Detection Coil for Wireless Power Foreign Matter Detection
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Solution Overview
Problem
Existing wireless power supply devices face challenges in accurately detecting foreign matter due to induced voltages generated even in the absence of conductive foreign matter, leading to potential false detection.
Innovation Solution
A foreign matter detection device with a detection coil positioned between the power transmitting and receiving coils, featuring a continuous conductive wire with loop portions wound in opposite directions, set to minimize induced voltage when no foreign matter is present, and a detection unit to compare induced voltages with a reference voltage to determine the presence of conductive foreign matter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a third coil is interposed between a first coil and a second coil to detect foreign matter, then foreign matter detection capability is provided, but induced voltage is generated even without foreign matter causing false detection
Solution Approach 1:
The detection coil is divided into multiple independent coils arranged in specific patterns. Each coil detects magnetic flux changes independently, and their signals are combined to distinguish foreign matter detection from background induced voltage, resolving the contradiction between detection capability and false alarm reduction.
Solution Approach 2:
Multiple detection coils are arranged asymmetrically with different orientations and positions relative to the primary and secondary coils. This asymmetric arrangement causes foreign matter to produce distinct detection signals compared to the symmetric background induced voltage, enabling accurate foreign matter detection while minimizing false positives.
2Measurement precision
If a detection coil is positioned between power transmitting and receiving coils to detect foreign matter, then foreign matter presence can be detected, but induced voltage generation reduces detection sensitivity
Solution Approach 1:
The harmful induced voltage component is extracted and separated from the useful foreign matter detection signal through differential measurement techniques. By comparing signals from multiple coils with different orientations, the common-mode induced voltage is removed while preserving the foreign matter-induced differential signals.
Solution Approach 2:
Multiple detection coils serve as intermediaries that transform the magnetic flux changes into electrical signals with different characteristics. By processing and comparing these intermediate signals, the system can distinguish foreign matter effects from background induced voltage, enhancing detection sensitivity while reducing interference.
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 configuration reduces false detection by minimizing induced voltage when no foreign matter is present, enhancing detection sensitivity and preventing wrongful detection.
Implementation Method 1
a detection unit configured to detect an induced voltage generated in the detection coil and detect, from the detected induced voltage, presence or absence of a conductive foreign matter positioned between the power transmitting coil and the power receiving coil
Implementation Method 2
the detection coil includes a continuous conductive wire in which two loop portions are wound in mutually opposite directions, and an area or a winding number of each of the loop portions or a direction connecting centroids of the two loop portions is set so that an induced voltage generated in the detection coil when a conductive foreign matter is not present becomes 0 or a minimum
Implementation Method 3
when a metal foreign matter enters space between the primary coil and the secondary coil, there is a possibility that an eddy current is generated in the metal foreign matter and the metal foreign matter heats by Joule heat
Implementation Method 4
the metal foreign matter heats by Joule heat
Data Source
AI summary
A foreign matter detection device including a detection coil between a power transmitting coil and a power receiving coil, and a detection unit detecting an induced voltage V generated in the detection coil and detects, from this induced voltage, presence or absence of a conductive foreign matter between the power transmitting coil and the power receiving coil. The detection coil includes a continuous conductive wire where two loop portions are wound in mutually opposite directions. An area or a winding number of each loop portion or a direction connecting centroids of the two loop portions is set so that the induced voltage (i.e., a reference voltage) generated in the detection coil when no conductive foreign matters exist becomes 0 or a minimum.