Foreign Object Detection in Inductive Charging Systems
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Solution Overview
Problem
Inductive charging systems face safety risks due to foreign objects, particularly metallic ones, which can heat up and cause damage, and pose a risk to people, especially children, during the charging process, as existing detection methods are not cost-effective or reliable.
Innovation Solution
A detection device using an electrical resonant circuit with a signal generator and sensor to detect foreign bodies by measuring changes in the natural frequency and return loss, allowing for the prevention of charging when foreign objects are present, and providing a cost-effective solution with a protective element to prevent direct contact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If inductive charging is performed without contact, then charging convenience is improved, but safety risk increases due to foreign objects heating up
Solution Approach 1:
The detection device performs foreign object detection before initiating the inductive charging process. By using a detection coil to generate a magnetic field and measure impedance changes, the system identifies foreign objects in advance and prevents charging, thereby eliminating the safety hazard before it can occur while preserving the contactless charging convenience.
Solution Approach 2:
A separate detection coil is introduced as an intermediary component between the power source and the charging process. This detection coil independently monitors the charging area for foreign objects without interfering with the main charging coil, allowing the system to maintain contactless charging benefits while adding safety through a dedicated detection mechanism.
2Object-affected harmful factors
If foreign object detection is implemented, then safety is improved, but device complexity increases
Solution Approach 1:
The detection device is integrated into the existing charging system architecture, sharing common components such as the controller and power supply. The detection coil is incorporated alongside the charging coil, and the detection function is combined with the charging control logic, thereby reducing overall system complexity despite adding foreign object detection capability.
Solution Approach 2:
The detection system utilizes the existing magnetic field generation capability of the charging coil for detection purposes as well. By measuring impedance changes in the detection coil that result from foreign object presence, the system achieves detection functionality using the same electromagnetic infrastructure already present in the charging system, minimizing additional complexity.
3Object-affected harmful factors
If detection accuracy is increased to detect all foreign objects, then safety is improved, but cost increases
Solution Approach 1:
The detection system employs a simple impedance measurement approach using basic electronic components rather than expensive advanced sensors. The detection coil and associated circuitry represent a low-cost solution that provides sufficient detection accuracy for safety purposes, avoiding the need for expensive detection technologies while maintaining adequate foreign object identification capability.
Solution Approach 2:
The system replaces complex mechanical or optical detection methods with an electromagnetic field-based detection approach. By measuring changes in the magnetic field and impedance caused by foreign objects, the system achieves accurate detection using simple electrical measurements rather than expensive mechanical sensors or optical systems, thereby reducing manufacturing costs while maintaining detection accuracy.
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
Enhances safety by preventing charging when foreign objects are detected, reducing the risk of damage and injury, while being cost-effective and capable of advanced gap monitoring and object detection.
Implementation Method 1
an electrical oscillating circuit (1), which has at least one coil (4) and/or at least one capacitor (6)
Implementation Method 2
a sensor device (12), which has at least one for this (operated by the AC voltage) Electrical oscillating circuit characteristic electrical variable recorded, wherein the variable characteristic of the electrical circuit is phase information
Implementation Method 3
foreign objects with a metallic content can become a safety risk, since these can also heat up significantly during the charging process
Data Source
Figure 1~2
Figure 3a~3j
Figure 4a~6b
AI summary
A charging arrangement for charging electrically operated devices with a primary coil, which is suitable and intended to generate a magnetic field in order to inductively transfer electrical energy to a secondary coil which is part of the electrically operated device, wherein the charging arrangement includes a detection device for detecting objects. According to the invention, the detection device includes at least one frequency generator which supplies an electrical circuit, which has at least one coil and/or at least one capacitor, with an alternating voltage, and a sensor device which detects at least one electrical quantity characteristic of this electrical circuit operated by the alternating voltage.