Capacitance Detection Circuit With Linear Integrator Readout
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Solution Overview
Problem
Existing circuit arrangements for detecting capacitance and changes in capacitance, such as those used in vehicle closing elements, face complexity in implementing constant current sources and non-linear signal voltage progression over time, which complicates reliable detection of operating events.
Innovation Solution
A circuit arrangement utilizing a monostable multivibrator with an integrator and operational amplifier to generate a signal voltage that changes linearly with time, allowing for direct control of signal voltage levels and characteristic curves, eliminating the need for switching elements and constant current sources, and enabling precise detection of capacitance changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a constant current source and switching element are used to convert the monostable multivibrator output signal into a signal voltage, then the capacitance detection can be achieved, but the circuit complexity increases
Solution Approach 1:
The patent removes the constant current source and switching element from the circuit, extracting only the essential capacitive integration function. The monostable multivibrator output directly charges/discharges the integrator capacitor, eliminating unnecessary components while preserving capacitance detection capability.
Solution Approach 2:
The integrator circuit serves multiple functions: it converts the monostable multivibrator's time-based output into a voltage signal, provides linear signal progression, and enables capacitance detection without requiring separate constant current source circuitry. This multi-functionality reduces overall circuit complexity.
2Device complexity
If an RC low-pass filter is used to convert the monostable multvibrator output signal, then the circuit is simpler, but the signal voltage exhibits non-linear progression over time reducing detection reliability
Solution Approach 1:
The patent changes the fundamental operating parameter of the conversion circuit from exponential charging (RC filter) to linear charging (current integrator). By configuring the integrator with appropriate feedback components, the circuit produces a linearly progressing signal voltage that reliably reflects capacitance changes throughout the entire measurement range.
Solution Approach 2:
The patent replaces the passive RC filtering mechanism with an active integrator circuit that uses operational amplifiers to enforce linear signal progression. This substitution transforms the signal conversion process from a passive, non-linear physical process to an active, linearly controlled electrical process.
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 simplifies the detection of capacitance and capacitance changes, providing a reliable and efficient means to identify operating events for vehicle closing elements, with adjustable sensitivity and response thresholds, enhancing the accuracy and adaptability of the detection process.
Implementation Method 1
an integrator with an operational amplifier to convert an output signal generated at the output of the monostable multivibrator into a signal voltage, the waveform of which is proportional to the duration of the output signal
Implementation Method 2
an output signal is generated at the output of the monostable multivibrator, the duration of which depends on the capacitance of the capacitive component
Data Source
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AI summary
The present invention relates in particular to a circuit arrangement for detecting the capacitance of a capacitive component and/or a change in the capacitance of a capacitive component, comprising, among other things, the following: - a monostable flip-flop (2) controllable by a control signal, having at least two inputs (2.1, 2.3) and one output (2.4), wherein a first input (2.1) of the flip-flop (2) is provided for the control signal and a second input (2.3) is connected to a capacitive component (3), and wherein, upon activation, an output signal (AS) is generated at the output (2.4), the duration of which depends on the capacitance of the capacitive component (3), - a conversion device connected to the output (2.4) of the monostable flip-flop (2) and configured and provided to convert a signal at the output (2.3) into a variable signal (AS).4) to convert the generated output signal (AS) into a signal voltage (Ss) whose course is proportional to the duration of the output signal (AS), and - an evaluation unit (5) which is connected to the conversion device to evaluate the signal voltage (Ss) and to generate at least one detection value from it which indicates the capacitance and/or a change in the capacitance of the capacitive component (3). According to the invention, the conversion device comprises an integrator (6) with an operational amplifier (60) and the integrator (4) is designed and connected between the output (2.4) The monostable multivibrator (2) and the evaluation unit (5) are connected such that an output signal (AS) of the monostable multivibrator (2) is applied to an amplifier input (602) of the operational amplifier (60) and results in a signal voltage (Ss) that changes linearly with time, the values that the signal voltage (Ss) can assume are directly determined by the output signal (AS). Furthermore, the level of the signal voltage (Ss) can be controlled and/or a characteristic curve for the signal voltage (Ss) can be changed via a switchable adjustment device (8) of the circuit arrangement.