Electric Field Shield Member for Wireless Power Transfer Noise Suppression
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Solution Overview
Problem
Wireless power transfer systems face challenges in suppressing unwanted radiations from switching circuits and conductor parts while maintaining strong magnetic coupling for efficient power transfer, as existing solutions often compromise magnetic field changes and power efficiency.
Innovation Solution
A wireless power transfer system with a power transmitter device that includes a high-frequency power converter circuit, a power transmitter coil, and an electric field shield member made of conductive materials, which forms an equivalent capacitance with the coil to suppress electric field noise and maintain strong magnetic coupling by ensuring the electric potentials are identical, thereby reducing harmonic noise radiation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If an electrostatic shield is arranged between the stationary part and the first coil to suppress radio waves, then electric field noise is suppressed, but magnetic coupling between coils becomes weaker and power efficiency decreases
Solution Approach 1:
The electric field shield member is designed to maintain equipotential conditions by forming an equivalent capacitance with the power transmitter coil that exceeds the capacitance to earth. This equalizes electric potentials across the shield member, suppressing electric field noise radiation while preventing disruption to the magnetic coupling between coils, thereby maintaining power transfer efficiency.
Solution Approach 2:
The invention changes the key parameter of capacitance configuration by arranging the electric field shield member close to the power transmitter coil to form a specific equivalent capacitance value. This parameter change enables the shield to effectively suppress electric field noise while minimizing impact on magnetic coupling, resolving the contradiction between noise suppression and efficiency.
2Object-generated harmful factors
If the power transmitter device is configured to suppress unwanted radiations, then electric field noise is reduced, but magnetic coupling formed between power transmitter coil and power receiver coil becomes weaker
Solution Approach 1:
The electric field shield member maintains equipotential conditions through its specific capacitance configuration, which suppresses electric field noise without creating potential differences that would disrupt magnetic field distribution. This allows magnetic coupling strength to be preserved while achieving radiation suppression.
Solution Approach 2:
The electric field shield member acts as an intermediary element positioned close to the power transmitter coil. It mediates between the coil and the surrounding space, suppressing unwanted electric field radiation while allowing the magnetic field to pass through and maintain coupling with the receiver coil.
3Loss of energy
If changes in magnetic field of fundamental wave generated from power transmitter coil are maintained at large values, then power transfer efficiency is improved, but electric field noise radiation increases
Solution Approach 1:
The electric field shield member creates equipotential conditions that suppress electric field noise radiation independently of the magnetic field strength. This allows the system to maintain large changes in magnetic field for efficient power transfer while the shield simultaneously suppresses the associated electric field noise through its capacitance-based equipotential mechanism.
Solution Approach 2:
The shield member serves as an intermediary that decouples the relationship between magnetic field strength and electric field noise. It allows strong magnetic field changes to proceed for efficient power transfer while independently suppressing the electric field noise that would otherwise accompany such strong field changes.
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 effectively suppresses electric and magnetic field harmonic noises, enhancing power transfer efficiency and reducing noise levels while maintaining strong magnetic coupling between the transmitter and receiver coils.
Implementation Method 1
the electric field shield member has a structure that uses a conductive member to form an equivalent capacitance between the electric field shield member and the power transmitter coil by electric coupling therebetween
Implementation Method 2
suppresses changes in an electric field in a vicinity of the power transmitter coil, and suppresses radiation of the electric field noise
Implementation Method 3
a power transmitter coil connected to an output of the high frequency power converter circuit
Data Source
AI summary
A wireless power transfer system includes a power transmitter including a high frequency power converter circuit that converts a direct current power into a high frequency power using a switching circuit, a power transmitter coil, and an electric field shield member close to the power transmitter coil and having a structure that uses a conductive member to form an equivalent capacitance between the electric field shield member and the power transmitter coil by electric coupling therebetween during a power transmitting operation such that the value of the equivalent capacitance becomes greater than the value of an equivalent capacitance formed between the power transmitter coil and ground. The power transmitter causes electric potentials in the electric field shield member to be identical using the conductive member, suppresses changes in an electric field in a vicinity of the power transmitter coil, and suppresses radiation of the electric field noise.