Current Sensor with Split Feedback Coils for Noise Rejection
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Solution Overview
Problem
Current magnetic balance type current sensors have limited noise tolerance, making them inadequate for measuring both large and small currents accurately, and require improved noise resistance for various magnetic field measurements.
Innovation Solution
A current sensor configuration featuring a magnetic detecting device with two coils to cancel the measured magnetic field, a shunt resistor, and differential amplifiers to amplify signals, ensuring high noise tolerance and accurate current measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a magnetic balance type current sensor uses a closed loop system to cancel the magnetic field, then the linearity and temperature stability are improved, but the noise tolerance deteriorates
Solution Approach 1:
The feedback coil is divided into two separate coils arranged in the vertical direction. This segmentation allows each coil to be independently connected to different power supply potentials, enabling differential signal processing that improves noise rejection while maintaining the magnetic field cancellation function.
Solution Approach 2:
The patent transitions from a single-coil feedback mechanism to a two-coil vertical arrangement with differential connection. This dimensional change in the coil configuration enables the system to reject common-mode noise while maintaining the closed-loop magnetic field cancellation capability, thus improving noise tolerance without sacrificing measurement precision.
2Measurement precision
If the current sensor is designed for high accuracy measurement, then the measurement precision is improved, but the device complexity increases
Solution Approach 1:
The differential amplifier serves multiple functions: it amplifies the small signal from the magnetic detecting device, processes the differential output from the two feedback coils, and provides common-mode noise rejection. This multi-functionality reduces the need for additional dedicated noise filtering circuits, thereby maintaining measurement accuracy while limiting complexity increase.
Solution Approach 2:
The patent employs a closed-loop feedback system where the differential amplifier controls the feedback coils to cancel the magnetic field. This feedback mechanism inherently provides stability and accuracy while the differential connection of the coils simplifies the overall circuit architecture by integrating noise rejection into the feedback path itself.
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 proposed configuration enhances noise resistance and accuracy in measuring currents and magnetic fields, suitable for both large and small currents, and can be miniaturized for cost-effective and precise applications.
Implementation Method 1
a magnetic detecting device that is arranged in the vicinity of a conductor, to which a magnetic field to be measured induced by a current flowing through said conductor is applied, and that changes an electrical resistance in response to a change in the magnetic field to be measured
Implementation Method 2
two coils that generate a canceling magnetic field to cancel the magnetic field to be measured and that are arranged in the vicinity of the magnetic detecting device
Data Source
AI summary
The current sensor comprises: a magnetic detecting device that is arranged in the vicinity of a conductor, to which a magnetic field to be measured induced by a current flowing through the conductor is applied, and that changes an electrical resistance in response to a change in the magnetic field to be measured; two coils that generate a canceling magnetic field to cancel the magnetic field to be measured and that are arranged in the vicinity of the magnetic detecting device; a shunt resistor, that is connected in series between the two coils, for detecting a current flowing through the coils; a first differential amplifier that amplifies the output signal of the magnetic detecting device and that supplies the current to induce the canceling magnetic field to the coils; and a second differential amplifier that amplifies the voltage across the shunt resistor and that outputs a measured voltage proportional to the current flowing through the conductor.