Wireless Charging Power Control With ACK/NAK Foreign Object Detection
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Solution Overview
Problem
Current wireless charging technologies face challenges in accurately detecting foreign objects, leading to inefficient power transmission and potential device damage due to overheating, as they often incorrectly determine the presence of foreign objects, resulting in unnecessary charging stops or continued charging with reduced efficiency.
Innovation Solution
A method and apparatus for controlling wireless power transmission that includes a foreign object detection system using packet reception, determination phases, and adaptive power control, where power transmission modes are adjusted based on the presence of foreign objects, utilizing sensors to measure power loss and temperature changes to accurately detect and respond to foreign objects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If wireless power transmission is performed using electromagnetic induction or resonance, then power can be transmitted wirelessly to devices, but foreign objects in the charging area may be heated causing safety issues and device damage
Solution Approach 1:
The system performs foreign object detection before initiating full power transmission by measuring quality factor during negotiation phase. This preliminary detection prevents foreign objects from being exposed to high power levels that would cause heating, while still allowing wireless charging to proceed when safe
Solution Approach 2:
The system continuously monitors quality factor changes during charging and compares them against threshold values. When quality factor deviation indicates foreign object presence, the system provides feedback to stop or reduce power transmission, preventing foreign object heating while maintaining safe wireless charging operation
2Measurement precision
If foreign object detection is performed using quality factor measurement, then foreign objects can be detected, but false detection occurs when devices are not properly aligned causing unnecessary charging stops
Solution Approach 1:
The system dynamically adjusts the quality factor threshold value based on the negotiation phase status and alignment conditions. During alignment phase, different threshold criteria are applied compared to negotiation phase, allowing the system to distinguish between quality factor changes caused by misalignment versus those caused by foreign objects, reducing false detections while maintaining detection accuracy
Solution Approach 2:
The foreign object detection system transitions from static threshold comparison to dynamic threshold adjustment based on charging phase and alignment status. The system adapts detection sensitivity throughout the charging process, being more lenient during alignment phase and more stringent during power transmission phase, ensuring both accurate detection and charging continuity
3Object-affected harmful factors
If power transmission is stopped when foreign objects are detected, then device safety is improved, but charging efficiency decreases due to repeated detection and stopping cycles
Solution Approach 1:
The system performs foreign object detection at specific periodic intervals during the charging process rather than continuously or at every phase transition. Detection is performed during negotiation phase and at designated checkpoints during power transmission, allowing charging to proceed uninterrupted when no foreign objects are present while maintaining safety through periodic monitoring
Solution Approach 2:
Foreign object detection is performed in advance during the negotiation phase before high power transmission begins. This preliminary detection identifies foreign objects early, allowing the system to either prevent charging entirely or proceed with reduced power levels, avoiding repeated stopping cycles during active charging and improving overall charging efficiency while maintaining safety
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 solution enhances the accuracy of foreign object detection, prevents device damage, and ensures seamless charging by dynamically adjusting power transmission, maintaining efficient energy transfer and reducing the risk of overheating.
Implementation Method 1
Wireless power transmission or wireless energy transfer technology refers to technology of wirelessly transmitting electric energy from a transmitter to a receiver using the principle of magnetic induction
Implementation Method 2
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
Implementation Method 3
the temperatures of the wireless power receiver and the wireless power transmitter may increase due to increase in ambient temperature of the FO
Data Source
AI summary
A wireless power transmitter for transmitting power to a wireless power receiver, including a controller configured to determine whether a foreign object is present; and a transmission part configured to transmit wireless power according to whether the foreign object is present, wherein the controller receives a foreign object detection status packet including at least one of a reference quality factor and a reference peak frequency from the wireless power receiver, and detects whether the foreign object is present based on the foreign object detection status packet, wherein the controller transmits a NAK response indicating that the foreign object is present or an ACK response indicating that the foreign object is not present to the wireless power receiver, and wherein the transmission part transmits a first power to the wireless power receiver according to the transmitted NAK response or transmits a second power greater than the first power to the wireless power receiver according to the transmitted ACK response.