Foreign Matter Detection in Wireless Power Transfer Using Intermediary Coils
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Solution Overview
Problem
Existing non-contact power transmission systems struggle to accurately detect small foreign matters entrapped between transmission and reception coils, as changes in coupling degree due to foreign objects are not always reflected in power transmission characteristics, leading to potential device failures.
Innovation Solution
A foreign matter detecting device is introduced, comprising multiple detection coils and capacitors forming resonance circuits, which supply AC power at a different frequency than the transmission coils, allowing for accurate detection of foreign matters by monitoring voltage changes outside a predetermined reference range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If power transmission characteristics are monitored to detect foreign matter, then detection capability is provided, but small foreign matter cannot be detected because power transmission characteristics do not change
Solution Approach 1:
The patent introduces detection coils as intermediary elements that are electromagnetically coupled to both the transmission coil and reception coil. These detection coils serve as mediators to detect changes in the electromagnetic field caused by small foreign matter, which cannot be detected by monitoring power transmission characteristics alone. The detection coils convert subtle field changes into measurable signals, enabling reliable detection of small foreign matter while maintaining system reliability.
2Measurement precision
If detection coils are added to improve foreign matter detection, then detection accuracy improves, but device complexity increases
Solution Approach 1:
The detection coils serve multiple functions: they are electromagnetically coupled to both the transmission coil and reception coil, enabling them to detect changes in the electromagnetic field caused by foreign matter. This multi-functional design allows the same detection coils to monitor the entire power transmission path without requiring separate detection systems for each coil, thereby improving detection accuracy while minimizing the increase in device 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
This solution enhances the detection accuracy of foreign matters, preventing device failures by distinguishing voltage changes caused by entrapped objects, even if they are smaller than the transmission coils, and avoids interference with power transmission.
Implementation Method 1
A plurality of detection coils disposed so as to be capable of being electromagnetically coupled to each other between a transmission coil of a power transmission device and a reception coil of a power reception device... a plurality of capacitors forming a resonance circuit together with each of the plurality of detection coils
Implementation Method 2
a method of feeding power by electromagnetic induction is known. In the method of feeding power by electromagnetic induction, a primary-side (power transmission-side or power feeding-side) coil (hereinafter referred to as a transmission coil) and a secondary side (power reception side) coil (hereinafter referred to as a reception coil) are electromagnetically coupled
Data Source
AI summary
A foreign matter detecting device includes a plurality of detection coils disposed so as to be capable of being electromagnetically coupled to each other between a transmission coil of a power transmission device and a reception coil of a power reception device between which power is transmitted in a non-contact manner, a plurality of capacitors each forming a resonance circuit together with each of the plurality of detection coils, a power supply circuit supplying AC power having a predetermined frequency to an input coil that is one of the plurality of detection coils, and a detection circuit detecting a voltage of AC power transmitted via the plurality of detection coils from an output coil that one of the plurality of detection coils and is different from the input coil, and detecting foreign matter entrapped between the transmission coil and the reception coil according to the voltage detected.