Metallic Foreign Object Detector Resonance Noise Suppression
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Solution Overview
Problem
Existing wireless power transmission systems face challenges in accurately detecting metallic foreign objects during power feeding due to resonance and switching noise, which degrade detection accuracy and require additional components or suspend power feeding.
Innovation Solution
A metallic foreign object detector using an antenna coil, capacitor, and control circuit that applies a voltage signal to generate a vibration signal, determining object presence based on waveform analysis, and employing switches to control resonance circuit formation, preventing resonance due to magnetic flux or switching noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If power feeding is performed using a feeding coil and receiving coil, then wireless power transmission is achieved, but resonance due to magnetic flux or switching noise degrades the detection accuracy of metallic foreign objects
Solution Approach 1:
The patent applies preliminary action by performing foreign object detection at specific timing (when no power is fed to the transmission coil) before power feeding begins. This timing selection prevents resonance and switching noise from interfering with detection, thereby maintaining high detection accuracy while enabling reliable wireless power transmission.
2Reliability
If power feeding is suspended for foreign object detection, then detection accuracy is maintained, but charging time increases
Solution Approach 1:
The patent implements periodic action by performing foreign object detection at periodic intervals during the wireless power transmission process. Specifically, detection is performed at timing when power feeding is not active (e.g., during intervals between power transmission cycles), allowing continuous monitoring without permanently suspending power feeding, thus balancing detection accuracy with charging efficiency.
3Productivity
If temperature sensor is used for foreign object detection during power feeding, then detection is possible without suspending power, but device size and cost increase
Solution Approach 1:
The patent applies self-service by using the existing antenna coil to perform both wireless power transmission and foreign object detection functions. By utilizing the antenna coil's resonance characteristics and Q-value changes, the system achieves foreign object detection capability without requiring additional temperature sensors or other external detection devices, thereby maintaining compact device size and low cost while enabling continuous monitoring during power feeding.
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 maintains detection accuracy during power feeding without the need for additional sensors, reducing device size and cost, and avoids suspending power feeding, thus minimizing charging time.
Implementation Method 1
a capacitor that constitutes a resonance circuit together with the antenna coil; a drive part that applies voltage to the resonance circuit to generate a vibration signal in the resonance circuit
Implementation Method 2
When a metallic foreign object enters between the magnetically coupled feeding coil and receiving coil, an eddy current flows in the metallic foreign object by magnetic flux, resulting in heat generation in the metallic foreign object
Implementation Method 3
The electromagnetic induction system, which is already widely known, can perform power feeding with high efficiency due to a high coupling degree between a power transmitting device for feeding power and a power receiving device for receiving power
Data Source
AI summary
An object of the present invention is to suppress deterioration in detection accuracy during power feeding in the detection of the metallic foreign object using the antenna coil. A metallic foreign object detector includes: an antenna coil; a capacitor that constitutes a resonance circuit RC together with the antenna coil; a power supply that applies voltage to the resonance circuit to generate a vibration signal in the resonance circuit; a determination circuit that determines the presence/absence of a metallic foreign object based on the waveform of the vibration signal; a resonance capacitor switch inserted into the resonance circuit; and a control circuit that controls the open/close state of the resonance capacitor switch. The control circuit brings the resonance capacitor switch into a closed state responding to the power supply starting application of voltage to the resonance circuit.