Touch Panel Impedance Matching for Uniform Detection Waveforms
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Solution Overview
Problem
Conventional capacitive touch panels with uneven RC loading distribution lead to excessive differences in detection voltage amplitudes, making it difficult for digital level discrimination in the analog-to-digital converter, especially when a human touches the panel.
Innovation Solution
Incorporating an impedance-matching network with independent RC circuits coupled to the output terminals of the capacitive touch panel, which shapes the detection signals to compensate for uneven RC loading, ensuring voltage amplitudes are uniform and facilitating digital level discrimination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fixed reference voltage is used in the analog-to-digital converter, then the converter can operate with a stable reference level, but the excessive differences in amplified detection voltage amplitudes make digital level discrimination difficult
Solution Approach 1:
The patent applies parameter changes by adjusting the resistance values in the RC circuits of the impedance-matching network to compensate for uneven RC loading distribution. This equalizes the detection voltage amplitudes across different output terminals, enabling effective digital level discrimination while maintaining a stable fixed reference voltage in the analog-to-digital converter.
2Power
If the voltage amplifier magnification is set based on the maximum detection voltage, then the maximum voltage can be properly amplified, but the minimum detection voltage becomes too small to facilitate digital level discrimination
Solution Approach 1:
The patent applies preliminary anti-action by using the impedance-matching network to pre-compensate for amplitude differences before the signals reach the voltage amplifier. This equalization occurs in advance, preventing the excessive amplitude differences that would otherwise make digital level discrimination difficult after amplification.
Solution Approach 2:
The impedance-matching network changes the amplitude parameters of detection voltages by using RC circuits with specifically designed resistance values. This equalizes the amplitudes of detection voltages from different output terminals before they are amplified, ensuring that both maximum and minimum voltages fall within the optimal range for digital level discrimination.
3Productivity
If the capacitive touch panel uses double-side driving mode, then the whole panel can be scanned effectively, but the original RC loading distribution becomes uneven causing excessive differences in detection voltage amplitudes
Solution Approach 1:
The patent applies local quality by designing RC circuits with different resistance values for different output terminals based on their specific positions in the panel. The impedance-matching network provides localized compensation for each output terminal's RC loading characteristics, equalizing the detection voltage amplitudes across all terminals while maintaining the double-side driving mode for comprehensive panel scanning.
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 impedance-matching network effectively improves the signal processing by making voltage amplitudes consistent, enhancing digital level discrimination and improving the overall performance of the capacitive touch detection system.
Implementation Method 1
the impedance-matching network is for performing a waveform shaping operation applied to the detection signals to compensate the effect caused by uneven RC loading distribution
Data Source
AI summary
An exemplary capacitive touch detection system includes a capacitive touch panel and a detection control circuit. The capacitive touch panel includes a plurality of input terminals and output terminals. The detection control circuit includes a scanning signal transmitting module electrically coupled to the input terminals and a detection signal receiving and waveform shaping module including a receiver and an impedance-matching network. The detection signal receiving and waveform shaping module is electrically coupled to the output terminals for receiving and processing a plurality of detection signals outputted from the respective output terminals and thereby producing a plurality of processed detection signals. The receiver is used for receiving the detection signals. The impedance-matching network is used for performing a waveform shaping operation applied to the detection signals to compensate an effect caused by uneven RC loading distribution in the capacitive touch panel and thereby producing the processed detection signals.