Capacitive Touch Input Device Noise Suppression
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Solution Overview
Problem
Current input devices are limited in accurately detecting touch contacts due to noise interference, which affects the reliability of touch detection and cannot effectively suppress false detection.
Innovation Solution
An input device comprising a selection circuit, a calibration resistor, a constant current source, an A/D converter, and a control unit that measures capacitance ratios to differentiate between noise and actual touch contacts by using a calibration resistor connected in parallel with the electrodes, allowing for noise suppression and accurate touch coordinate determination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If noise suppression methods are implemented in input devices, then detection accuracy is improved, but device complexity increases
Solution Approach 1:
The patent applies preliminary action by measuring capacitance values before actual touch detection to establish baseline data. The control unit stores multiple capacitance values measured at different times prior to touch detection, creating a reference profile that enables later differentiation between noise and actual touch events based on temporal patterns and capacitance changes.
Solution Approach 2:
The patent implements feedback by continuously monitoring capacitance changes and comparing them against stored baseline values. The control unit uses the difference between current capacitance measurements and previously stored values to determine whether a touch event occurred, adjusting detection thresholds dynamically based on the measured capacitance variations and their temporal relationships.
2Reliability
If multiple capacitance measurements are performed to distinguish noise from touch contacts, then detection reliability is improved, but measurement time increases
Solution Approach 1:
The patent performs preliminary capacitance measurements and stores the results in memory before actual touch detection begins. By pre-measuring and storing multiple capacitance values at different times, the system establishes a reference profile that enables rapid comparison during actual touch events, reducing the need for extensive real-time measurements.
Solution Approach 2:
The patent measures capacitance at multiple specific time points (excessive sampling) during the touch detection period to capture temporal patterns. The control unit stores these multiple values and compares them to distinguish between transient noise and sustained touch contacts, using the excess measurement data to improve reliability without requiring continuous measurement throughout the entire detection period.
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 enables accurate detection of touch contacts while suppressing noise interference, improving the reliability and accuracy of touch input devices by calculating capacitance ratios with a calibration resistor, effectively distinguishing between noise and actual touch events.
Implementation Method 1
an A/D converter connected to the selection circuit to measure capacitance of the plurality of electrodes
Data Source
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AI summary
The present invention provides for an input device (1) including a selection circuit (20) that is connected to a plurality of electrodes (30) provided on a capacitive touch panel (3) and selectively connects the plurality of electrodes (30), a calibration resistor (RCAL) connected to the selection circuit (20), a constant current source (21) for supplying constant current power to the plurality of electrodes (30) and the calibration resistor (RCAL), an A/D converter (22) connected to the selection circuit (20) to measure capacitance of the plurality of electrodes (30) and a measured value measured when the calibration resistor (RCAL) is connected, and a control unit (23) arranged for controlling the selection circuit (20) to make the A/D converter (22) measure the capacitance of one of the plurality of electrodes (30) and the measured value measured when the calibration resistor (RCAL) is connected, and determining a contact coordinate of a touch object on a touch panel (3) by calculating a ratio of the capacitance to the measured value.