Capacitive Sensor CV Amplifier With Switched Feedback Capacitance
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Solution Overview
Problem
Conventional CV conversion amplifiers face challenges in securing high capacitance-to-voltage conversion gain and amplitude range while maintaining low power consumption and noise, as increased gain leads to decreased amplitude range and faulty operation due to shifted center voltage levels.
Innovation Solution
A capacitive sensor design incorporating multiple capacitances and operational amplifiers with switch-controlled charging mechanisms to periodically adjust capacitance values and charge potentials, ensuring a stable output voltage range with minimal power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the capacitance-to-voltage conversion gain is increased, then the noise performance is improved, but the amplitude range of the output voltage is considerably decreased
Solution Approach 1:
The patent applies dynamics by making the feedback capacitance value variable rather than fixed. The capacitance value is dynamically adjusted based on the input signal amplitude to maintain optimal noise performance across different operating conditions. This is achieved through a capacitance switching mechanism that selects appropriate feedback capacitance values according to the signal level, allowing the system to adapt its conversion gain dynamically.
Solution Approach 2:
The patent changes the parameter of feedback capacitance value to resolve the contradiction. By varying the feedback capacitance value between different predetermined values, the system can adjust the conversion gain to maintain low noise performance while preventing excessive center voltage level shifts that would limit the output amplitude range.
2Measurement precision
If the capacitance-to-voltage conversion gain is increased, then the noise performance is improved, but the center voltage level is shifted from the desired value causing faulty operation
Solution Approach 1:
The patent implements feedback by continuously monitoring the center voltage level of the operational amplifier output and using this information to adjust the feedback capacitance value. The center voltage level detection circuit provides feedback signal that controls the capacitance switching, ensuring that the conversion gain is optimized while maintaining the center voltage level within the desired range to prevent faulty operation.
Solution Approach 2:
The system performs self-adjustment by automatically modifying its own feedback capacitance value based on the detected center voltage level. The capacitance switching mechanism is controlled by the system itself through the center voltage level detection, allowing the amplifier to self-optimize its performance without external intervention.
3Length of moving object
If a capacitance for adjusting the in-phase potential is added, then the amplitude range is secured, but the consumption current is more greatly increased
Solution Approach 1:
The patent applies dynamics by switching between different feedback capacitance values only when necessary, rather than continuously adjusting or adding large compensation capacitances. The capacitance switching mechanism activates only when center voltage level adjustment is needed, minimizing the impact on consumption current while still securing the amplitude range.
Solution Approach 2:
The patent implements periodic action through the center voltage level detection and capacitance switching mechanism that operates at specific intervals or conditions rather than continuously. The capacitance value is adjusted periodically or event-driven based on center voltage level deviations, reducing the continuous power consumption associated with constant adjustment mechanisms.
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 effectively secures a high capacitance-to-voltage conversion gain and amplitude range with reduced power consumption and noise, enabling wide tolerance of input signals in capacitive sensors.
Implementation Method 1
a first operational amplifier and a second operational amplifier; converts a capacitance value into a voltage signal
Implementation Method 2
a first electrode of the first capacitance is connected to a first electrode of the second capacitance, and a first signal is supplied to the first electrodes
Implementation Method 3
a first electrode and a second electrode of the third capacitance are connected to the inverting input terminal and an output of the first operational amplifier, respectively, directly or through a switch
Implementation Method 4
The first electrode of the third capacitance is connected to a first charge potential through the first switch, and the second electrode of the third capacitance is connected to a second charge potential through the second switch
Data Source
AI summary
A CV conversion amplifier is provided that can secure a sufficient capacitance-to-voltage conversion gain and a sufficient amplitude range of an output voltage with a small consumption current. A capacitive sensor using the CV conversion amplifier is provided with low electric power, low noise, and a wide tolerance of input signals. The CV conversion amplifier accepts outputs, as inputs, from a first capacitance and a second capacitance whose capacitance is changed depending on a physical quantity and converts a capacitance value into a voltage.