Wireless Charging Flux Control for Foreign Object Heating
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Solution Overview
Problem
Wireless power transfer systems face challenges in controlling magnetic flux density, leading to undesirable heating of foreign metal objects, which complicates and costs foreign object detection systems, especially when detecting small objects.
Innovation Solution
The system measures or estimates peak magnetic flux levels and adjusts electrical currents in the transmit and receive coils to reduce magnetic flux density while maintaining sufficient power transfer, using a controller to determine and adjust current levels based on measured or estimated flux levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If magnetic flux density is increased to improve power transfer efficiency, then power transfer efficiency is improved, but heating of foreign metal objects increases
Solution Approach 1:
The patent implements dynamic adjustment of transmit coil current based on real-time magnetic flux density measurements. The system continuously monitors flux density at the surface and adjusts the current level to maintain it below a threshold, thereby dynamically balancing power transfer efficiency with prevention of foreign object heating.
Solution Approach 2:
The patent changes the operating parameter (current level) of the transmit coil based on measured magnetic flux density. By adjusting the current parameter dynamically, the system optimizes power transfer while ensuring flux density remains below thresholds that would cause harmful heating of foreign objects.
2Measurement precision
If foreign object detection sensitivity is increased to detect smaller objects, then detection capability is improved, but system complexity and cost increase
Solution Approach 1:
The patent introduces magnetic flux density measurement as an intermediary parameter to indirectly detect the presence of foreign objects. Instead of using complex direct detection methods, the system measures flux density at the surface, which naturally increases near foreign objects, providing a simpler and more cost-effective detection mechanism.
Solution Approach 2:
The patent replaces complex mechanical or electronic foreign object detection systems with a magnetic field-based measurement approach. By using magnetic flux density sensors to detect changes in the magnetic field caused by foreign objects, the system achieves high detection sensitivity without requiring complex mechanical scanning or multiple sensor arrays.
3Reliability
If magnetic flux density is reduced to prevent foreign object heating, then safety is improved, but power transfer capability decreases
Solution Approach 1:
The system dynamically adjusts the transmit coil current based on real-time flux density measurements and foreign object detection. When no foreign objects are detected, the system operates at higher current levels to maximize power transfer. When foreign objects are detected or flux density approaches thresholds, the system reduces current to prevent heating, thereby dynamically optimizing both safety and power transfer capability.
Solution Approach 2:
The patent implements a feedback control loop where magnetic flux density measurements are continuously monitored and used to adjust transmit coil current. This feedback mechanism ensures that power transfer is optimized when safe, while automatically reducing power when foreign objects are detected, balancing safety requirements with power transfer needs.
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 reduces magnetic flux density at the surface of the wireless charging pad, preventing excessive heating of foreign objects and simplifying foreign object detection systems, thereby reducing overall system complexity and cost.
Implementation Method 1
a transmit coil configured to inductively transfer power to a receive coil via a magnetic field
Implementation Method 2
a receive coil configured to inductively receive power via a magnetic field
Implementation Method 3
Reducing the flux density reduces heat produced in foreign metal objects that are affected by the magnetic field generated by the coils
Data Source
AI summary
The present disclosure describes techniques for estimating or measuring changes in peak magnetic flux levels based on the influence of a receive coil to the overall flux density over a transmit coil. The estimated or measured changes in peak magnetic flux levels are used to adjust currents in the coils to reduce the flux density while maintaining sufficient power transfer. In some aspects, an apparatus for controlling power transfer is provided. The apparatus includes a controller configured to receive or determine a measured or estimated magnetic flux level on or outside a housing configured to house a transmit coil. The controller is further configured to determine an electrical current level for at least one or both of the transmit coil or a receive coil that reduces a peak magnetic flux density level in proximity to the transmit coil based on the measured or estimated magnetic flux level.