TMR Sensor Leakage Current Detection for EV Chargers
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Solution Overview
Problem
Current leakage current detection technologies for electric vehicle chargers, such as fluxgate and Hall sensors, are costly and inefficient for detecting lower leakage current levels required by the IEC 62752 standard, as they require complex external circuits and high magnetic field flux levels.
Innovation Solution
A magnetic core with a gap and wound conductors, combined with a tunnel-magnetoresistance (TMR) sensor element, which generates a voltage proportional to the leakage current, allowing for the detection of AC and DC leakage currents up to 30 milliamperes with a cost-effective design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If fluxgate or magnetic modulation current detection technologies are used, then leakage current detection capability is achieved, but device complexity and manufacturing cost increase due to requiring external circuits and magnetic core windings with high number of turns
Solution Approach 1:
The patent combines the magnetic core, windings, and sensor element into an integrated assembly where the TMR sensor is positioned within the magnetic core structure. This merging eliminates the need for separate external driving circuits and magnetic core assemblies, reducing overall system complexity while maintaining leakage current detection capability.
Solution Approach 2:
The patent replaces traditional magnetic field sensing methods with a TMR (tunnel magnetoresistance) sensor that uses quantum mechanical tunneling effects. This substitution eliminates the need for complex magnetic core windings and external driving circuits, simplifying the system architecture while enabling detection of low-level leakage currents.
2Measurement precision
If Hall current sensor technology is used, then high current detection is achieved, but detection of low leakage current levels below 100 Gauss is not possible
Solution Approach 1:
The patent changes the detection parameter from magnetic field flux level (measured in Gauss by Hall sensors) to magnetoresistance voltage signal (measured by TMR sensor). This parameter change enables detection of much weaker magnetic fields corresponding to low leakage currents of 6 milliamperes, expanding the detection range to include both high currents and low leakage currents.
Solution Approach 2:
The patent substitutes Hall effect-based magnetic field detection with TMR-based magnetoresistance detection. This substitution enables the system to detect magnetic field levels as low as those produced by 6 milliamperes of leakage current, providing versatility across both high current and low leakage current detection requirements.
3Reliability
If magnetic core windings with high number of turns are used, then magnetic core reaches expected condition for detection, but manufacturing cost increases
Solution Approach 1:
The patent changes the sensor technology parameter from Hall effect detection to TMR detection, which has different magnetic field sensitivity characteristics. This parameter change allows the use of magnetic core windings with fewer turns while still achieving the required detection sensitivity for 6 milliamperes leakage current, thereby reducing manufacturing cost.
Solution Approach 2:
The patent substitutes traditional magnetic field sensing with TMR sensor technology, which provides higher sensitivity and different operational characteristics. This substitution reduces the requirement for high-number-turn windings to achieve adequate magnetic field strength, simplifying the winding process and reducing manufacturing cost.
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 enables the detection of lower leakage current levels with reduced costs, meeting the IEC 62752 standard requirements by utilizing a high permeability magnetic core and TMR sensor, providing accurate voltage measurements for both AC and DC currents.
Implementation Method 1
a tunnel-magnetoresistance (TMR) sensor element arranged in the gap of the magnetic core. A difference between electric current flow in the first and second conductors produces a magnetic field in the gap of the magnetic core proportional to a leakage current, and the magnetic field produces a voltage in the TMR sensor element indicative of a value of the leakage current.
Data Source
AI summary
An electric current sensor for detecting a leakage current from an electric vehicle charger. The current sensor includes a magnetic core having a gap formed therein, a first conductor wound around the magnetic core to form a first coil, a second conductor wound around the magnetic core to form a second coil, and a tunnel-magnetoresistance (TMR) sensor element arranged in the gap of the magnetic core. A difference between electric current flow in the first and second conductors produces a magnetic field in the gap of the magnetic core proportional to a leakage current, and the magnetic field produces a voltage in the TMR sensor element indicative of a value of the leakage current.