Fluxgate Transducer Switching Circuit for Low-Offset Current Sensing
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Solution Overview
Problem
Conventional fluxgate transducers for current measurement are costly, complex, and suffer from magnetic offset issues due to remanence and coercive magnetic fields, making them less compact and less suitable for safety-critical applications requiring high reliability and low offset errors.
Innovation Solution
A fluxgate transducer with a control circuit that includes a PWM module for precise control of excitation coil switching, multiple measurement channels for redundancy, and a test winding for diagnostic validation, along with a controlled demagnetization procedure to ensure a deterministic magnetic state, enhancing reliability and safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional fluxgate transducers use auto-oscillating circuit architecture based on H-bridge circuit, then the transducer can generate excitation current for saturation of magnetic core, but it becomes difficult to actively change saturation level or define specific start-up sequence (degauss procedure)
Solution Approach 1:
The patent implements dynamic control of the excitation coil drive circuit, allowing the saturation level to be actively changed by adjusting the excitation current parameters. The control circuit can define specific start-up sequences including degauss procedures, making the system adaptable to different operating conditions while maintaining manageable complexity through structured control logic.
2Measurement precision
If fluxgate transducer uses high sensitivity design, then measurement precision is improved, but offset error due to remanence and coercive magnetic field becomes more significant
Solution Approach 1:
The patent implements a degauss procedure as a preliminary action before normal measurement operations. This procedure actively reduces remanence and coercive magnetic field effects in the magnetic core, ensuring that the high-sensitivity fluxgate transducer starts from a near-zero offset state. The control circuit is configured to automatically execute this demagnetization sequence, eliminating offset errors before measurements begin.
Solution Approach 2:
The patent employs feedback mechanisms where the control circuit monitors the magnetic core state and adjusts excitation current parameters to maintain optimal operating conditions. This feedback control helps minimize offset errors by compensating for remanence effects in real-time, ensuring reliable measurements despite the high sensitivity of the fluxgate transducer.
3Measurement precision
If fluxgate transducer includes electronics for excitation current and compensation current, then measurement accuracy is improved, but cost and compactness are worsened
Solution Approach 1:
The patent merges the excitation current generation and compensation current control into a single integrated control circuit. The control circuit simultaneously manages the excitation coil drive circuit for magnetic core saturation and the compensation coil for magnetic field cancellation, reducing the total number of separate electronic components while maintaining measurement accuracy. This integration approach lowers cost and improves compactness without sacrificing precision.
4Reliability
If fluxgate transducer is used in closed-loop configuration with compensation coil, then measurement reliability is improved, but device complexity increases
Solution Approach 1:
The patent designs the control circuit to perform multiple functions: generating excitation current, controlling compensation current, executing degauss procedures, and monitoring magnetic core state. This multi-functional control circuit eliminates the need for separate dedicated circuits for each function, reducing overall device complexity while maintaining the reliability benefits of closed-loop operation with compensation coil.
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 cost-effective, reliable, and easily adjustable fluxgate transducer with low offset errors, suitable for safety-critical applications, achieving high sensitivity and compliance with standards like ASIL D.
Implementation Method 1
the excitation coil connected to a control circuit configured to alternatingly saturate the soft magnetic core
Implementation Method 2
the fluxgate transducer measures the intensity of the magnetic field generated by one or more primary conductors carrying the current to be measured
Implementation Method 3
the compensation coil magnetically coupled to the magnetic circuit core and connected in a feedback circuit to a signal processing circuit, the compensation coil seeking to cancel the magnetic field generated by the primary conductor(s)
Data Source
Figure 1a
Figure 1b
Figure 2
AI summary
Fluxgate current transducer (2) including a control circuit (4) and a fluxgate device (2) comprising a saturable soft magnetic core (6) surrounded by an excitation coil (8), the control circuit comprising an excitation coil drive circuit connected to the excitation coil configured to generate an alternating magnetic field to alternatingly saturate the soft magnetic core. The excitation coil comprises a first winding (8a) and a second winding (8b) connected together at a common point (9) forming an input of the first winding and an output of the second winding, the first winding connected in series to a first switch (S1) and the second winding connected in series to a second switch (S2).