Q-Value Measurement Circuit for Foreign Object Detection in Wireless Power
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Solution Overview
Problem
Existing contactless power transmission systems face challenges in detecting metal foreign substances with high precision, especially during power feed, due to dependence on electromagnetic coupling and frequency of carrier signals, which affects detection accuracy and requires additional sensors, increasing costs and design complexities.
Innovation Solution
A contactless power transmission system that uses a power reception coil and a Q-value measurement circuit with alternating-current signals of different frequencies for power feed and detection, allowing for precise detection of metal foreign substances without interrupting power transmission by distinguishing between power feed and Q-value measurement signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single frequency is used for both power feed and detection, then the system structure is simple, but detection precision deteriorates due to signal interference during power feed
Solution Approach 1:
The patent divides the frequency domain into separate segments: one frequency for power feed and another frequency for Q-value measurement. This frequency segmentation allows both functions to operate simultaneously without mutual interference, resolving the contradiction between system simplicity and detection precision
Solution Approach 2:
The patent changes the frequency parameter to differentiate between power feed and detection functions. By using different frequencies for the same coil, the system maintains structural simplicity while achieving high detection precision through parameter differentiation
2Measurement precision
If additional sensors are added for detection, then detection precision improves, but device complexity and cost increase
Solution Approach 1:
The patent makes the existing coil serve dual functions: power transmission and foreign object detection. By using the same coil for both purposes at different frequencies, the system achieves high detection precision without adding extra sensors, thus avoiding increased device complexity
Solution Approach 2:
The coil performs self-detection by measuring its own Q-value at a different frequency from its power transmission frequency. This self-service capability eliminates the need for separate detection sensors, maintaining system simplicity while improving detection precision
3Productivity
If detection is performed during power feed, then productivity improves, but detection precision deteriorates due to electromagnetic coupling interference
Solution Approach 1:
The patent segments the operational frequencies into distinct bands: power feed operates at one frequency while Q-value measurement operates at another. This frequency segmentation enables simultaneous operation without interference, achieving both high productivity and high detection precision
Solution Approach 2:
The system performs periodic Q-value measurements at a frequency distinct from the continuous power feed frequency. This periodic action at a different frequency allows detection during power feed without suffering from electromagnetic coupling interference
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
Enables high-precision detection of metal foreign substances during power feed, improving detection accuracy and efficiency while reducing design complexities and costs by separating the frequencies for power feed and Q-value measurement.
Implementation Method 1
a power reception coil configured to receive power from a power transmission coil using a first alternating-current signal having a first frequency
Implementation Method 2
a Q-value measurement circuit configured to detect a foreign object within a range of the power reception coil using a second alternating-current signal having a second frequency that is different than the first frequency
Data Source
Figure 1
Figure 2
Figure 3A~3B
AI summary
A detection device includes a coil configured to be electromagnetically coupled with an outside, and a detection section connected to a circuit including the coil. The detection section is configured to measure a Q value of the circuit using an alternating-current signal at a frequency different from a frequency of an alternating-current signal of contactless power feed.