Ring-Core Current Sensor With Duty-Ratio Resampling
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Solution Overview
Problem
Current sensor devices erroneously detect large-amplitude alternating current components as direct current due to magnetic saturation, leading to inaccurate readings.
Innovation Solution
A self-oscillating current sensor device with a resampling mechanism that uses a duty ratio calculation, clock introduction, and low-pass filtering to accurately distinguish between direct and alternating currents, independent of oscillation frequency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If a self-oscillating circuit is used to detect current, then the device can operate autonomously without external clock signals, but the oscillation frequency varies with current amplitude causing erroneous detection of alternating current components
Solution Approach 1:
The patent introduces a duty ratio calculation unit that converts the oscillation signal into a duty ratio value, and a low-pass filter that processes this duty ratio signal. This intermediary processing chain separates the measurement from the variable oscillation frequency, allowing accurate DC detection while filtering out AC components regardless of frequency variations.
Solution Approach 2:
The patent changes the parameter being measured from direct current amplitude to duty ratio of the oscillation signal. By measuring duty ratio instead of direct current amplitude, the system becomes immune to frequency variations caused by large-amplitude alternating current components, while still accurately detecting DC current through duty ratio changes.
2Productivity
If the magnetic core operates at high current amplitudes, then the sensor can handle large currents, but magnetic saturation occurs causing alternating current components to be detected as direct current
Solution Approach 1:
The duty ratio calculation unit acts as an intermediary that processes the oscillation signal through duty ratio measurement and low-pass filtering. This intermediary mechanism allows the system to handle large current amplitudes without magnetic saturation errors, as the duty ratio measurement method inherently filters out alternating current components even when present at high amplitudes.
3Adaptability or versatility
If the oscillation frequency varies with current amplitude, then the sensor adapts to different current levels, but frequency variation causes alternating current components to be erroneously detected
Solution Approach 1:
The patent changes the measurement parameter from frequency-dependent current amplitude to duty ratio. This parameter change allows the system to maintain adaptability to different current levels through duty ratio variations while achieving excellent alternating current rejection, as the low-pass filter on the duty ratio signal eliminates frequency-related errors.
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 device effectively differentiates between direct and alternating currents, preventing erroneous detection even with large-amplitude alternating components, ensuring accurate current measurement.
Implementation Method 1
a magnetic core with a ring shape. A secondary conductor is wound on the magnetic core, and a primary conductor extends through a central hole of the magnetic core
Data Source
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AI summary
A current sensor device comprises a self-oscillating circuit, a duty ratio calculation portion, a clock introducing portion, a resampling portion and a low-pass filter. The self-oscillating circuit has a magnetic core with a ring shape. A primary conductor extends through a central hole of the magnetic core. The self-oscillating circuit generates a pulse signal in response to a current flowing through the primary conductor and operates based on the pulse signal. The duty ratio calculation portion calculates a duty ratio of the pulse signal and outputs a duty ratio signal. The clock introducing portion generates a clock signal having a constant frequency. The resampling portion resamples the duty ratio signal based on the clock signal. The low-pass filter integrates the resampling signal.