacitance values. The noise filters have the same filter characteristics by, e.g., each filter having an RC (resistor and capacitor) circuit as an LPF with elements of the same values.
Data Source
AI summary
A touch panel driving device is provided for sequentially performing a scanning of selecting a pair of transmission signal lines from N number of transmission signal lines and a pair of reception signal lines from M number of reception signal lines. The touch panel driving device includes a reception circuit for respectively receiving, from the pair of reception signal lines, reception signals whose waveforms are changed due to a capacitance change caused by a touch operation and for generating a detection value for detecting the touch operation by comparing the received reception signals, and a plurality of noise filters provided in signal paths from the M number of reception signal lines to the reception circuit for performing a filtering operation of the same filtering characteristics on each of the reception signals supplied to the reception circuit from the pair of reception signal lines.