Current Sensor Capacitor Placement to Reduce Magnetic Noise
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Solution Overview
Problem
Conventional current sensors experience noise and reliability issues due to eddy currents generated by magnetic fields when high currents pass through shunt resistors, leading to potential malfunctions.
Innovation Solution
A current sensor design where capacitors are positioned outside the plane of projection of the energizing path on a circuit board, reducing the effects of magnetic fields and temperature increases, and are connected to the power supply circuit to smooth voltage, thereby minimizing noise and ensuring reliable operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the current sensing circuit is disposed so as to be opposed to the shunt resistor, then the current measurement function is achieved, but eddy current is generated on the electrolytic capacitor electrode due to magnetic field, causing noise and reliability degradation
Solution Approach 1:
The patent repositions the capacitor from the traditional planar layout (on the same plane as the shunt resistor and sensing circuit) to a three-dimensional position above or below the circuit board. This spatial relocation removes the capacitor from the magnetic field generation zone, eliminating eddy current effects while preserving its voltage smoothing function. The capacitor is connected to the power supply circuit through conductive paths that do not interfere with the current measurement function.
2Power
If high current passes through the shunt resistor, then the current sensing capability is demonstrated, but magnetic field is generated causing eddy current on capacitor electrode
Solution Approach 1:
The patent extracts the capacitor from the harmful magnetic field zone by positioning it in a separate spatial location (above or below the circuit board plane). This extraction removes the capacitor electrode from the path of magnetic flux generated by high current through the shunt resistor, thereby eliminating the harmful eddy current effect while maintaining the capacitor's essential function of smoothing power supply voltage.
3Ease of manufacture
If the capacitor is positioned on the circuit board plane, then the layout is simple, but the magnetic field affects the capacitor causing noise
Solution Approach 1:
The patent transitions from a two-dimensional planar layout to a three-dimensional spatial arrangement by positioning the capacitor above or below the circuit board. This dimensional change maintains manufacturing simplicity while effectively removing the capacitor from the magnetic field's influence zone, thereby eliminating noise without complicating the overall structure.
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 enhances the reliability of the current sensor by reducing noise and temperature-related issues, improves accuracy by shortening the distance between the resistor and sensing circuit, and allows for a more compact design.
Implementation Method 1
at least one capacitor which is connected to at least one of an input terminal and an output terminal of the power supply circuit to smooth input/output voltage
Implementation Method 2
a resistor through which current passes; a current sensing circuit which measures the current passing through the resistor based on a potential difference between two positions
Implementation Method 3
eddy current is generated on an electrode, which has a large area, of the electrolytic capacitor due to a magnetic field generated when a high current passes through the shunt resistor
Data Source
AI summary
A current sensor, which senses current passing through a harness via a terminal of a battery, includes a resistor through which current passes, a current sensing circuit which measures the current passing through the resistor based on a potential difference between two positions along the direction in which current is passed through the resistor, a power supply circuit which supplies power to the current sensing circuit, and at least one capacitor which is connected to at least one of an input terminal and an output terminal of the power supply circuit to smooth input/output voltage. The resistor includes a flat energizing path, and the capacitor is disposed in an area other than a plane of projection of the energizing path on a board on which the current sensing circuit and the power supply circuit are mounted.