Coil Current Sensing for Wireless Power Foreign Object Detection
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Solution Overview
Problem
Current wireless power transfer systems face limitations in high-power charging for multiple devices due to inadequate foreign object detection (FOD) capabilities, especially at higher power levels, which can lead to inefficient energy transfer and safety issues.
Innovation Solution
The implementation of a coil current sensing method within the wireless power transmitting device to determine coil current values, compute transmitter power loss, and detect foreign objects by monitoring changes in power loss that meet specific threshold conditions, enhancing FOD accuracy and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If high power levels are used for wireless charging, then charging speed and power transfer efficiency are improved, but foreign object detection sensitivity deteriorates due to reduced signal-to-noise ratio
Solution Approach 1:
The patent introduces coil current sensing as an intermediary measurement method to detect foreign objects. Instead of relying on direct power loss measurements that become noisy at high power levels, the system uses coil current as a mediator signal that provides better sensitivity. The coil current sensing circuit measures the current through the transmitter coil, and changes in this current indicate the presence of foreign objects, thereby resolving the contradiction between high power operation and detection sensitivity.
Solution Approach 2:
The patent replaces the traditional power loss-based detection method with a coil current sensing method. This substitution changes the measurement approach from monitoring overall power loss (which has poor signal-to-noise ratio at high power) to directly sensing coil current, providing a more sensitive and reliable foreign object detection mechanism that works effectively at high power charging levels.
2Productivity
If multiple wireless devices are charged simultaneously, then productivity is improved, but device complexity increases due to need for multiple transmitters or advanced FOD mechanisms
Solution Approach 1:
The patent implements a single wireless transmitter with multi-coil capability that can charge multiple devices simultaneously. The coil current sensing circuit is designed to monitor multiple transmitter coils within one device, allowing the system to provide universal charging service to multiple receivers without requiring multiple separate transmitter units. This reduces system complexity while maintaining high productivity.
Solution Approach 2:
The patent divides the transmitter into multiple independent coils, each capable of independently charging a device. The coil current sensing circuit can selectively monitor individual coils or combinations of coils, allowing flexible configuration for charging one or multiple devices simultaneously. This segmentation approach enables multi-device charging within a single transmitter unit without proportionally increasing overall system complexity.
3Device complexity
If traditional FOD methods are used, then device complexity is kept low, but measurement precision of foreign object detection is insufficient at high power levels
Solution Approach 1:
The patent introduces coil current sensing as an intermediary measurement that provides better signal characteristics for foreign object detection. The coil current serves as a mediator between the power transfer process and the detection mechanism, offering improved measurement precision without requiring complex additional hardware. This intermediary approach maintains relatively simple device architecture while significantly enhancing detection accuracy at high power levels.
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 allows for precise detection of foreign objects, improving the X-Y placement freedom and safety during high-power wireless charging, enabling simultaneous charging of multiple devices with increased active charging area and reduced transmitter heating.
Implementation Method 1
a transmitter device, driven by electric power from a power source, generates a time-varying electromagnetic or magnetic field, which transmits power across space to a receiver device
Implementation Method 2
determining, via a coil current sensing circuit at the wireless power transmitting device, a coil current value corresponding to a first coil current that passes through a first transmitter coil
Data Source
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AI summary
Embodiments described herein provide foreign object detection based on coil current sensing. The transmitter power loss is computed directly based on the coil current, in conjunction with, or in place of the conventional computation based on transmitter input current. The enhanced precision of the computer power loss can be used to more accurately detect a foreign object near the transmitter coil during a wireless power transfer.