Wireless Power Coil Unit Reducing Induced Voltage on Metal Parts
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Solution Overview
Problem
Wireless power transmission technologies using resonance face issues with high voltage induction on metal parts due to parasitic capacitance, which can lead to electromagnetic interference and adverse effects on nearby electronics.
Innovation Solution
A coil unit with a power transmission coil and reactance circuits connected to both ends, where the ratio of the second reactance value to the first reactance value is set based on the mean distance between the winding and the metal part, effectively reducing the voltage difference induced on the metal part via parasitic capacitance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a reactance circuit is connected to only one end of the power transmission coil winding to generate resonance, then wireless power transmission using resonance phenomenon is achieved, but a potential difference develops between the starting edge and end edge of the winding, causing high induced voltage on the metal part via parasitic capacitance
Solution Approach 1:
The reactance circuit is divided into two separate reactance circuits (first reactance circuit and second reactance circuit) connected to each end of the winding respectively, rather than connecting a single reactance circuit to one end only. This segmentation allows independent control of voltage at each end, eliminating the potential difference that causes high induced voltage on the metal part.
Solution Approach 2:
The invention changes the parameter configuration by setting specific reactance values for the first and second reactance circuits. The ratio of the second reactance value to the first reactance value is precisely controlled to compensate for the potential difference between the two ends of the winding, thereby reducing the induced voltage on the metal part while maintaining resonance for efficient wireless power transmission.
2Power
If large current is passed through the power transmitting coil for large power transmission, then power transmission capability is improved, but leakage flux increases causing electromagnetic interference on nearby electronics
Solution Approach 1:
The invention converts the harmful leakage flux into a beneficial effect by introducing a metal part (such as a conductive plate) that utilizes the leakage flux to generate eddy currents. These eddy currents create a magnetic field that opposes the original leakage flux, effectively canceling it out. This allows high power transmission through the coil while suppressing electromagnetic interference with nearby electronics.
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 configuration significantly reduces high voltage induction on metal parts, minimizing electromagnetic interference and enhancing the safety and efficiency of wireless power transmission systems.
Implementation Method 1
systems that utilize the resonance (sympathetic resonance) phenomenon are becoming mainstream. Compared with electromagnetic induction, use of the resonance phenomenon has an advantage of allowing the distance between the power transmitting and receiving sides to be increased
Implementation Method 2
The aluminum plate blocks exposure of leakage flux to the outside
Implementation Method 3
a potential difference develops between the starting edge and end edge of the winding of the power transmission coil. Consequently, a high induced voltage to ground is generated on the metal part owing to the developed potential difference via a parasitic capacitance
Data Source
AI summary
A coil unit, a wireless power feeding device, a wireless power receiving device, and a wireless power transmission device are provided that can reduce high induced voltage on the metal part. A coil unit includes a power transmission coil, reactance circuits and that each form a resonant circuit together with the power transmission coil, and a metal part disposed on the same side as the back side of the power transmission coil. A ratio between a first reactance value of the first reactance circuit and a second reactance value of the second reactance circuit is set based on the ratio of the mean distance between the winding and the metal part in a part of the winding from the other end to the central portion to the mean distance between the winding and the metal part in a part of the winding from one end to the central portion.