Wireless Charger Foreign Object Detection Using Resonant Q Thresholds
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Solution Overview
Problem
Existing wireless charging systems face challenges in accurately detecting foreign objects, which can lead to reduced efficiency, overheating, and potential damage due to increased ambient temperature and power waste.
Innovation Solution
A method and apparatus for detecting foreign objects using a wireless power transmitter that measures quality factor and inductance values of a resonant circuit before a ping phase, determines a threshold value based on a reference quality factor, and compares these values to accurately identify foreign objects, with the threshold value adjusted by a weight that increases with the reference quality factor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If wireless power transmission is performed using electromagnetic induction or resonance, then power can be transferred wirelessly to devices, but foreign objects in the charging area may be heated due to induced electromagnetic signals
Solution Approach 1:
The system performs foreign object detection before initiating full wireless power transmission by measuring quality factor values during a ping phase. This preliminary detection identifies potential foreign objects that could be heated, allowing the system to prevent power transmission to areas with foreign objects present
Solution Approach 2:
The system continuously monitors the quality factor of the resonant circuit during power transmission and compares it against dynamically determined thresholds. When the quality factor drops below the threshold indicating foreign object presence, the system provides feedback to stop or reduce power transmission, preventing foreign object heating while maintaining efficient wireless charging when safe
2Measurement precision
If traditional foreign object detection methods are used, then detection capability is limited, but system complexity and power consumption increase
Solution Approach 1:
The system uses the existing resonant circuit components and quality factor measurement capabilities for both wireless power transmission control and foreign object detection purposes. The same hardware infrastructure serves multiple functions, avoiding the need for separate dedicated detection systems and reducing overall device complexity
Solution Approach 2:
The system dynamically adjusts detection thresholds based on the reference quality factor value received from the wireless power receiver. This adaptive thresholding improves detection accuracy across different operating conditions and receiver types without requiring complex fixed-threshold systems, optimizing the balance between detection precision and system simplicity
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 enhances the accuracy of foreign object detection, minimizing power waste and equipment damage by dynamically adjusting the threshold values based on the reference quality factor, thereby improving the reliability of wireless charging systems.
Implementation Method 1
Wireless power transmission or wireless energy transfer refers to technology for wirelessly transmitting electric energy from a transmitter to a receiver using the magnetic induction principle
Implementation Method 2
when two coils are located adjacent to each other and then current is applied to one coil, a magnetic flux is generated to cause an electromotive force in the other coil
Implementation Method 3
If a conductor which is not a wireless power receiver, that is, a foreign object (FO), is present in a wireless charging area, an electromagnetic signal received from a wireless power transmitter may be induced in the FO, thereby increasing in temperature
Implementation Method 4
an electromagnetic signal received from a wireless power transmitter may be induced in the FO, thereby increasing in temperature
Data Source
AI summary
A method of transmitting power by a wireless power transmitter, the method including receiving a plurality of packets including a foreign object detection (FOD) status packet from a wireless power receiver; determining whether a foreign object is present in a charging area of the wireless power transmitter on the basis of the FOD status packet; and transmitting, to the wireless power receiver, a response signal indicating whether the foreign object is present in the charging area of the wireless power transmitter on the basis of a result of the determination, wherein the response signal is determined using a measured peak frequency of a power signal transmitted by the wireless power transmitter and a reference peak frequency included in the FOD status packet received from the wireless power receiver, wherein the plurality of packets further include at least one of a signal strength packet, an end power transfer packet, a power control hold-off packet, a control error packet, a renegotiation packet, an eight-bit received power packet, and a charging status packet, to which a byte encoding technique is applied, and wherein the byte encoding technique is a technique of inserting a start bit, a stop bit, and a parity bit into an encoded binary bit stream of a packet having a length of eight bits.