Tunable Baseline Compensation for Touchscreen Controllers
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Solution Overview
Problem
Capacitive touch systems face challenges in accurately detecting conductive objects, especially in the presence of conductive liquids, due to interference from panel capacitance and water, which affects the reliability of touch sensing and gesture recognition.
Innovation Solution
A capacitance sensing circuit that utilizes mutual capacitances to compensate for panel capacitance and mitigate the effects of water, by coupling different groups of mutual capacitances to various voltages and using a compensation circuit to generate signals that help distinguish self capacitance from conductive objects, thereby improving the accuracy of touch detection and gesture recognition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If capacitance sensing is used to detect conductive objects, then touch detection capability is provided, but panel capacitance and water interference reduce measurement precision
Solution Approach 1:
The patent segments the capacitance measurement into two distinct components: self-capacitance measurement and mutual-capacitance measurement. By separately measuring these components and using mutual-capacitance to compensate for panel capacitance effects, the system isolates the harmful panel capacitance interference from the useful touch detection signal, thereby improving measurement precision in the presence of water and panel capacitance.
2Reliability
If mutual capacitance compensation is implemented, then water rejection capability is improved, but device complexity increases
Solution Approach 1:
The patent merges the self-capacitance sensing function and mutual-capacitance compensation function into a unified sensing system. By combining these two measurement modes and processing their outputs together, the system achieves water rejection capability without requiring completely separate hardware systems, thus limiting the increase in device complexity while improving reliability.
3Measurement precision
If multiple compensation capacitances are coupled to self capacitance, then measurement precision is improved, but conversion circuit complexity increases
Solution Approach 1:
The patent employs dynamic switching of compensation capacitances based on the measured self-capacitance values. The system selectively couples different compensation capacitances (first, second, third compensation capacitances) to the self-capacitance depending on the operating conditions and measured ranges. This dynamic approach allows the conversion circuit to maintain high measurement precision across different operating points without requiring all compensation capacitances to be simultaneously connected, thereby managing circuit complexity.
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
Enhances the reliability and accuracy of touch detection and gesture recognition by effectively compensating for panel capacitance and water interference, allowing for precise identification of conductive objects on capacitive touch arrays.
Implementation Method 1
The capacitive sense arrays work by measuring the capacitance of a capacitive sense element, and looking for a change in capacitance indicating a touch or presence of a conductive object.
Implementation Method 2
The electrical circuit converts the capacitances of the capacitive sense elements into digital values.
Implementation Method 3
A capacitance sensing circuit that utilizes mutual capacitances to compensate for panel capacitance and mitigate the effects of water
Data Source
AI summary
A method for compensating for panel capacitance the associated current is proposed, wherein the mutual capacitances of a capacitance sensing array are selectively coupled to drive voltages and to a self capacitance under test.