Wireless Power Calibration for Foreign Object Detection
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Solution Overview
Problem
Current wireless power transfer systems face challenges in accurately detecting foreign objects within the magnetic field, leading to potential heating hazards due to measurement limitations in power loss accounting, especially as power levels increase beyond 5W, resulting in inaccurate determination of unexpected losses.
Innovation Solution
The implementation of a calibration method that uses gain and offset calculations based on no-load and connected power measurements to improve the accuracy of power loss accounting, allowing for more precise detection of foreign objects and preventing overheating by adjusting transmission power or shutting it down when unexpected losses exceed a threshold.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If power loss accounting is used to detect foreign objects, then foreign object detection capability is provided, but measurement accuracy deteriorates at higher power levels
Solution Approach 1:
The system performs a calibration phase before normal power transfer to establish baseline power measurements. During this preliminary action, the transmitter measures power consumption without a receiver present, storing these calibration values for later comparison during foreign object detection, thereby improving measurement accuracy at higher power levels
Solution Approach 2:
The system changes operational parameters by switching between calibration mode and normal power transfer mode. During calibration, specific power measurement parameters are recorded and stored. During normal operation, these parameters are compared against live measurements to detect foreign objects, allowing accurate detection across varying power levels
2Productivity
If power levels are increased beyond 5W, then charging efficiency is improved, but foreign object detection accuracy deteriorates
Solution Approach 1:
Before high-power charging begins, the system performs calibration measurements to establish baseline power consumption characteristics. These preliminary calibration data points enable accurate foreign object detection even when operating at elevated power levels beyond 5W, maintaining detection accuracy while improving charging efficiency
3Speed
If power transmission is increased to improve charging speed, then charging time is reduced, but risk of overheating increases
Solution Approach 1:
The system continuously monitors power consumption during calibration and operation, comparing actual measurements against expected values. When unexpected power losses indicate foreign object presence or abnormal conditions, the system provides feedback to reduce or terminate power transmission, preventing overheating while enabling high-speed charging under normal conditions
Solution Approach 2:
The calibration process establishes baseline measurements that enable the system to anticipate and prevent overheating conditions before they occur. By having reference data from calibration, the system can detect deviations indicating foreign objects and take preventive action, allowing safer operation at higher power levels
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 significantly reduces errors in power loss measurement, especially at higher power levels, effectively preventing overheating hazards by accurately identifying and responding to foreign objects, thus enhancing safety and efficiency in wireless charging systems.
Implementation Method 1
The aligned coils act as a transformer to wirelessly transfer power from the transmitter to the receiver
Implementation Method 2
The primary method used to detect when a foreign object is present is 'Power Loss Accounting'... to prevent potentially dangerous heating
Data Source
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AI summary
In described examples, an integrated circuit (334) includes a communication (334B) and control unit (334A). The communication and control unit (334) controls an inverter (332) that applies an alternating current output signal to a transmission coil (316) for reception by a receiver. The communication and control unit causes the inverter to provide a first and second transmit powers to the transmission coil, and the communication unit receives a first and second power received signals from the receiver in response to the first and second transmit powers. The communication and control unit determines a first gain and offset using the first transmit power, the first power. When a third transmit power greater than the second transmit power is transmitted by the transmission coil, the communication and control unit determines a second gain and a second offset using the first transmit power, the first power received signal, the third transmit power and a third power received signal.