Coil Current Sensing for Wireless Power Foreign Object Detection
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Solution Overview
Problem
Current wireless power transfer systems are limited in charging multiple devices simultaneously due to power constraints and inadequate foreign object detection (FOD) capabilities, especially at higher power levels, which affects efficiency and safety.
Innovation Solution
The implementation of a coil current sensing circuit within the transmitter, utilizing analog-to-digital converters (ADCs) to directly measure transmitter coil current and calculate root mean square (RMS) values, enhancing precision in power loss calculation and enabling more accurate foreign object detection, while allowing for multi-coil operation and increased charging area flexibility.
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 accuracy deteriorates due to reduced signal-to-noise ratio
Solution Approach 1:
The patent introduces an intermediary measurement approach by using transmitter coil current as a mediator to detect foreign objects. Instead of relying on direct power loss measurements that suffer from low signal-to-noise ratio at high power levels, the system measures the current through the transmitter coil, which provides a more sensitive and accurate indicator of foreign object presence even at high power transfer levels.
Solution Approach 2:
The patent replaces traditional power-based foreign object detection with an electrical measurement-based detection system. By substituting the mechanical/power measurement approach with electrical current sensing through ADCs, the system achieves higher measurement precision for foreign object detection while maintaining high power transfer capability.
2Productivity
If multiple wireless devices are charged simultaneously, then productivity is improved, but device complexity increases due to multiple transmitter IC chips requirement
Solution Approach 1:
The patent implements multi-functionality within a single transmitter IC chip by enabling it to simultaneously perform power transfer to multiple devices and foreign object detection. The transmitter coil current measurement mechanism serves dual purposes: monitoring power transfer status and detecting foreign objects, allowing one chip to replace multiple chips while maintaining productivity.
Solution Approach 2:
The patent merges multiple functions into a unified transmitter system. By combining multi-device power transfer capability with integrated foreign object detection using a single transmitter IC chip and shared current sensing circuitry, the system reduces overall device complexity while maintaining the ability to charge multiple devices simultaneously.
3Reliability
If foreign object detection sensitivity is increased, then safety is improved, but device complexity increases due to more sensitive FOD schemes
Solution Approach 1:
The patent implements self-service foreign object detection by utilizing the existing transmitter coil current measurement circuitry. The same current sensing mechanism used for power management automatically provides foreign object detection capability, eliminating the need for separate complex FOD hardware and reducing overall device complexity while maintaining high detection sensitivity.
Solution Approach 2:
The transmitter coil current measurement system serves multiple functions simultaneously: power transfer monitoring, power management, and foreign object detection. This multi-functional approach achieves high detection sensitivity without requiring separate complex FOD schemes, thereby reducing device complexity while improving reliability.
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 solution enables high-power wireless charging for multiple devices with improved foreign object detection accuracy, reducing the impact of device position on charging flexibility and enhancing the active charging area, thus ensuring safer and more efficient power transfer.
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
a receiver device, which extracts power from the field and supplies it to an electrical load
Implementation Method 3
the controller is configured to compute a transmitter power loss based on the RMS coil current
Data Source
Figure 1
Figure 2A~2C
Figure 3
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.