Current Sensor Impedance Matching for Low-Distortion Measurement
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Solution Overview
Problem
Current sensors face issues with high power consumption and waveform distortion due to impedance mismatch, particularly when measuring high electric currents, as the resistance values of starting and terminating resistors need to match the characteristic impedance of the transmission line to suppress reflection.
Innovation Solution
A current sensor design that includes a magnetic core, a coil, a transmission line, a terminating resistor, and an impedance matching unit to adjust the impedance viewed from the terminating and starting ends of the transmission line to the characteristic impedance, especially in the attenuation band, reducing reflection and power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the resistance value of the starting resistor or terminating resistor is set to be equivalent to the characteristic impedance of the transmission line to suppress reflection, then waveform distortion is suppressed, but power consumption increases significantly
Solution Approach 1:
The patent applies local quality by making the impedance matching frequency-dependent. The matching unit adjusts the impedance to match the characteristic impedance of the transmission line only in the attenuation band where reflection causes waveform distortion, while maintaining a lower impedance in other frequency bands to reduce power consumption. This localized impedance adjustment resolves the contradiction by applying impedance matching only where necessary for signal quality.
Solution Approach 2:
The patent employs dynamics by using a matching unit that dynamically adjusts the impedance based on frequency. The impedance viewed from the terminating end or starting end of the transmission line is raised to the characteristic impedance specifically in the attenuation band, while remaining substantially unchanged outside this band. This dynamic impedance adjustment allows the system to suppress reflection only when needed, thereby reducing overall power consumption while maintaining signal quality in critical frequency ranges.
2Measurement precision
If a large electric current flows through the object to be measured, then measurement capability is improved, but power consumption in the current sensor increases notably
Solution Approach 1:
The patent applies local quality by restricting impedance matching to the attenuation band only. In this frequency range, the impedance is raised to match the transmission line characteristic impedance to suppress reflection and maintain measurement accuracy. Outside the attenuation band, the impedance remains lower, reducing power consumption. This selective approach allows accurate measurement of large currents while minimizing power consumption in non-critical frequency ranges.
Solution Approach 2:
The patent employs dynamics by making the impedance adjustment frequency-dependent through the matching unit. The impedance is dynamically raised to the characteristic impedance only in the attenuation band where measurement accuracy is compromised by reflection, while maintaining lower impedance in other bands. This dynamic behavior enables the sensor to maintain measurement precision for large currents without proportionally increasing power consumption across all frequency ranges.
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 suppresses waveform distortion and power consumption in the current sensor, allowing for accurate measurement of high-frequency electric currents without significant increases in power usage.
Implementation Method 1
a coil wound around the magnetic core... configured to detect electric current flowing through an object to be measured
Data Source
AI summary
Technology includes a current sensor that detects electric current flowing through an object. The current sensor includes a magnetic core through which the object is inserted, a coil wound around the magnetic core, a transmission line that transmits electric current supplied from the coil, a terminating resistor that converts electric current from a terminating end of the transmission line into voltage and outputs the voltage, and an impedance matching unit that implements impedance matching between the coil and the terminating resistor. The impedance matching unit raises, to a characteristic impedance of the transmission line, at least one of an impedance viewed from the terminating end of the transmission line toward the terminating resistor and an impedance viewed from a starting end of the transmission line toward the coil, in a band of frequency components involving amplitude attenuation among frequency components of the voltage output from the terminating resistor.