Capacitance Sensing for Foreign Object Detection in Wireless Charging
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Inductive wireless energy transfer systems face challenges in managing heat generated by foreign objects (FO) during energy transfer, leading to inefficiencies and potential damage due to eddy currents, and existing methods like power loss detection may inadvertently emit energy to FOs, causing unnecessary heat.
Innovation Solution
A capacitance sensing structure is integrated near the wireless charging unit to detect foreign objects by sensing changes in capacitance, allowing for the deactivation of the wireless charging unit to prevent energy transfer and reduce heat generation, and a method to distinguish between foreign objects and compatible charging devices based on predefined capacitance values or ranges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If power loss detection method is used to regulate transmitted power, then energy transfer efficiency is improved, but foreign objects may still be heated due to continuous energy emission
Solution Approach 1:
The system performs foreign object detection before initiating power transmission by measuring capacitance values of sensing elements. This preliminary detection prevents energy emission to foreign objects before heating can occur, while still enabling efficient energy transfer when no foreign objects are present
2Speed
If transmitted power is regulated to high value for normal operation, then charging speed is improved, but foreign objects present in the field may generate excessive heat
Solution Approach 1:
Capacitance sensing elements act as intermediary detectors between the power transmission system and foreign objects. These sensing elements detect the presence of foreign objects through capacitance measurements, enabling the system to prevent high-power transmission when foreign objects are detected, thus avoiding heat generation while maintaining fast charging capability when safe
3Reliability
If foreign object detection sensitivity is increased to detect all foreign objects, then safety is improved, but false detection of compatible charging devices may occur
Solution Approach 1:
The system uses multiple capacitance sensing elements with different sensing characteristics positioned at different locations. Each sensing element has optimized capacitance values suitable for detecting specific types of foreign objects. The evaluation unit analyzes patterns across multiple sensing elements to distinguish foreign objects from compatible charging devices, achieving both high detection sensitivity and device compatibility
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
Effectively detects foreign objects and prevents heat generation by deactivating the wireless charging unit when foreign objects are present, enhancing the efficiency and safety of the wireless charging process.
Implementation Method 1
A capacitance sensing element of the plurality of capacitance sensing elements is configured to sense a capacitance representative
Implementation Method 2
inductive based wireless energy transfer systems
Implementation Method 3
heat generated by eddy currents in so called Foreign Objects (FO)
Data Source
Figure 1~2
Figure 3a~3b
Figure 4a~4b
AI summary
It is inter alia disclosed to determining whether an object detected (160) based on at least one capacitance representative of at least one capacitance representative sensed by at least one capacitance sensing element (111, 112, 113) of an apparatus (100) corresponds to a predefined type of objects, the apparatus (100) further comprising a wireless charging unit (140), wherein the at least one capacitance sensing element (111, 112, 113) is at least partially placed in proximity to the wireless charging unit (140).