Wireless Charging Coil Position Sensing for Accurate Foreign Object Detection
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Solution Overview
Problem
Current foreign object detection technologies in wireless charging systems do not accurately consider the impact of the relative position between the transmit and receive ends, leading to potential safety hazards from metal foreign objects due to eddy current losses and heat generation.
Innovation Solution
A wireless charging apparatus and method that utilizes the self-inductance of the transmitting coil, current, efficiency, and direct current output voltage to accurately determine the relative position between the transmit and receive ends, employing parameters that vary homogeneously with position changes to enhance detection accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If current foreign object detection technology is used without considering relative position, then the detection process is simple, but the detection accuracy is low and safety problems occur
Solution Approach 1:
The system performs preliminary position detection by measuring parameters (self-inductance, current, efficiency, DC output voltage) before conducting foreign object detection. This preliminary action of obtaining relative position information allows the subsequent FOD process to account for position-dependent variations, improving detection accuracy without requiring a completely new detection methodology
Solution Approach 2:
The system utilizes changes in electrical parameters (self-inductance of transmitting coil, current, efficiency, DC output voltage) that vary with the relative position between transmit and receive ends. By monitoring these parameter variations, the system can determine relative position and compensate for position-induced effects in foreign object detection, thereby improving accuracy without adding complex hardware
2Measurement precision
If relative position is accurately detected using multiple parameters, then foreign object detection accuracy is improved, but the detection process becomes more complex
Solution Approach 1:
The system measures multiple parameters (self-inductance, current, efficiency, DC output voltage) that serve dual purposes: they characterize the wireless power transmission system's operational state and simultaneously provide information about the relative position between transmit and receive ends. This multi-functionality allows position detection without requiring separate dedicated measurement systems
Solution Approach 2:
The system continuously monitors electrical parameters and uses the measured values to determine relative position, which then feeds back into the foreign object detection process. This feedback mechanism allows the system to dynamically adjust detection thresholds and criteria based on actual position, improving accuracy while using standard measurement equipment
3Reliability
If position-dependent detection is implemented, then safety against metal foreign objects is improved, but the detection time increases
Solution Approach 1:
The system obtains relative position information before conducting foreign object detection, allowing the subsequent FOD process to use position-optimized detection criteria. This preliminary positioning step enables more efficient detection by avoiding unnecessary measurements or iterations that would occur with position-agnostic detection methods
Solution Approach 2:
The system exploits the natural variation of electrical parameters with position to enable rapid position determination. By measuring parameters that inherently change with relative position (such as self-inductance and efficiency), the system can quickly infer position information without time-consuming dedicated measurements, thus maintaining fast detection overall
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
Improves the accuracy of foreign object detection by reducing errors in impedance and power loss calculations, thereby enhancing safety by preventing overheating and fire risks from metal foreign objects.
Implementation Method 1
A principle of a wireless charging technology is to transmit electric energy through magnetic field coupling between a transmitting coil at a transmit end and a receiving coil at a receive end
Implementation Method 2
when a metal foreign object exists between the transmit end and the receive end, a changing magnetic field generated between the transmit end and the receive end may generate eddy current losses and heat in the metal foreign object
Data Source
AI summary
A wireless charging apparatus is provided, which includes a transmit end or a receive end. The transmit end includes a transmit end resonant network and an inverter circuit, and the transmit end resonant network includes a transmitting coil. The receive end includes a receive end resonant network and a rectifier circuit, and the receive end resonant network includes a receiving coil. The apparatus further includes a controller which is configured to obtain a relative position between the transmit end and the receive end based on a self-inductance of the transmitting coil and at least one parameter. The at least one parameter includes a current of the transmitting coil, efficiency of a wireless charging system formed by the transmit end and the receive end, and a direct current output voltage at the receive end. There is a single change relationship between the at least one parameter and the relative position.