Capacitance-to-Voltage Converter With Overflow Cancellation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Capacitive touch sensors face an overflow issue when detecting pressure due to the large inductive capacitance generated by a user's touch, which prevents accurate conversion to a corresponding voltage value.
Innovation Solution
A capacitive pressure sensing circuit with a cancellation or suppression circuit is used to attenuate the inductive capacitance, preventing overflow and allowing for effective conversion of capacitance to voltage, comprising a converter, cancellation/suppression circuit, analog-to-digital converter, and digital signal processor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a capacitive touch sensor is used to detect pressure, then the sensor can detect touch events with lower cost and higher signal-noise ratio, but an overflow occurs when detecting pressure because the inductive capacitance becomes too large for correct conversion
Solution Approach 1:
The patent segments the capacitance measurement into two parts: a large capacitive component (Cx) that causes overflow and a small variable component (Cs) that contains the pressure information. By using a switched capacitor circuit to handle the large Cx separately and measuring only the remaining small Cs, the system avoids overflow while maintaining measurement accuracy. This segmentation allows the converter to process the signal in manageable portions.
Solution Approach 2:
The patent extracts and removes the large capacitive component (Cx) from the total capacitance signal before conversion. The switched capacitor circuit selectively discharges or bypasses the large Cx component, leaving only the small variable capacitance (Cs) to be converted by the capacitance-to-voltage converter. This extraction prevents the overflow issue while preserving the pressure-related signal.
2Device complexity
If the inductive capacitance is directly converted to voltage, then the conversion process is simple, but the large capacitance value causes overflow and prevents correct voltage output
Solution Approach 1:
The patent introduces a switched capacitor circuit as an intermediary component between the capacitive sensor and the capacitance-to-voltage converter. This intermediary selectively handles the large capacitive component by providing alternative discharge paths or bypass routes, allowing the small variable capacitance signal to pass through to the converter without being overwhelmed by the large Cx value. The intermediary protects the converter from overflow while maintaining signal integrity.
Solution Approach 2:
The patent employs dynamic switching mechanisms where capacitors are alternately connected and disconnected based on control signals. The switched capacitor circuit dynamically redirects the large capacitive current away from the conversion path during specific time periods, while allowing the small variable capacitance signal to be measured during other periods. This dynamic approach enables the system to handle large capacitance values without overflow.
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 prevents overflow and enables accurate conversion of inductive capacitance to a corresponding voltage signal, ensuring reliable pressure sensing without signal distortion.
Implementation Method 1
The converter receives a sensing signal provided by the pin, and thereby outputs an analog voltage signal
Implementation Method 2
The suppression circuit suppresses the sensing signal according to a predetermined parameter and provides the suppressed sensing signal to the converter
Data Source
AI summary
Disclosed is a capacitive pressure sensing circuit and a capacitance-to-voltage converter thereof. The pressure sensing circuit comprises a converter, a cancellation circuit and a signal processor. The cancellation circuit is connected between the converter and at least one capacitive pressure sensor. The cancellation circuit attenuates the inductive capacitance generated by the capacitive pressure sensor to prevent an overflow happening when the inductive capacitance received by the converter is too large, such that the converter can effectively output a voltage signal corresponding to the attenuated inductive capacitance.