Capacitance Detection Device Using Switched Array for Parasitic Noise
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Solution Overview
Problem
Existing capacitance detection devices face challenges in accurately determining the presence of a detection target due to variations in parasitic capacitance, requiring a large number of switch operations which increases determination time and reduces accuracy, and are susceptible to low-frequency noise and power supply fluctuations.
Innovation Solution
A capacitance detection device featuring a capacitor array with multiple parallel capacitors of different capacitances, a detection capacitor, and a control unit that adjusts the combined capacitance to determine the presence of a target by analyzing the intermediate potential and setting a determination threshold based on capacitance changes, independent of parasitic capacitance effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the number of switch operations is increased to improve determination accuracy, then measurement precision improves, but determination time increases and the system becomes more susceptible to low-frequency noise and power supply fluctuations
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing determination thresholds for different combined capacitance values before actual measurement. The control unit stores multiple threshold values corresponding to different capacitor array configurations, allowing the system to perform rapid comparison during measurement without requiring extensive real-time calculations or repeated switch operations, thus reducing determination time while maintaining accuracy
Solution Approach 2:
The patent implements dynamics by adaptively selecting the appropriate determination threshold based on the actual combined capacitance value. The control unit dynamically chooses the threshold that corresponds to the current capacitor array configuration, enabling the system to optimize its measurement process for each specific capacitance state rather than using a fixed threshold, thereby improving both speed and accuracy
2Measurement precision
If the number of switch operations is increased to improve determination accuracy, then measurement precision improves, but the system becomes more susceptible to low-frequency noise and power supply fluctuations
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing determination thresholds for different combined capacitance values before actual measurement. The control unit stores multiple threshold values corresponding to different capacitor array configurations, allowing the system to perform rapid comparison during measurement without requiring extensive real-time calculations or repeated switch operations, thus reducing determination time while maintaining accuracy
Solution Approach 2:
The patent implements dynamics by adaptively selecting the appropriate determination threshold based on the actual combined capacitance value. The control unit dynamically chooses the threshold that corresponds to the current capacitor array configuration, enabling the system to optimize its measurement process for each specific capacitance state rather than using a fixed threshold, thereby improving both speed and accuracy
3Measurement precision
If a sensitivity compensation capacitor is selectively connected in parallel with the detection capacitor to compensate for parasitic capacitance effects, then measurement precision improves, but device complexity increases
Solution Approach 1:
The patent applies another dimension by transitioning from a single-capacitor approach to a multi-capacitor array system. Instead of using one detection capacitor with variable parasitic effects, the system employs multiple capacitors (C1, C2, C3, C4) that can be selectively combined to create different combined capacitance values. This dimensional expansion allows the system to compensate for parasitic capacitance by selecting appropriate capacitor combinations rather than requiring additional compensation components
Solution Approach 2:
The patent implements parameter changes by varying the combined capacitance value through different switch configurations. The control unit selectively connects capacitors to achieve specific combined capacitance values (e.g., C1+C2, C1+C3, C2+C3, etc.), allowing the system to adapt its measurement parameters to compensate for parasitic effects and optimize determination accuracy for different measurement conditions
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
This solution allows for accurate detection of a target with reduced determination time, improved sensitivity, and reduced susceptibility to noise and parasitic capacitance variations, while simplifying the circuit configuration and lowering costs.
Implementation Method 1
an intermediate potential that is a potential of a capacitive voltage division of a power supply by the combined capacitance and a capacitance of the detection capacitor
Data Source
AI summary
A capacitance detection device includes: a capacitor array having parallel-connected capacitors having different capacitances, and whose combined capacitance is changed by selectively switching the capacitors; a detection capacitor connected in series to the capacitor array; a switching control unit selectively switching the capacitors; a detection unit detecting an intermediate potential that is a potential of a capacitive voltage division of a power supply; an acquisition unit acquiring, as a reference combined capacitance, any of the combined capacitances in a vicinity where a magnitude relationship between the intermediate potential and a predetermined reference potential is inverted; a determination unit determining whether or not a detection target is present; a capacitance change unit controlling the switching control unit to change the reference combined capacitance; and a setting unit setting the determination threshold based on a difference between the intermediate potentials in the reference combined capacitance and in the changed reference combined capacitance.