Wireless Power Coil Q-Factor Monitoring for Foreign Object Detection
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Solution Overview
Problem
Existing wireless power transfer systems face challenges in accurately detecting foreign objects within the transmission range, which can affect power transmission efficiency and safety.
Innovation Solution
A power transmission apparatus calculates the quality factor (Q factor) of its coil over time during a power stop, using this change in electrical characteristics to determine the presence of foreign objects by transmitting a notification based on a monotonically decreasing or non-decreasing trend in these characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If foreign object detection is performed using existing methods (Q factor measurement, short-circuiting coils), then foreign object detection capability is provided, but detection accuracy is insufficient to reliably distinguish between power reception apparatus and foreign objects
Solution Approach 1:
The patent applies dynamics by transitioning from static Q factor measurement to dynamic monitoring of voltage waveform characteristics over time. The system observes the temporal behavior of the voltage waveform during power transmission, specifically analyzing whether the waveform monotonically decreases or exhibits non-monotonic behavior, which enables reliable distinction between power reception apparatus and foreign objects based on their different dynamic responses to the transmitted power.
Solution Approach 2:
The patent changes the detection parameter from a single Q factor value to the temporal pattern of voltage waveform characteristics. By monitoring how the voltage waveform evolves over time (monotonically decreasing vs. non-monotonic), the system transforms the detection approach from measuring a static electrical characteristic to analyzing dynamic behavioral patterns, thereby improving detection accuracy and reliability.
2Measurement precision
If power transmission is continuous, then power transfer efficiency is maintained, but foreign object detection cannot be performed
Solution Approach 1:
The patent implements periodic action by intermittently stopping power transmission at scheduled intervals during the charging process. These periodic pauses are specifically timed and controlled to perform foreign object detection by analyzing the voltage waveform characteristics during the stop periods, while resuming power transmission afterward to maintain overall charging efficiency. This periodic on-off pattern enables both detection and power transfer functions.
Solution Approach 2:
The patent uses the voltage waveform characteristics during power transmission stop as an intermediary indicator for foreign object detection. Instead of directly detecting foreign objects during active power transmission, the system analyzes the behavior of the voltage waveform (whether it monotonically decreases or shows non-monotonic patterns) during brief stop periods, using this intermediate measurement to infer the presence of foreign objects without requiring continuous interruption of power transfer.
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 method enhances the accuracy of foreign object detection, ensuring reliable and efficient power transmission by distinguishing between legitimate power reception devices and foreign objects.
Implementation Method 1
a power transmission coil 303 configured to generate an electromagnetic field so as to wirelessly transmit power
Implementation Method 2
a power reception coil 201 configured to receive power from the power transmission coil 303
Data Source
AI summary
A power transmission apparatus transmits, to a power reception apparatus, if a change in the electrical characteristic during a stop of wireless power transmission is monotonically decreasing, a notification indicating whether to use a received power value to detect a foreign object based on a Q factor, and transmits, to a power reception apparatus, if the change in the electrical characteristic during the stop of wireless power transmission is not monotonically decreasing, a notification indicating that whether to use the received power value to detect the foreign object is not determined.