Wireless Inductive Power Transfer Foreign Object Detection
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Solution Overview
Problem
Existing wireless power transfer systems face challenges in accurately detecting parasitic power loss at higher power levels, leading to potential foreign object heating and unsafe scenarios, particularly due to inaccuracies in estimating transmitted and received power, which can result in false detections or missed detections of foreign objects.
Innovation Solution
The system incorporates a parasitic power loss detector and a foreign object detector that adaptively calibrate the parasitic power loss detection using parameter value sets generated during the power transfer phase, allowing for more accurate and reliable detection of foreign objects by distinguishing between operating conditions with and without foreign objects, thereby reducing user involvement and improving safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If power loss detection is performed by subtracting received power from transmitted power, then foreign object detection capability is provided, but measurement precision deteriorates at higher power levels due to accumulated estimation errors
Solution Approach 1:
The patent introduces an intermediary calibration process that uses a known test load to establish a reference relationship between transmitted and received power. This calibration curve serves as a mediator that accounts for system-specific losses and errors, allowing accurate foreign object detection without being affected by the accumulated estimation errors that plague direct subtraction methods at high power levels.
Solution Approach 2:
The patent changes the detection parameter from direct power loss calculation (PT - PR) to a deviation from a calibrated reference curve. By transforming the detection approach and using calibration data taken at different power levels, the system maintains measurement precision across the full power range, effectively resolving the accuracy deterioration issue at high power levels.
2Device complexity
If a fixed threshold is used for power loss detection, then device complexity is reduced, but adaptability deteriorates when operating conditions change
Solution Approach 1:
The patent implements a dynamic threshold approach where the detection threshold is not fixed but derived from calibration data taken at various power levels. The system adapts the threshold automatically based on the current operating power level by referencing the calibrated relationship between transmitted and received power, thereby maintaining high adaptability without significantly increasing system complexity.
Solution Approach 2:
The patent performs preliminary calibration action before normal operation, establishing a reference curve that captures the system's power transfer characteristics under different conditions. This preliminary characterization enables the system to adapt to changing operating conditions during normal operation without requiring complex real-time adjustments, effectively balancing simplicity and adaptability.
3Reliability
If foreign object detection is performed continuously, then detection reliability is improved, but energy consumption increases
Solution Approach 1:
The patent implements periodic foreign object detection at strategically chosen time points during the power transfer process, rather than continuous monitoring. By performing detection at key moments when the system state is well-defined and using calibration-based thresholds, the system maintains high detection reliability while minimizing energy consumption associated with continuous measurement and processing.
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 approach enhances the reliability and accuracy of foreign object detection during power transfer, reducing the risk of overheating and improving operational safety by continuously monitoring and adapting to dynamic conditions, even at higher power levels.
Implementation Method 1
the magnetic flux generated by the transmitter coil will introduce eddy currents in the metal objects which will cause the objects to heat up
Implementation Method 2
the magnetic flux generated by the transmitter coil
Implementation Method 3
Wireless power transfer, such as e.g. for wireless powering or charging of portable devices
Data Source
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AI summary
A wireless power transfer system includes a power transmitter (101) providing power to a power receiver (105). The system comprises a parasitic power loss detector (207) performing a parasitic power loss detection during a power transfer phase based on an estimated parasitic power loss representing a difference between transmit and receive powers. A parameter processor (209) generates and stores parameter value sets indicative of the transmit and receive powers during the power transfer phase. A foreign object detector (215) performs foreign object detection tests estimating whether a foreign object is present or not. A time processor (217) determines a time window in response to a foreign object detection test indicating that no foreign object is present and a retriever (219) retrieves a group of parameter value sets that correspond to time instants within the time window. An adapter (213) then adapts the parasitic power loss detection based on the retrieved parameter value sets.