Balanced Coil Foreign Object Detection in Wireless Charging
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Solution Overview
Problem
Current foreign object detection methods in wireless power transfer systems, particularly at higher power levels, face challenges in accuracy due to uncertainties in operating conditions and the influence of friendly metals, leading to suboptimal performance with potential false detections or missed detections.
Innovation Solution
A power transmitter with a transmitter coil and balanced detection coils that generate an electromagnetic test signal during foreign object detection time intervals, using a foreign object detector to identify imbalances exceeding specific thresholds, reducing complexity and improving accuracy for higher power level transfers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional foreign object detection methods are used in wireless power transfer systems, then power transfer can be performed, but detection accuracy deteriorates due to uncertainties in operating conditions and influence of friendly metals
Solution Approach 1:
The patent segments the detection process by using multiple independent detection coils arranged in a balanced configuration. Each coil pair independently monitors specific regions, and their combined output provides comprehensive foreign object detection. This segmentation allows the system to maintain detection accuracy across different operating conditions by distributing the detection function across multiple sensors rather than relying on a single detection method.
Solution Approach 2:
The patent introduces an intermediary balanced detection coil system that mediates between the power transfer process and foreign object detection. The balanced coils act as an intermediary sensing mechanism that can detect foreign objects without interfering with the primary power transfer function. This intermediary system provides accurate detection while being isolated from the uncertainties of the main power transfer operation.
2Reliability
If foreign object detection is performed during power transfer, then safety is improved, but detection accuracy worsens due to variability in power transfer conditions
Solution Approach 1:
The patent implements periodic foreign object detection during the power transfer process. The balanced detection coils continuously monitor for foreign objects at regular intervals, allowing the system to maintain safety while accounting for the dynamic nature of power transfer conditions. This periodic monitoring approach enables the system to detect foreign objects even when power transfer conditions are variable, as each detection cycle independently evaluates the presence of foreign objects.
3Measurement precision
If complex foreign object detection algorithms are used, then detection accuracy is improved, but device complexity increases
Solution Approach 1:
The patent replaces complex algorithmic processing with a simpler physical detection mechanism based on balanced electromagnetic coils. Instead of using sophisticated software algorithms to detect foreign objects, the system uses the physical principle of electromagnetic induction with balanced coil pairs that naturally produce detectable signals when foreign objects are present. This substitution of physical mechanism for computational complexity reduces device complexity while maintaining detection accuracy.
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 approach enhances foreign object detection accuracy, reduces false detections, and improves performance by isolating detection from power transfer variability, making it suitable for higher power levels with reduced complexity and cost.
Implementation Method 1
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 and to generate the drive signal for the transmitter coil to generate an electromagnetic test signal during at least one foreign object detection time interval of the repeating time frame
Implementation Method 2
a plurality of sets of balanced detection coils coupled in series, each set of balanced detection coils comprising two symmetric detection coils arranged such that signals induced in the two detection coils by an electromagnetic field generated by the transmitter coil compensate each other
Data Source
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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.