Galvanically Isolated FOD Loops for EV Wireless Charging Safety
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Solution Overview
Problem
Foreign metallic objects in the charging path of wireless power transfer systems for electric vehicles can cause safety issues due to heating from intense magnetic fields, as existing systems lack effective detection mechanisms.
Innovation Solution
A foreign object detection system using a transmitting loop structure and a receiving loop structure, galvanically isolated, which generates a magnetic field and detects changes in induced voltage to identify the presence of foreign objects, with a control circuit to manage power transfer and prevent overheating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If wireless power transfer is implemented using intense magnetic fields, then power transfer capability is improved, but foreign metallic objects may heat up causing safety issues
Solution Approach 1:
The system performs foreign object detection before initiating wireless power transfer by measuring the baseline impedance of the transmitting coil. This preliminary measurement allows the system to establish a reference state and compare subsequent measurements during charging to detect foreign objects, preventing heating before it occurs.
Solution Approach 2:
The system continuously monitors the impedance of the transmitting coil during wireless power transfer and compares it against the baseline measurement. When impedance changes indicate the presence of a foreign object, the system provides feedback to the control circuit to adjust or terminate power transfer, preventing harmful heating.
2Reliability
If foreign object detection mechanisms are added to wireless charging systems, then safety is improved, but system complexity increases
Solution Approach 1:
The system uses the transmitting coil's impedance measurement for dual purposes: characterizing the coil's electrical properties for power transfer optimization and detecting foreign objects for safety. This multi-functionality eliminates the need for separate dedicated detection hardware, reducing overall system complexity while maintaining safety.
Solution Approach 2:
The transmitting coil's inherent electrical properties (impedance) are used to detect foreign objects without requiring additional sensors or detection components. The system leverages the coil's own electrical characteristics as the detection mechanism, eliminating the need for separate detection systems and reducing complexity.
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
Effectively detects foreign objects and prevents wireless power transfer if a foreign object is present, ensuring safety by ceasing power transfer and avoiding potential fires.
Implementation Method 1
a magnetic field generated by the transmitting loop structure induces a first voltage in the receiving loop structure
Implementation Method 2
detect a change in a magnitude of the first voltage in the receiving loop structure in response to the presence of the foreign object within the magnetic field
Data Source
AI summary
Techniques for detecting a presence of a foreign object within a region for wirelessly transferring power to charge an electric vehicle are discloses. An example apparatus according to the disclosure includes a foreign object detection (FOD) structure including a transmitting loop structure, a receiving loop structure galvanically isolated from the transmitting loop structure and positioned relative to the transmitting loop structure such that a magnetic field generated by the transmitting loop structure induces a first voltage in the receiving loop structure, wherein the first voltage is below a threshold value, and a control circuit configured to drive the transmitting loop structure and detect a change in a magnitude of the first voltage in the receiving loop structure in response to the presence of the foreign object within the magnetic field.