Fluxgate Current Sensor Circuit for Zero-Drift Wide-Range Measurement
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Solution Overview
Problem
Current sensors in electric vehicles face challenges in accurately measuring both high and low currents due to limitations in measurement range, sensitivity, and drift issues, which affect the precision of battery monitoring and safety in electric vehicles and charging systems.
Innovation Solution
A fluxgate current sensor with an excitation and detection circuit that uses a magnetic probe with an excitation iron core and coil, converting excitation currents into differential equivalent currents to eliminate zero drift and improve measurement accuracy by calculating average values, enabling precise measurement of a wide range of currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional fluxgate current sensors with single excited iron core are used, then the sensor structure is simple, but the current measurement range is limited and cannot accurately measure both large currents and small currents
Solution Approach 1:
The single excitation iron core is divided into two separate excitation iron cores (first and second excitation iron cores), each capable of independent saturation. This segmentation allows the sensor to measure both large and small currents accurately by selectively saturating appropriate cores based on current magnitude, thereby expanding the measurement range while maintaining structural simplicity.
2Ease of operation
If Hall current sensors are used in electric vehicles, then the installation is convenient, but the sensitivity and resolution are reduced and zero drift and temperature drift are relatively large
Solution Approach 1:
The patent replaces the Hall effect-based magnetic field detection with a fluxgate-based magnetic saturation detection mechanism. By using excitation coils to drive iron cores into saturation and detecting the resulting magnetic flux changes, the system achieves higher sensitivity and resolution while maintaining installation convenience, effectively substituting one detection principle with another superior one.
3Device complexity
If conventional current sensors are used, then the device is simple, but temperature drift and zero drift are small leading to reduced measurement accuracy
Solution Approach 1:
The patent implements a feedback mechanism where the detection coil monitors the magnetic flux in the excitation iron cores, and the system adjusts the excitation signals based on the detected saturation states. This feedback loop compensates for temperature drift and zero drift effects, maintaining measurement accuracy without significantly increasing device complexity.
4Volume of moving object
If single iron core fluxgate sensors are used, then the structure is compact, but the identification and measurement accuracy of small current is insufficient
Solution Approach 1:
By segmenting the single iron core into two separate excitation iron cores with different saturation characteristics, the system can selectively use appropriate cores for different current ranges. This segmentation enables accurate small current measurement while maintaining a compact overall sensor structure, as each core can be optimized for specific measurement 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 enhances current measurement accuracy by eliminating zero drift, allowing the sensor to detect currents from milliamps to thousands of amps with improved resolution and safety, particularly in electric vehicle battery packs and leakage current detection.
Implementation Method 1
the excitation coil is excited to generate alternating excitation currents ie and cause the excitation iron core to reach saturation alternately
Implementation Method 2
cause the excitation iron core to reach saturation alternately
Implementation Method 3
the excitation iron core is used to carry magnetic flux generated by the to-be-measured primary currents
Data Source
AI summary
A fluxgate current sensor and a current measurement method, wherein the fluxgate current sensor includes a magnetic probe and an excitation and detection circuit, and the magnetic probe includes an excitation iron core and an excitation coil, the excitation coil is connected to the excitation and detection circuit, the excitation and detection circuit is used to output alternating excitation voltages to the excitation coil, and the excitation coil is excited to generate alternating excitation currents and cause the excitation iron core to reach saturation alternately; the excitation and detection circuit is further configured to convert the excitation currents flowing through the excitation coil, into equivalent differences of two currents, so as to calculate average values of the excitation currents flowing through the excitation coil via differential equivalent currents, thereby calculating to-be-measured primary currents by the average values of the excitation currents.