Capacitive Touch Frequency Sensing for Interference-Resistant Detection
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Solution Overview
Problem
Capacitive touch devices are prone to malfunction due to weak capacitance variation, which is affected by external factors like temperature, humidity, and electromagnetic interference, leading to inconsistent responses and sensitivity issues during manufacturing.
Innovation Solution
A capacitive touch sensing circuit comprising a touch capacitor, a frequency detection unit, a reference frequency generation unit, a calculation unit, and a determination unit, which detects and calculates the difference in output frequency to determine touch events with enhanced sensitivity and anti-interference capabilities by using a switching capacitor network and a charging/discharging circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional capacitive touch sensing is used, then the device structure remains simple, but the sensitivity is insufficient and the device is prone to malfunction due to weak capacitance variation
Solution Approach 1:
The patent replaces direct capacitance measurement with a frequency-based detection system. The touch capacitor is converted into an oscillating circuit where capacitance changes manifest as frequency changes, which are then measured by frequency detection units rather than direct capacitance sensing. This substitution enables higher sensitivity while maintaining manageable system complexity.
Solution Approach 2:
The patent transforms the measurement parameter from direct capacitance value to frequency variation. By converting the touch capacitor into an oscillating circuit, the system measures frequency changes (which are more easily detectable and less susceptible to noise) rather than directly measuring the weak capacitance variation, thereby improving sensitivity without proportionally increasing complexity.
2Reliability
If conventional touch sensing is used, then the manufacturing process is straightforward, but process drift causes sensitivity issues and requires careful testing and tuning
Solution Approach 1:
The patent implements a feedback mechanism where the actual frequency from the touch capacitor is continuously compared with a reference frequency. The determination unit uses this feedback to dynamically adjust and determine touch events, compensating for process drift and environmental variations. This feedback loop ensures consistent performance without requiring extensive manual testing and tuning during manufacturing.
Solution Approach 2:
The patent introduces a reference frequency as an intermediary element that mediates between the touch capacitor output and the determination logic. This reference frequency serves as a stable comparison point that compensates for manufacturing variations and environmental factors, enabling reliable touch detection without extensive calibration during the manufacturing process.
3Object-affected harmful factors
If conventional capacitive touch sensing is used, then the device responds to touch, but external factors like temperature, humidity, and electromagnetic interference cause inconsistent responses
Solution Approach 1:
The continuous frequency measurement and comparison with reference frequency creates a feedback mechanism that compensates for environmental variations. Temperature, humidity, and electromagnetic interference that cause drift in the touch capacitor characteristics are counteracted by the dynamic comparison process, maintaining detection accuracy despite changing environmental conditions.
Solution Approach 2:
The patent converts the harmful effect of environmental factors into a useful signal. Instead of trying to completely isolate the touch capacitor from environmental influences, the system uses frequency modulation to encode touch information in a way that environmental variations affect both the reference and measured frequencies similarly, allowing the differential comparison to extract the true touch signal while rejecting environmental noise.
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 significantly enhances the sensitivity and reliability of touch sensing by magnifying the detection of touch events, reducing the impact of environmental factors and process drift, resulting in improved user interaction and reduced manufacturing complexities.
Implementation Method 1
a touch capacitor, for being touched; a touch capacitor frequency detection unit, coupled to the touch capacitor, for detecting an output frequency from the touch capacitor
Data Source
AI summary
A touch sensing circuit is provided. The touch sensing circuit includes: a touch capacitor, for being touched; a touch capacitor frequency detection unit, coupled to the touch capacitor, for detecting an output frequency from the touch capacitor; a reference frequency generation unit, for generating a reference frequency; a calculation unit, coupled to the touch capacitor frequency detection unit and the reference frequency generation unit, for calculating the variation of the difference between the output frequency from the touch capacitor and the reference frequency; and a determination unit, coupled to the calculation unit, for determining whether the touch capacitor is being touched based on whether the variation of the difference is greater than a criterion value.