Detection Coil Layout for Accurate Wireless Charging FOD
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Solution Overview
Problem
Existing wireless charging systems face accuracy issues in foreign object detection due to unbalanced magnetic fields, leading to potential fires, as they struggle to differentiate between induced voltage variations caused by foreign objects and system power source fluctuations.
Innovation Solution
A detection coil with a stacking structure of sub-coils wound in opposite directions and connected in series, along with a control circuit that compensates for induced voltage variations, is used to enhance the accuracy of foreign object detection by offsetting voltages and reducing null regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single conductive pattern (coil) is used for generating magnetic field, then the device structure is simple, but the magnetic field becomes unbalanced and foreign object detection accuracy decreases
Solution Approach 1:
The single conductive pattern is divided into multiple conductive patterns (first, second, third, and fourth coils) arranged in a specific configuration. Each coil generates a magnetic field component, and their combined effect creates a more balanced overall magnetic field, enabling accurate foreign object detection while maintaining reasonable structural complexity.
2Adaptability or versatility
If current applied to the conductive pattern varies due to system power source variation, then the system is adaptable to power fluctuations, but the magnetic field becomes unbalanced and induced voltage varies regardless of foreign object presence
Solution Approach 1:
The system measures the induced voltage in the detection coil and compares it against expected values. When power source variations cause deviations, the system can detect these changes and distinguish them from foreign object-induced changes, maintaining measurement precision through active monitoring and compensation.
Solution Approach 2:
The conductive patterns are arranged with specific asymmetric positioning (first and second coils on one side, third and fourth on the other) with different winding directions. This asymmetric configuration creates complementary magnetic field patterns that balance each other out, reducing the impact of power variations on overall field balance.
3Reliability
If a detection coil is added for foreign object detection, then foreign object detection capability is improved, but the device complexity increases
Solution Approach 1:
The conductive patterns serve dual functions: they generate the magnetic field necessary for wireless power transmission and simultaneously act as detection coils for foreign object detection. This multi-functionality eliminates the need for separate dedicated detection coils, maintaining reliability while controlling device complexity.
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 significantly improves the signal-to-noise ratio of induced voltage variations, increasing the accuracy of foreign object detection and preventing false positives, thereby ensuring safer wireless charging operations.
Implementation Method 1
an induced voltage (or induced electromotive force) may be generated in the detection coil by the generated magnetic field
Implementation Method 2
a current is induced or resonated in the receiving side according to a change in the magnetic field, thereby generating energy
Data Source
AI summary
A detection coil includes a first sub coil disposed on a first PCB, the first sub coil includes a first part, and a second part that is disposed under the first part and that includes: one end connected to one end of the first part and is wound in a direction opposite to a direction the first part is wound. The detection coil includes a second sub coil disposed on a second PCB and including a third part and a fourth part disposed under the third part. The fourth part includes one end connected to one end of the third part, and is wound in a direction opposite to a direction the third part is wound. The first and second parts have polygonal shapes symmetrical to each other. The third and fourth parts have polygonal shapes symmetrical to each other. The first and second sub coils are arranged to partially overlap each other.