Resonant Circuit Q-Factor Measurement for Foreign Object Detection
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Solution Overview
Problem
Existing non-contact power transmission systems face challenges in precisely detecting metallic foreign substances between the power transmitting and receiving sides, as previous methods struggle to differentiate between the effects of a metallic case and an actual foreign substance, leading to inaccurate detection.
Innovation Solution
A detection apparatus and method utilizing a resonant circuit with a Q-factor measurement coil and capacitors, which applies pulses to detect the Q factor of the resonant circuit, allowing for precise identification of metallic foreign substances by measuring changes in the Q factor and waveform responses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a light sensor or temperature sensor is used to detect metallic foreign substances, then detection capability is provided, but the cost increases significantly when the power supplying range is wide
Solution Approach 1:
The patent replaces expensive light sensors or temperature sensors with an electrical measurement system that uses impedance detection. The detection is achieved by measuring changes in electrical parameters (impedance, current, voltage) of the power transmission system itself, rather than using separate mechanical/optical sensing devices. This substitution dramatically reduces cost while maintaining detection capability across wide power supplying ranges.
Solution Approach 2:
The power transmission system performs self-diagnosis by monitoring its own electrical characteristics. The system uses its existing power transmission components (coils, capacitors, resistors) to detect foreign substances by measuring impedance changes, eliminating the need for separate dedicated detection devices. The system serves both power transmission and detection functions through its existing infrastructure.
2Measurement precision
If a temperature sensor is used to detect metallic foreign substances, then detection capability is provided, but design restrictions are imposed on equipment due to thermal conductivity dependencies
Solution Approach 1:
The patent replaces temperature-based detection with electrical impedance-based detection. By measuring changes in electrical impedance caused by eddy currents in foreign substances, the system avoids all thermal conductivity dependencies and associated design restrictions. This allows greater flexibility in equipment placement, materials, and thermal management designs.
3Loss of energy
If electromagnetic induction method is used for power transmission, then high power transmission efficiency is achieved at short distances, but efficiency deteriorates considerably when distance increases or positioning shifts occur
Solution Approach 1:
The patent employs magnetic resonance technology that operates at specific resonant frequencies to enable efficient power transmission over longer distances and with greater position flexibility. By tuning the resonant frequency of both transmitting and receiving coils, the system achieves high efficiency even when distance increases or positioning shifts occur, overcoming the limitations of conventional electromagnetic induction methods.
4Adaptability or versatility
If magnetic resonance method is used for power transmission, then distance and position flexibility is improved, but the ability to detect metallic foreign substances accurately deteriorates due to interference from metallic cases
Solution Approach 1:
The patent introduces a detection coil separate from the power transmission coils as an intermediary detection element. This dedicated detection coil measures impedance changes specifically related to foreign substances without being affected by the metallic cases of powered devices. The separation of detection function from power transmission function enables accurate foreign substance detection while maintaining magnetic resonance power transmission capabilities.
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 approach enhances the precision of detecting metallic foreign substances, enabling accurate differentiation from metallic components of the power receiving equipment, thus improving the reliability of non-contact power transmission systems.
Implementation Method 1
A detection apparatus and method utilizing a resonant circuit with a Q-factor measurement coil and capacitors, which applies pulses to detect the Q factor of the resonant circuit
Implementation Method 2
The magnetic resonance method is characterized in that, by utilizing a resonance phenomenon deliberately, the magnetic flux shared by the power supplier and the power receiver is small
Implementation Method 3
In this case, an eddy current may flow in the metal so that it is feared that the metal dissipates heat
Data Source
AI summary
Disclosed herein is a detection apparatus including: a resonant circuit provided with a Q-factor measurement coil and one or more capacitors to serve as a circuit for receiving pulses; a response-waveform detecting section configured to detect the waveform of a response output by the resonant circuit in response to the pulses; and a Q-factor measuring section configured to measure a Q factor of the resonant circuit from the response waveform detected by the response-waveform detecting section. It is possible to increase the precision of detection of a metallic foreign substance existing between a power transmitting side and a power receiving side.