Fluxgate Excitation Circuit Using Pulsed Current Mirror
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Solution Overview
Problem
Conventional excitation circuits for fluxgate sensors are inefficient in terms of power consumption and costly to implement, particularly due to their dependence on sinusoidal excitation waveforms, and they struggle with integration in sensor designs.
Innovation Solution
A pulsed current source coupled with a switched current mirror circuit provides a periodic bidirectional excitation current waveform to the excitation coil, independent of power supply voltage and sensor impedance, using a control circuit to manage the current flow through a bridge circuit with transistors and switches.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If sinusoidal excitation waveform is used, then predictable harmonic content is achieved, but power consumption efficiency deteriorates and circuit implementation cost increases
Solution Approach 1:
The patent employs periodic square wave excitation instead of sinusoidal excitation. The square wave is generated by alternately switching between positive and negative voltage levels applied to the excitation coil, creating a periodic bidirectional current waveform that drives the fluxgate sensor core through magnetic saturation cycles while consuming less power and simplifying circuit implementation.
2Measurement precision
If sinusoidal excitation waveform is used, then predictable harmonic content is achieved, but circuit implementation complexity increases
Solution Approach 1:
The periodic square wave excitation is generated using simple switching circuitry that alternates between positive and negative voltage levels, eliminating the need for complex sinusoidal waveform generation circuits while maintaining predictable harmonic characteristics suitable for fluxgate sensor operation.
Solution Approach 2:
The patent extracts only the essential excitation function needed for fluxgate operation, using a simplified square wave generator that provides the necessary periodic bidirectional current without the complexity of sinusoidal waveform generation circuits, thereby reducing overall device complexity.
3Use of energy by moving object
If voltage pulse excitation is used, then power consumption efficiency improves, but excitation current becomes dependent on supply voltage and sensor impedance
Solution Approach 1:
The patent employs feedback control through a current sense resistor that monitors the actual excitation current flowing through the sensor. This sensed current is fed back to a control circuit that adjusts the switching duty cycle or voltage levels to maintain a predetermined target current, thereby compensating for variations in supply voltage or sensor impedance and ensuring consistent excitation conditions.
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 approach reduces power consumption and simplifies the circuit design, providing efficient and independent excitation with minimal dependence on supply voltage and sensor characteristics, facilitating low-power operation and easy integration in magnetic sensors.
Implementation Method 1
The excitation circuit includes a pulsed current source and a switched current mirror circuit that provides a periodic bidirectional excitation current waveform to an excitation coil of a magnetic sensor
Data Source
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AI summary
In described examples, magnetic sensor excitation circuitry (20) provides a periodic bidirectional excitation waveform to a fluxgate magnetic sensor excitation coil (10a, 10b, 10c, 10d) using a bridge circuit (Q1, Q2, Q3, Q4) connected to the excitation coil (10a, 10b, 10c, 10d) and having lower transistors (Q3, Q4) for switched selective connection to a current mirror input transistor (Q5) to mirror a current provided by pulsed current source (22), and with integrated filtering (R1, CP) to control pulse rise times and slew rate.