Magnetic Balance Current Sensor Temperature Compensation
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Solution Overview
Problem
High-performance electric vehicles face measurement accuracy errors due to temperature characteristics differences between magnetoresistive effect elements and pinned resistive elements in magnetic balance type current sensors, especially when handling increased current values.
Innovation Solution
A magnetic balance type current sensor is designed with a pair of sensor elements, each comprising a magnetoresistive effect element and a pinned resistive element, along with a feedback coil, forming a bridge circuit for magnetic field detection. The sensor elements are positioned to have equal magnetic fields from the measured current, with one aligned forward and the other reverse to the magnetic field, and a magnetic shield is used to attenuate and enhance the magnetic fields, allowing for accurate current measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a magnetic balance type current sensor uses a magnetoresistive effect element and pinned resistive element to detect current, then the current measurement capability is provided, but measurement accuracy deteriorates due to temperature characteristics differences between the elements when handling increased current values
Solution Approach 1:
The current sensor is divided into a first current sensor and a second current sensor, each with separate magnetoresistive effect elements and pinned resistive elements. This segmentation allows independent temperature compensation for each sensor, improving overall measurement accuracy under temperature variation.
Solution Approach 2:
The patent applies temperature compensation by changing the resistance parameters of the pinned resistive elements based on temperature characteristics. By adjusting the resistance values to match the temperature dependence of the magnetoresistive effect elements, the bridge circuit maintains balance accuracy across temperature ranges, resolving the measurement stability issue.
2Productivity
If the current value to be handled increases, then the current measurement range is expanded, but measurement accuracy deteriorates due to temperature characteristics differences between elements
Solution Approach 1:
By segmenting the sensor into multiple current sensors handling different current ranges, each sensor operates within its optimal accuracy range. The first current sensor handles lower currents with high precision, while the second current sensor handles higher currents, collectively expanding the measurement range without sacrificing accuracy.
Solution Approach 2:
Temperature compensation through parameter adjustment of the pinned resistive elements ensures that measurement accuracy is maintained across different current values. The resistance parameters are optimized to compensate for temperature effects that become more pronounced at higher current levels.
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 configuration effectively cancels errors caused by temperature rises, enabling high-accuracy current measurement even with increased current values, with the sensor elements arranged symmetrically to minimize temperature-induced noise and maintain high linearity between feedback coil current and measured current.
Implementation Method 1
a magnetoresistive effect element, the resistance value of which changes due to application of an induction magnetic field from a measured current
Implementation Method 2
a feedback coil arranged in the vicinity of the magnetoresistive effect element to generate a cancel magnetic field canceling the induction magnetic field
Data Source
AI summary
A magnetic balance type current sensor measures a measured current which flows in a feedback coil when electrical conduction is provided by a voltage difference according to an induction magnetic field from the measured current and an equilibrium state is reached in which the induction magnetic field and a cancel magnetic field cancel each other. Sensor elements in a pair are arranged at positions with magnetic field from the measured current. The magnetization direction of the pinned magnetic layer in the magnetoresistive effect element of one sensor element is aligned in a forward direction with respect to the magnetic field formed by the measured current. The magnetization direction of the pinned magnetic layer in the magnetoresistive effect element of the other sensor element is aligned in a reverse direction with respect to the magnetic field formed by the measured current.