Measuring Coil Foreign Matter Detection in Wireless Power
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Solution Overview
Problem
Existing noncontact power feeding systems fail to accurately detect foreign matter, leading to erroneous detection due to factors other than the presence of foreign matter, such as decreased power or efficiency issues, and do not account for coil displacement, resulting in incorrect foreign matter identification.
Innovation Solution
A power receiving device with a measuring coil inductively coupled to the power receiving coil, where the measuring coil has concentric turns closer to the axis than the power receiving coil, and a foreign matter detecting section that determines the presence of foreign matter by analyzing impedance changes measured from both coils, using a voltage obtaining circuit and current obtaining circuit to calculate impedance and adjust power levels accordingly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single coil is used for both power receiving and foreign matter detection, then device complexity is reduced, but measurement precision deteriorates due to inability to distinguish foreign matter from other causes of voltage decrease
Solution Approach 1:
The patent divides the single coil function into two separate coils: a power receiving coil for receiving power and a measuring coil for detecting foreign matter. This segmentation allows each coil to be optimized for its specific function, with the measuring coil positioned to detect changes in magnetic flux caused by foreign matter while the power receiving coil handles power transfer.
Solution Approach 2:
The measuring coil acts as an intermediary element that indirectly detects foreign matter by measuring changes in magnetic flux. Instead of directly detecting foreign matter with the power receiving coil, the system uses the measuring coil to sense magnetic field changes and infer the presence of foreign matter through impedance changes.
2Productivity
If power feeding intensity is increased for quick charging, then productivity is improved, but object-affected harmful factors worsen due to increased heat generation from foreign matter
Solution Approach 1:
The patent implements a feedback mechanism where the measuring coil continuously monitors magnetic flux changes during power transfer. When foreign matter is detected through impedance changes in the measuring coil, the system provides feedback to stop or reduce power feeding, preventing excessive heat generation while allowing high-power quick charging to proceed when no foreign matter is present.
Solution Approach 2:
The system performs preliminary detection of foreign matter before initiating high-power charging and continuously monitors during charging. The measuring coil detects foreign matter in advance, allowing the control system to prevent or stop power feeding before dangerous heat levels are reached, enabling safe quick charging operation.
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
Enables accurate detection of foreign matter by distinguishing impedance changes caused by foreign matter from other factors, ensuring correct identification and preventing damage to the system.
Implementation Method 1
a measuring coil configured to detect a change in a magnetic flux
Implementation Method 2
a power receiving coil configured to receive power fed from a power feeding device via a magnetic field
Implementation Method 3
when foreign matter as a conductor is present in the magnetic field, an eddy current occurs within the foreign matter, and the foreign matter may generate heat due to an effect of a Joule heat caused by the eddy current
Implementation Method 4
the foreign matter may generate heat due to an effect of a Joule heat caused by the eddy current
Data Source
AI summary
A power receiving coil and a measuring coil are in a power receiving device. The measuring coil is inductively coupled to the power receiving coil. Concentric turns of a wire in the measuring coil are around a common axis. Also around the common axis are concentric turns of a wire in the power receiving coil. At least one of the concentric turns of the wire in the measuring coil is closer to the common axis than each of the concentric turns of the wire in the power receiving coil. A power feeding device receives a control signal from the power receiving device. The control signal instructs the power feeding device to adjust a power level of an electromagnetic wave emission.