Sequential Detection Coils for Inductive Power Transfer FOD
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Solution Overview
Problem
Existing wireless power transfer systems face challenges in accurately detecting foreign objects, especially small ones, due to low energy loss differences in high power applications and sensitivity to mechanical variations, which can lead to false triggers and increased complexity with multiple coils required for detection.
Innovation Solution
A foreign object detection system using a plurality of coplanar detection coils in tank circuits, where each coil can be selectively operated independently to avoid interference and maintain equal resonance frequencies, allowing for reliable size and location determination of foreign objects without continuous power transfer interruption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple auxiliary coils and detector coils are used for foreign object detection, then detection capability is improved, but device complexity increases
Solution Approach 1:
The transmitter coil serves dual functions: it acts as both the power transmission coil and the detection coil for foreign object detection. By using the same coil for both power transfer and detection purposes, the patent eliminates the need for separate auxiliary coils and detector coils, thereby reducing device complexity while maintaining detection capability.
Solution Approach 2:
The patent merges the function of the transmitter coil with the detection coil function. Instead of having separate coils for power transmission and foreign object detection, the system combines these functions into a single coil system, reducing the total number of components and simplifying the overall device structure.
2Measurement precision
If detector coils are used for foreign object detection, then detection precision is improved, but sensitivity to mechanical variation increases causing false triggers
Solution Approach 1:
The system continuously monitors the impedance of the transmitter coil and uses this feedback information to detect foreign objects. By comparing impedance changes against expected values and patterns, the system can distinguish between actual foreign objects and variations caused by mechanical displacement of ferrite materials, thereby reducing false triggers while maintaining detection precision.
Solution Approach 2:
The patent monitors changes in electrical parameters (impedance, resonant frequency) of the transmitter coil to detect foreign objects. By analyzing parameter changes rather than relying on fixed threshold detections, the system can adapt to mechanical variations and distinguish between normal operational changes and actual foreign object presence, reducing false triggers.
3Reliability
If power transfer is interrupted for foreign object detection, then detection reliability is improved, but productivity decreases
Solution Approach 1:
The system performs foreign object detection continuously during power transfer by monitoring the impedance of the transmitter coil in real-time. This allows the charging process to continue without interruption while simultaneously detecting foreign objects, thereby maintaining both detection reliability and charging productivity.
Solution Approach 2:
The transmitter coil performs dual functions simultaneously: power transmission and foreign object detection. By using the same coil for both purposes and monitoring its electrical characteristics during operation, the system eliminates the need to interrupt power transfer for detection, ensuring continuous charging while maintaining reliable foreign object detection.
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 solution enables more accurate and reliable detection of foreign objects, reduces processor usage, and minimizes component costs by allowing continuous monitoring without interference from other coils, while being less sensitive to mechanical variations and non-dissipating magnetic materials.
Implementation Method 1
The detection coils are configured for generating an electromagnetic field to detect foreign objects in a predetermined space
Implementation Method 2
the plurality of detection coils have equal self-inductance such that, when connected to the respective tank circuits, the detection coils have substantially equal resonance frequencies
Implementation Method 3
Metallic or conductive foreign objects for instance may absorb the electromagnetic field in part through induced eddy currents and as a consequence generate heat
Data Source
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AI summary
Apparatus (10) for wireless power transfer, comprising a power transfer coil (11) configured for inductive power transfer and a foreign object detecting device (20) comprising a plurality of detection coils (211-213). The foreign object detecting device comprises a driver module (50) coupled to the plurality of detection coils (21) for generating a magnetic field with the plurality of detection coils. The driver module is configured to operate the plurality of detection coils sequentially, e.g. only one of the plurality of detection coils being connected to the driver module at a time.