Capacitive Voltage Derivative Circuit for Wide-Frequency Measurement
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Solution Overview
Problem
Existing derivative measurement circuits face limitations such as inadequate frequency range adaptation, complexity due to the need for operational amplifiers and microprocessors, and long processing times, particularly when dealing with rapid changes in voltage derivatives.
Innovation Solution
A derivative measurement circuit utilizing capacitive elements and a control circuit that implements successive cycles of clock signals to memorize and compare voltages across capacitive elements, eliminating the need for operational amplifiers and microprocessors, and enabling efficient measurement of voltage derivatives across wide frequency ranges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If an operational amplifier is used as a voltage differentiator, then the derivative of voltage can be measured, but the circuit is not adapted for wide frequency ranges and requires an operational amplifier with bandwidth greater than the input signal frequency range
Solution Approach 1:
The patent divides the derivative measurement function into multiple discrete capacitive elements (C1, C2, C3) that are selectively connected to the differential amplifier inputs through switches. Each capacitive element can be independently controlled to store voltage at different time instants, allowing the circuit to handle wide frequency ranges by segmenting the measurement function across multiple components rather than relying on a single operational amplifier with excessive bandwidth.
Solution Approach 2:
The circuit performs preliminary action by pre-storing voltage values on capacitive elements at specific time instants before the actual derivative calculation. The switches capture and hold voltage samples on capacitors C1, C2, C3 at different times (t, t-τ1, t-τ2), preparing the data in advance so that when the derivative calculation is needed, all required voltage samples are already available and stored, enabling rapid response without requiring the operational amplifier to process wide frequency ranges simultaneously.
2Measurement precision
If an ADC and microprocessor are used to calculate the derivative, then the derivative can be computed, but the device complexity increases and the processing time becomes too long for rapid countermeasures
Solution Approach 1:
The patent replaces the computational approach (ADC + microprocessor) with an analog electrical approach. Instead of digitizing voltages and performing computational derivative calculations, the circuit directly computes the derivative in the analog domain using a differential amplifier that subtracts pre-stored voltage samples. This substitution of mechanical/computational systems with electrical analog systems eliminates conversion and computing delays, providing rapid derivative measurement without sacrificing precision.
Solution Approach 2:
The circuit performs preliminary action by pre-storing voltage samples on capacitive elements before the derivative calculation is needed. The switches capture voltage values at specific past instants (t-τ1, t-τ2) and hold them on capacitors, so when the derivative is required, all necessary voltage data is already prepared and stored. This eliminates the need for real-time ADC conversion and computational processing, enabling instantaneous analog derivative calculation.
3Productivity
If multiple capacitive elements and switches are used to store and compare voltages, then the processing time is reduced and frequency range is expanded, but the device complexity increases
Solution Approach 1:
The patent segments the voltage storage function across multiple capacitive elements (C1, C2, C3) rather than using a single storage element. Each capacitor is dedicated to storing a voltage sample from a specific past instant, and the differential amplifier selectively compares these segmented storage units. This segmentation enables parallel preparation of multiple voltage samples, increasing processing speed and frequency response while distributing the complexity across identical, standardized components that can be easily integrated.
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 provides a compact and efficient method for measuring voltage derivatives, reducing processing time and eliminating the need for complex components, thereby overcoming the limitations of existing circuits.
Implementation Method 1
M capacitive elements, M being 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
AI summary
The present description concerns a derivative measurement circuit. The circuit implements successive cycles, each corresponding to a succession of first, second, and third periods of a clock signal. At each first period, an input voltage is memorized on a first capacitive element and the circuit delivers a voltage indicating a difference between a voltage on a second capacitive element and a voltage on a third capacitive element. At each second period, the input voltage is memorized on the second capacitive element and the circuit delivers a voltage indicating a difference between a voltage on the first capacitive element and the voltage on the third capacitive element. At each third period, the input voltage is memorized on the third capacitive element and the circuit delivers a voltage indicating a difference between the voltage on the second capacitive element and the voltage on the first capacitive element.