Foreign Object Detector Dual-Component Voltage Sensing
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Solution Overview
Problem
Current wireless power transmission systems face challenges in detecting foreign objects, such as metallic objects or human bodies, near coils due to low sensitivity in existing detection methods, which can lead to heating risks and unsafe operation.
Innovation Solution
A foreign object detector that measures both the AC and DC components of the oscillation voltage, enabling high-sensitivity detection by incorporating an oscillator circuit with resonant capacitors and a measurement circuit capable of analyzing variations in both components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If only AC component measurement is used for foreign object detection, then the detection method is simple, but the detection sensitivity is low
Solution Approach 1:
The patent transitions from one-dimensional AC component measurement to two-dimensional measurement by incorporating both AC and DC component detection. The measurement circuit now analyzes voltage variations in both dimensions, enabling more comprehensive foreign object detection with higher sensitivity while maintaining reasonable circuit complexity through efficient use of existing oscillator circuit elements.
2Reliability
If foreign object detection is not performed, then the system operation is simple, but heating risks occur due to undetected metallic objects
Solution Approach 1:
The oscillator circuit serves dual purposes: generating oscillations for wireless power transmission and providing the measurement signal for foreign object detection. The same coil and capacitor components used for power transmission are utilized for detection measurements, eliminating the need for separate dedicated detection hardware and reducing overall system complexity while ensuring safety.
3Measurement precision
If measurement time is extended to improve detection accuracy, then detection precision increases, but transmission efficiency decreases
Solution Approach 1:
The system performs foreign object detection periodically by measuring voltage variations at specific intervals during the oscillation cycle. The measurement circuit captures both AC and DC component variations during designated measurement periods, achieving high detection accuracy without requiring continuous measurement that would reduce power transmission efficiency. The periodic measurement approach balances both detection accuracy and transmission efficiency.
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
The solution allows for reliable detection of foreign objects with improved sensitivity, ensuring safe and efficient wireless power transmission by accounting for both AC and DC voltage variations.
Implementation Method 1
an oscillator circuit including a coil and resonant capacitors and configured to output a voltage including positive cycles, negative cycles, and a DC voltage
Implementation Method 2
when a metallic foreign object is present in a vicinity of the coil and the resonant capacitors, a variation occurs in a voltage output from the oscillator circuit
Data Source
Figure 1~2
Figure 3~4C
Figure 4D~5
AI summary
A foreign object detector includes: an oscillator circuit 100 having a coil 110 and resonant capacitors Cx, Cy, the oscillator circuit 100 being configured to output a voltage which includes an AC component and a DC component, the AC component having a positive cycle and a negative cycle; and an electric circuit for sensing a variation of the AC component and a variation of the DC component in the voltage output from the oscillator circuit 100 when a foreign object approaches the coil 110.