Q-Factor Measurement Coil for Foreign Object Detection in Wireless Power
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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 apparatuses, as techniques like those in Patent Documents 1 and 2 struggle to differentiate between the effects of a metallic case and a foreign substance, leading to low precision in 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 waveform response and measures the Q factor to differentiate between the presence of a metallic foreign substance and a metallic case, enhancing precision by eliminating the effect of the metallic case on the Q-factor measurement.
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 based on impedance detection. The detection is achieved by measuring changes in the impedance of the power transmitting coil, which varies when metallic foreign substances are present. This substitution dramatically reduces system cost while maintaining detection capability across wide power supplying ranges.
2Measurement precision
If a temperature sensor is used for detection, then metallic foreign substance detection is enabled, but design restrictions are imposed on equipment due to dependency on thermal conductivity of surroundings
Solution Approach 1:
The patent substitutes thermal-based detection with electrical impedance-based detection. By measuring the impedance changes of the power transmitting coil caused by eddy currents in metallic foreign substances, the system eliminates dependency on thermal conductivity of surrounding materials. This enables versatile application across different equipment designs without imposing thermal management constraints.
3Measurement precision
If existing detection techniques are used, then metallic foreign substance detection is attempted, but precision is low due to inability to differentiate between metallic case effects and foreign substance effects
Solution Approach 1:
The patent segments the detection process into two distinct phases: first measuring the impedance with the metallic case present (baseline measurement), then measuring impedance when a foreign substance is suspected. By comparing these segmented measurements, the system isolates the additional impedance change caused specifically by foreign substances, eliminating false positives from the metallic case.
Solution Approach 2:
The patent utilizes changes in electrical impedance parameters to differentiate between metallic case effects and foreign substance effects. By monitoring impedance magnitude and phase angle variations at the operating frequency, the system can distinguish between the predictable impedance contribution of the metallic case and the anomalous impedance changes indicating foreign substance presence.
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 allows for high-precision detection of metallic foreign substances, reducing the risk of false positives from metallic components in the power receiving apparatus and 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 waveform response and measures the Q factor
Implementation Method 2
a non-contact power transmission system for supplying electric power by adoption of a wireless technique... electromagnetic induction method... magnetic resonance method
Implementation Method 3
When electric power is supplied from a power transmitting side to a power receiving side by adoption of a non-contact technique not limited to the electromagnetic induction method or the magnetic resonance method, a metal may exist between the power transmitting side and the power receiving side. 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.