Foreign Object Detection in Wireless Power Receiving Coils
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Solution Overview
Problem
Existing non-contact electric power feeding systems face challenges in precisely detecting foreign objects due to voltage amplitude reductions caused by factors other than foreign object presence, such as power reduction, apparatus failure, or coil misalignment, leading to potential mal-detection of foreign objects.
Innovation Solution
An electric power receiving apparatus with an electric power receiving coil and a measuring coil, where the measuring coil induces a monitoring voltage, and a foreign object detecting portion generates changes in impedance to accurately detect foreign objects based on the induced voltage and current, allowing for precise identification and control of foreign object presence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If voltage amplitude threshold detection is used to identify foreign objects, then foreign object detection capability is provided, but false detection occurs when voltage amplitude reduces due to other causes
Solution Approach 1:
The system continuously monitors impedance changes and uses this feedback to dynamically adjust detection thresholds and distinguish between foreign objects and other causes of voltage reduction. The impedance measurement provides real-time feedback about the magnetic field coupling status, enabling the system to differentiate between foreign object presence and other anomalies.
Solution Approach 2:
Impedance measurement serves as an intermediary parameter that indirectly indicates foreign object presence without being directly affected by voltage amplitude reductions from other causes. By measuring impedance changes in the magnetic field coupling between coils, the system can detect foreign objects while filtering out false detection causes.
2Device complexity
If simple voltage threshold detection is implemented, then detection circuit complexity is reduced, but detection precision deteriorates due to inability to distinguish foreign objects from other voltage reduction causes
Solution Approach 1:
The impedance measurement mechanism serves multiple functions: it detects foreign objects, monitors magnetic field coupling efficiency, and provides information about coil alignment status. This multi-functional approach allows the system to use a single measurement mechanism for multiple detection purposes without significantly increasing complexity.
Solution Approach 2:
The system changes the detection parameter from simple voltage amplitude to impedance, which provides more discriminative information. Impedance changes reflect the actual magnetic field coupling conditions and enable precise differentiation between foreign objects and other causes of voltage reduction, improving detection precision.
3Productivity
If magnetic field strength is increased for quick charging, then power transmission speed is improved, but foreign object heat generation increases causing safety risks
Solution Approach 1:
The system performs preliminary impedance-based foreign object detection before initiating high-power quick charging. By detecting foreign objects in advance using impedance measurements during normal charging or connection phase, the system can prevent high-power operation that would cause dangerous heat generation in foreign objects.
Solution Approach 2:
The system continuously monitors impedance during charging operations and uses this feedback to detect foreign objects in real-time. When a foreign object is detected through impedance changes, the system can immediately adjust or terminate power transmission, preventing excessive heat generation even during quick charging operations.
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
The system effectively detects foreign objects by analyzing changes in impedance, reducing false positives and enabling precise control of power transmission, thereby enhancing the reliability of non-contact electric power feeding systems.
Implementation Method 1
an electric power receiving coil which disposed in a position where a receiving voltage is induced by a magnetic field from an electric power feeding apparatus
Implementation Method 2
when the foreign object composed of an electric conductor enters the magnetic field, an eddy current is generated within the foreign object
Implementation Method 3
the foreign object generates heat by an influence of the Joule heat due to the eddy current
Data Source
AI summary
An electric power receiving apparatus including: an electric power receiving coil disposed in a position where a receiving voltage is induced by a magnetic field from an electric power feeding apparatus; a measuring coil disposed in a position where a monitoring induced voltage as a voltage corresponding to the receiving voltage is induced by the magnetic field; and a foreign object detecting portion generating an amount of change in an impedance of the electric power receiving coil from the monitoring induced voltage and an induced current of the electric power receiving coil, thereby detecting a foreign object in the magnetic field based on the amount of change.