Wireless Power Foreign Object Detection With Balanced Coil Thresholding
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Solution Overview
Problem
Current foreign object detection methods in wireless power transfer systems, such as those using the Qi specification, face challenges in achieving accurate detection, especially at higher power levels, due to uncertainties in metal properties and operating conditions, leading to suboptimal performance with potential false detections or missed detections.
Innovation Solution
The implementation of a power transmitter with balanced detection coils that generate an electromagnetic test signal during foreign object detection time intervals, where the coils are arranged to compensate each other, allowing for improved detection accuracy by evaluating imbalances in induced signals, and adapting operating parameters based on physical property data from the power receiver.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If power transmission is performed at higher power levels, then the power transfer capability is improved, but the risk of foreign object heating and detection accuracy deteriorates
Solution Approach 1:
The patent divides the detection function into separate balanced detection coils that are distinct from the power transfer coils. This segmentation allows the detection system to operate independently from the high-power transmission system, preventing interference and enabling accurate foreign object detection even at higher power levels.
Solution Approach 2:
The patent introduces balanced detection coils as an intermediary detection mechanism. These coils generate a test signal and detect imbalances caused by foreign objects without directly participating in the high-power transfer process, thus mediating between the power transmission system and the detection requirement.
2Measurement precision
If foreign object detection sensitivity is increased, then detection accuracy is improved, but the number of false positives increases
Solution Approach 1:
The patent employs multiple sets of balanced detection coils positioned at different locations. Each coil set evaluates local imbalances independently, and the system requires a threshold number of coil sets to indicate an imbalance before triggering a foreign object detection. This local evaluation approach reduces false positives by requiring consistent detection across multiple locations.
Solution Approach 2:
The system incorporates feedback through the evaluation of imbalances from multiple detection coil sets. The foreign object detection is triggered only when a threshold number of coil sets indicate an imbalance, providing a feedback mechanism that filters out spurious detections and improves reliability.
3Measurement precision
If detection coils are added to the power transmitter, then foreign object detection capability is improved, but the device complexity increases
Solution Approach 1:
The balanced detection coils serve multiple functions: they generate the test signal for foreign object detection and simultaneously detect the imbalances caused by foreign objects. This multi-functionality reduces the need for separate detection components and simplifies the overall system architecture.
Solution Approach 2:
The patent combines the test signal generation and imbalance detection functions into a single balanced detection coil structure. By merging these functions, the system achieves improved detection capability without proportionally increasing device complexity.
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 foreign object detection accuracy, reduces false positives, and improves suitability for higher power levels by isolating detection from power transfer interference and adapting to specific conditions, resulting in more reliable and efficient foreign object detection.
Implementation Method 1
power is inductively transferred from a transmitter inductor in a power transmitter device to a receiver coil in the individual devices
Implementation Method 2
a plurality of sets of balanced detection coils coupled in series, each set of balanced detection coils comprising two detection coils arranged such that signals induced in the two detection coils by an electromagnetic field generated by the transmitter coil compensate each other
Implementation Method 3
a driver for generating a drive signal for the transmitter coil, the driver being arranged to generate the drive signal for the transmitter coil to generate the power transfer signal during at least one power transfer time interval of a repeating time frame
Data Source
AI summary
A power transmitter (101) comprises a driver (201) generating a drive signal for a transmitter coil to generate a power transfer signal during a power transfer time interval and an electromagnetic test signal during a foreign object detection time interval. A set of balanced detection coils (207, 209) comprise two detection coils arranged such that signals induced in the two detection coils by an electromagnetic field generated by the transmitter coil compensate each other. A foreign object detector (205) is coupled to the detection coils and performs foreign object detection during the foreign object detection time interval. The foreign object detector (205) is arranged to detect a foreign object in response to a foreign object detection criterion requiring that at least one signal from a set of balanced detection coils (207, 209) exceeds a first threshold and not more than a given threshold number of at least two of the signals exceed a second threshold.