Combined Inductive-Thermal Sensing for Wireless Charging FOD
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Solution Overview
Problem
Inductive wireless power transfer systems for electric vehicle charging face challenges in detecting foreign objects, particularly metallic and living objects, within the high magnetic field region, which can lead to undesirable induction heating and safety concerns.
Innovation Solution
A sensing system that combines inductive and thermal sensing using a mediating heat-sensitive material, where the material's property changes with temperature, affecting the electrical characteristics of sense elements, allowing for the detection of foreign objects based on both inductive and thermal effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If inductive wireless power transfer is used to enable wireless charging, then power transfer convenience is improved, but foreign object detection difficulty increases due to high magnetic field exposure
Solution Approach 1:
The patent introduces a mediating heat-sensitive material that acts as an intermediary between the foreign object and the sensing system. This material converts thermal effects into electrical characteristic changes that can be detected by the sensing system, thereby enabling indirect detection of foreign objects in the high magnetic field region without direct exposure risks
Solution Approach 2:
The patent replaces direct thermal sensing with indirect electrical characteristic sensing. Instead of directly measuring temperature or thermal effects in the high magnetic field region, the system uses sense elements that detect changes in electrical characteristics (such as impedance) caused by the mediating material's response to foreign object heating, thus substituting a safer electrical measurement approach
2Power
If magnetic field strength is increased to enable sufficient power transfer, then power transfer efficiency is improved, but induction heating of foreign objects worsens
Solution Approach 1:
The patent implements foreign object detection before full power transfer begins. The sensing system continuously monitors for foreign objects during a preliminary detection phase, allowing the system to identify and alert about foreign objects before increasing magnetic field strength to levels that would cause harmful induction heating
Solution Approach 2:
The patent employs a feedback mechanism where the sensing system continuously monitors electrical characteristics of the mediating material and provides real-time information about foreign object presence. This feedback allows the power transfer system to adjust magnetic field strength dynamically, preventing harmful induction heating while maintaining efficient power transfer when safe
3Measurement precision
If combined inductive and thermal sensing is implemented, then foreign object detection accuracy is improved, but device complexity increases
Solution Approach 1:
The patent combines inductive sensing (detecting changes in electrical characteristics) and thermal sensing (detecting temperature effects through the mediating material) into a unified sensing system. This merging allows the system to detect foreign objects through multiple physical effects simultaneously, improving detection accuracy while using a single integrated sensing architecture rather than separate independent systems
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 by correlating changes in electrical characteristics with the magnetic field, enabling the system to reduce power or alert users to remove objects, ensuring safety and preventing overheating.
Implementation Method 1
the mediating heat-sensitive material has a property that varies as a function of temperature when heated by the foreign object exposed to a second alternating magnetic field
Implementation Method 2
the sense element being configured to sense the foreign object based on the inductive effect related to a first alternating magnetic field
Implementation Method 3
An alternating current passing through the coil (e.g., of a primary wireless power transfer structure) produces an alternating magnetic field. When a secondary wireless power transfer structure is placed in proximity to the primary wireless power transfer structure, the alternating magnetic field induces an electromotive force (EMF) into the secondary wireless power transfer structure according to Faraday's law
Implementation Method 4
The resonant structure may comprise a capacitively loaded inductor forming a resonance substantially at a fundamental operating frequency of the inductive WPT system (e.g., in the range from 80 kHz to 90 kHz)
Implementation Method 5
metallic objects or other objects present in the magnetic field can experience undesirable induction heating due to eddy current loss effects
Implementation Method 6
Therefore, metallic objects or other objects present in the magnetic field can experience undesirable induction heating due to eddy current loss effects
Implementation Method 7
In ferromagnetic metallic objects, induction heating may be even more intense due to additional current displacement (skin) and hysteresis loss effects
Implementation Method 8
In ferromagnetic metallic objects, induction heating may be even more intense due to additional current displacement (skin) and hysteresis loss effects
Data Source
AI summary
A method for detecting a foreign metal object near an inductive wireless power transfer system is based on combined inductive sensing and thermal sensing. A sensing system senses the object based on an inductive or thermal effect. The sensing system includes a sense element which has an electrical characteristic that changes in a presence of the object based on the inductive effect. A mediating heat-sensitive material has a property that varies as a function of temperature and changes the electrical characteristic of the sense element as the property changes. The mediating heat-sensitive material is heated by the foreign object when the foreign object is heated by a magnetic field generated by the wireless power transfer system. A controller measures the electrical characteristic and determines a presence of the object based on the change in the measured electrical characteristics.