Capacitive Touch Detecting Device Self-Calibration
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Solution Overview
Problem
Current capacitive touch detection methods face issues with high power consumption, large circuit area, high hardware cost, and noise interference, as they rely on fixed baseline capacitance values that can be inaccurate due to environmental changes.
Innovation Solution
A capacitive touch detecting device with self-calibration capabilities, utilizing a clock provider, sampler circuit, and detection-and-calibration circuit to dynamically adjust parameters such as charging current, parasitic capacitance, and noise thresholds, and employing pipeline sampling to reduce noise accumulation and improve signal-to-noise ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If fixed baseline capacitance value is used during initialization, then device complexity is reduced, but measurement precision deteriorates due to environmental changes
Solution Approach 1:
The patent implements dynamic baseline capacitance calibration by periodically updating the baseline value during operation. The system transitions from a static fixed baseline to a dynamic adaptive baseline that automatically adjusts to environmental changes, resolving the contradiction between device simplicity and measurement accuracy.
Solution Approach 2:
The patent introduces feedback mechanisms where the system continuously monitors touch pad capacitance and compares it against the baseline. When deviations exceed thresholds, the system triggers recalibration to update the baseline, creating a closed-loop system that maintains precision without excessive complexity.
2Measurement precision
If tri-frequency continuous scanning or differential scanning is used, then measurement precision is improved by reducing noise interference, but device complexity increases
Solution Approach 1:
The patent employs periodic scanning at optimized frequencies rather than continuous multi-frequency scanning. By selecting specific scanning intervals and frequencies based on touch interaction patterns, the system achieves effective noise reduction while maintaining simpler circuit implementation compared to continuous tri-frequency scanning.
3Device complexity
If relaxation oscillator or voltage pulse method is used, then device complexity is reduced, but power consumption increases and measurement precision deteriorates
Solution Approach 1:
The patent uses periodic voltage pulses with optimized duty cycles and frequencies to charge and discharge the touch pad capacitor. By controlling the pulse width and frequency adaptively, the system reduces average power consumption compared to continuous relaxation oscillation while maintaining adequate measurement precision.
Solution Approach 2:
The patent applies partial charging/discharging cycles rather than full oscillation cycles. By using controlled voltage pulses that charge the capacitor to sufficient levels for detection without complete charging-discharging cycles, the system reduces power consumption while maintaining measurement accuracy.
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 device achieves low power consumption, reduced circuit area, enhanced noise resistance, and accurate touch detection by periodically calibrating parameters and adapting to environmental changes, thereby improving the signal-to-noise ratio and reducing hardware costs.
Implementation Method 1
charging a capacitor when a level of the clock signal is a first level, wherein the capacitor is electrically coupled to one of touch pads, a capacitance of the capacitor is a first capacitance when a touch event occurs
Data Source
AI summary
Disclosed is a capacitive touch detecting device including a sampler circuit and a detection-and-calibration circuit. The sampler circuit executes the following steps: charging a capacitor when the level of a clock signal is high, wherein the capacitor's capacitance is a first capacitance provided a touch event occurs and is a second capacitance provided the touch event doesn't occur, the first capacitance is greater than the second capacitance and related to a parasitic capacitance and a touch capacitance, and the second capacitance is unrelated to the touch capacitance; sampling a voltage determined by the capacitor during the level transition of the clock signal to generate a sample value; and discharging the capacitor when the level of the clock signal is low. The detection-and-calibration circuit determines whether the touch event occurs and whether at least one parameter needs to be updated according to the sample value and at least one parameter.