Capacitive Derivative Circuit for Wide-Frequency Voltage Sensing
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Solution Overview
Problem
Existing methods for measuring the derivative of a voltage, such as using operational amplifiers or analog-to-digital converters, are limited by bandwidth requirements, complexity, and slow response times, particularly when rapid changes in voltage need to be detected.
Innovation Solution
A circuit utilizing capacitive elements and control switches, operating in synchronized cycles, to measure the derivative of a voltage by storing and comparing voltages across multiple capacitors, allowing for rapid determination of voltage differences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If an operational amplifier is used to measure the derivative of a voltage, then the measurement can be obtained, but the solution is not suitable for wide frequency ranges and requires an operational amplifier with a bandwidth greater than the frequency range of the input signal
Solution Approach 1:
The patent segments the derivative measurement process into discrete time steps using multiple capacitive elements (first, second, third capacitive elements) that store voltage values at different instants. By dividing the measurement into sequential sampling phases controlled by clock signals, the circuit achieves wide frequency range adaptability without requiring high bandwidth operational amplifiers, thus resolving the contradiction between frequency range and device complexity.
Solution Approach 2:
The patent replaces the continuous analog operation of traditional operational amplifier-based derivative circuits with a discrete digital-like sampling approach using capacitive elements and switches. This substitution eliminates the bandwidth limitations of operational amplifiers while maintaining derivative measurement capability, thereby expanding the usable frequency range without increasing device complexity.
2Measurement precision
If an analog-to-digital converter and microprocessor are used to calculate the derivative, then the derivative can be calculated, but the solution is complex and the conversion time plus calculation time can be too long
Solution Approach 1:
The patent extracts the derivative calculation function from complex digital processing systems (ADC and microprocessor) and implements it directly in analog hardware using capacitive elements and switches. By taking out the calculation function and realizing it through voltage storage and subtraction operations on capacitive elements, the circuit achieves fast response times while significantly reducing device complexity.
Solution Approach 2:
The patent introduces capacitive elements as intermediary storage devices that hold voltage values at different time instants. These capacitive elements act as mediators between the input voltage signal and the derivative calculation process, enabling direct analog computation of the derivative without requiring ADC conversion and microprocessor calculation, thus reducing both complexity and response time.
3Measurement precision
If an analog-to-digital converter and microprocessor are used, then the derivative can be calculated, but the ADC conversion time plus the microprocessor calculation time can be too long
Solution Approach 1:
The patent implements continuous derivative measurement by maintaining capacitive elements in a perpetual sampling and comparison cycle driven by clock signals. The first capacitive element continuously stores the current voltage, while the second capacitive element stores a previous voltage value, enabling uninterrupted derivative calculation. This continuous operation eliminates the time delays associated with ADC conversion and microprocessor processing, achieving fast response times while maintaining measurement precision.
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
Enables efficient measurement of voltage derivatives across wide frequency ranges with reduced complexity and faster response times, enabling timely detection of rapid voltage changes.
Implementation Method 1
M capacitive elements, with M an integer greater than or equal to 1, each having a first terminal connected to a first input of the measurement circuit configured to receive a reference potential
Data Source
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AI summary
This description concerns a derivative measurement circuit (DER). The circuit comprises M capacitive elements (C1, C2, C3), each with a first terminal connected to a reference potential (GND). M switches (IT11, IT12, IT13) couple a second terminal of each of the M elements to a first voltage (V1). A first circuit (DIFF) provides an indication of a voltage difference between its inputs. Other switches (IT21, IT22, IT23, IT24, IT25, IT26) couple the second terminal of each of the M elements to the inputs of the first circuit.A control circuit (CTRL) implements successive cycles of M periods of a clock signal each, and controls the switches so that, at each period, one of the M capacitive elements stores the first voltage, a first input (208) of the first circuit receives a voltage stored on one of the M capacitive elements and a second input (210) of the first circuit receives a voltage representative of the first voltage.