Differential Coil Mat Detection for Foreign Objects in WPT
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Solution Overview
Problem
Conventional wireless power transfer systems face safety hazards and efficiency issues due to foreign objects like metal objects heating up and causing power wastage, with existing detection methods being delayed or inefficient.
Innovation Solution
A detection device with a detection mat containing pairs of detection coils having different impedance values, driven by a sub-system to generate a differential current signal, which is processed by a comparison sub-system to generate a control signal for the WPT system to adjust power supply.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional detection methods are used to detect foreign objects in WPT systems, then detection capability is provided, but detection delay occurs resulting in power wastage
Solution Approach 1:
The system performs foreign object detection before initiating wireless power transfer by measuring impedance of detection coils in advance. This preliminary detection prevents power wastage by identifying foreign objects before power is supplied, eliminating the detection delay present in conventional methods that detect during or after power transfer initiation.
2Measurement precision
If detection coils are added to detect foreign objects, then foreign object detection capability is improved, but device complexity increases
Solution Approach 1:
The detection coils are integrated into the existing WPT system infrastructure, serving dual purposes: they function as part of the power transfer system and simultaneously serve as sensors for foreign object detection. This multi-functionality approach improves detection capability without proportionally increasing device complexity, as the same physical infrastructure performs multiple functions.
Solution Approach 2:
The system uses impedance measurement as an intermediary parameter to detect foreign objects indirectly. Instead of requiring direct detection sensors, the system measures electrical impedance changes in the detection coils caused by foreign object presence, providing a simple and effective detection mechanism that avoids complex sensor arrays or additional detection hardware.
3Productivity
If foreign objects are present during wireless power transfer, then power transfer continues, but safety hazards occur due to heating of metal objects
Solution Approach 1:
The system performs foreign object detection before initiating power transfer by measuring impedance of detection coils. This preliminary safety check prevents power transfer from occurring when foreign objects are present, eliminating the safety hazards associated with heating while maintaining productivity by ensuring safe operation conditions are met before activation.
Solution Approach 2:
The system continuously monitors impedance of detection coils and uses this feedback to determine foreign object presence. When impedance changes indicate a foreign object is detected, the system provides feedback to stop or prevent power transfer, creating a closed-loop safety mechanism that prevents hazardous heating while maintaining efficient power transfer when safe.
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 and prevents power wastage by discontinuing power supply to the transmitter unit upon detecting foreign objects, ensuring safety and efficiency in wireless power transfer.
Implementation Method 1
Conventional wireless power transfer (WPT) systems work on a principle of inductive power transfer to wirelessly transfer energy from one device to another
Implementation Method 2
If there is any metal object, such as a metallic can or aluminum foil, present between the transmitter and receiver coils during wireless power transfer, the metal object may be undesirably heated up due to eddy currents
Data Source
AI summary
A detection device (100) includes a detection mat (102) having a plurality of detection coils (106), and at least one pair of groups of detection coils (106), the pair of groups of detection coils (106) includes first and second groups of detection coils (106). The first and second group of detection coils (106) comprises first and second first and second impedance values. The detection device (100) includes one or more drive sub-systems (112) and a comparison sub-system (112). The drive sub-systems (112) are operatively coupled to the detection mat (102) and configured to excite at least one pair of groups of detection coils (106). The comparison sub-system (114) is operatively coupled to the detection mat (102) and configured to receive a differential current signal from the pair of groups of detection coils (106), the comparison sub-system (114) is configured to generate a control signal based on the differential current signal.