Balanced Detection Coils for Wireless Charging Foreign Object Sensing
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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 operating conditions, interference from friendly metals, and the impact of communication antennas, leading to suboptimal performance and potential heating risks.
Innovation Solution
The implementation of a power transmitter with balanced detection coils and a communication antenna configuration that compensates for both inductive and capacitive couplings, allowing for improved foreign object detection accuracy and reduced interference from communication antennas, enabling more reliable and efficient power transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional foreign object detection methods are used in wireless power transfer systems, then power transfer functionality is provided, but detection accuracy deteriorates due to interference from communication antennas and friendly metals
Solution Approach 1:
The detection coil is divided into multiple segments arranged in a specific geometric pattern (e.g., hexagonal or circular arrangement). Each segment independently detects electromagnetic signals, and their outputs are combined through vector summation. This segmentation allows the system to distinguish between signals from foreign objects and interference from communication antennas or friendly metals, thereby improving detection accuracy while reducing the harmful effects of interference.
Solution Approach 2:
The detection coil segments are arranged asymmetrically with respect to the communication antenna positions. By positioning the segments at specific angles and distances, the system creates an asymmetric detection pattern that is less sensitive to interference from symmetrically positioned communication antennas and friendly metals. This asymmetric arrangement optimizes the detection of foreign objects while minimizing the impact of known interference sources.
2Reliability
If detection sensitivity is increased to detect foreign objects, then detection capability is improved, but false detections from friendly metals increase
Solution Approach 1:
The system implements a feedback mechanism where the output from each detection coil segment is processed and combined in a controlled manner. The vector summation of segment outputs provides feedback that helps distinguish between genuine foreign object signals and interference from friendly metals. By analyzing the phase and amplitude relationships between segment outputs, the system can filter out consistent interference patterns from friendly metals while maintaining sensitivity to foreign objects, thereby improving both reliability and reducing false detections.
3Device complexity
If communication antenna is placed close to detection coil for compact design, then device complexity is reduced, but detection accuracy deteriorates due to electromagnetic coupling
Solution Approach 1:
The detection coil is segmented into multiple sections positioned at different locations and orientations relative to the communication antenna. This segmentation allows the system to maintain a compact overall design while distributing the detection function across multiple points. The segmented structure reduces the impact of electromagnetic coupling from the communication antenna on any single detection point, thereby maintaining detection precision in a compact configuration.
Solution Approach 2:
Different segments of the detection coil are positioned in locations with varying degrees of electromagnetic coupling to the communication antenna. By strategically placing segments in areas with different coupling characteristics, the system ensures that at least some segments maintain high detection precision despite the compact arrangement. This local optimization of detection quality compensates for the overall proximity to the communication antenna.
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 and reliability, particularly at higher power levels, while reducing complexity and cost, and allows for improved communication performance, minimizing false detections and heat risks.
Implementation Method 1
a transmitter coil arranged to generate an electromagnetic test field for foreign object detection
Implementation Method 2
a set of detection coils arranged to detect a foreign object in response to an output signal from the set of detection coils
Implementation Method 3
a communication antenna arranged with a first segment of the first communication coil having a first coupling to the first detection coil and a second segment of the second coil having a second coupling to the second detection coil
Data Source
AI summary
A power transmitter comprises a transmitter coil (103) generating an electromagnetic field. A set of balanced detection coils (207, 209) comprises detection coils in series and compensating each other. A foreign object detector (205) performs foreign object detection, by potentially detect a foreign object in response to a property of an output signal from the set of balanced detection coils (207, 209) in response to the electromagnetic test meeting a foreign object detection criterion. A communicator (211) is coupled to a communication antenna (213) communicates with a power receiver (105) via this. The communication antenna (213) comprises a plurality of communication coils (215, 217) coupled in parallel. A first segment of a first communication coil (215) has a first coupling to a first detection coil and a second segment of a second coil (217) has a second coupling to a second detection coil. The couplings are capacitive and/or inductive couplings and the first coupling and the second coupling compensate each other in the output signal.