Wireless Power Coil Unit Parasitic Capacitance Balancing
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Solution Overview
Problem
Wireless power transmission technologies using resonance phenomena face issues with high voltage induction on metal parts due to parasitic capacitance, which can lead to electromagnetic interference and inefficiencies in power transmission.
Innovation Solution
A coil unit design that includes a power transmission coil with a first reactance circuit connected to one end and a first adjustment capacitor connected between the other end and the metal part, combined with a second adjustment capacitor connected to the end of a multi-layer coil farthest from the metal part, to reduce parasitic capacitance variations and voltage differences, thereby minimizing high voltage induction on the metal part.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If a reactance circuit for generating resonance is connected to one end portion of the winding of the power transmission coil, then the distance between power transmitting and receiving sides can be increased, but a potential difference develops between the starting edge and end edge of the winding, generating high induced voltage on the metal part
Solution Approach 1:
A first adjustment capacitor is introduced as an intermediary component connected between the end portion of the winding and the metal part. This capacitor mediates the voltage distribution by providing an additional current path that balances the potential difference, thereby reducing the high induced voltage on the metal part while maintaining the resonance-based wireless power transmission function
Solution Approach 2:
The invention changes the electrical parameters of the system by adding the first adjustment capacitor with a specific capacitance value. This parameter modification alters the voltage distribution across the winding and metal part interface, reducing the harmful induced voltage while preserving the resonant coupling that enables extended transmission distance
2Strength
If the power transmission coil is constructed as a multi-layer coil to improve inductance value, then the inductance value can be improved, but variations occur in parasitic capacitance between the windings of individual layers and the metal part
Solution Approach 1:
A second adjustment capacitor is introduced as an intermediary component connected to the end portion of the winding in the layer farthest from the metal part. This capacitor serves as a mediator that compensates for the variations in parasitic capacitance between different layers and the metal part, stabilizing the overall electrical characteristics while maintaining the high inductance value provided by the multi-layer structure
Solution Approach 2:
The invention modifies the electrical parameters by adding the second adjustment capacitor, which compensates for the parasitic capacitance variations inherent in multi-layer coil structures. This parameter change ensures stable performance across different operating conditions while preserving the enhanced inductance value that enables efficient power transmission
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
The solution effectively reduces high voltage induced on metal parts, improving the inductance value of the coil and enhancing the efficiency of wireless power transmission while minimizing electromagnetic interference.
Implementation Method 1
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
Implementation Method 2
a first adjustment capacitor connected between another end portion of the winding of the power transmission coil and the metal part
Implementation Method 3
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 4
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 5
a large current needs to be passed through the power transmitting coil, leading to an increase in leakage flux. This may cause adverse effects on nearby electronics, such as electromagnetic interference
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 are capable of reducing high voltage induced on the metal part. A coil unit Lu1 includes a power transmission coil L1, a first reactance circuit X10 that is connected to one end portion of the winding of the power transmission coil L1 and forms a resonant circuit together with the power transmission coil L1, a metal part SD disposed on the same side as the back side of the power transmission coil L1, and a first adjustment capacitor C10 connected between the other end portion of the winding of the power transmission coil L1 and the metal part SD.