Wireless Power Coil EMI Suppression Using an Eddy Current Damper
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Solution Overview
Problem
Existing wireless charging devices suffer from significant electromagnetic interference (EMI) due to the direct connection of power conversion circuit modules to high-frequency AC transmission lines, leading to heat generation and inefficiencies, which current shielding solutions fail to effectively address.
Innovation Solution
A wireless power transfer device with an eddy current damper (ECD) and a high-frequency power cable featuring a distributed inductance-capacitance low-pass filter, which increases impedance and suppresses EMI by stabilizing the electric potential of the wireless power transfer coil group assembly and filtering out high-frequency noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a high-frequency AC transmission line is used to connect the power conversion circuit module to the transfer coil, then the heat generation in the wireless charging range is reduced, but serious electromagnetic interference (EMI) occurs due to unsuppressed harmonics and switching noise
Solution Approach 1:
An eddy current damper (ECD) is introduced as an intermediary component between the power conversion circuit module and the transfer coil. The ECD is electrically connected to the high-frequency AC transmission line and forms an eddy current loss path that suppresses high-frequency harmonics and switching noise, thereby reducing EMI while allowing the transmission line configuration to remain for heat management
Solution Approach 2:
The impedance characteristics of the transmission path are modified by adding the eddy current damper. The damper changes the frequency-dependent impedance profile, creating high attenuation for harmonic frequencies while maintaining power transfer efficiency at the fundamental frequency, thus resolving the EMI issue without sacrificing thermal performance
2Device complexity
If the power conversion circuit module is directly connected to the DC power supply, then the circuit structure is simple, but EMI noise is transmitted to the power supply without filtering
Solution Approach 1:
The eddy current damper serves as a filtering intermediary in the power supply connection path. It is electrically connected between the power conversion circuit module and the DC power supply, providing electromagnetic noise suppression while maintaining the direct connection topology. This adds minimal structural complexity while effectively preventing EMI noise transmission to the power supply
3Object-generated harmful factors
If a shielding layer is added to the high-frequency AC transmission line, then some EMI protection is provided, but the specific implementation and effectiveness of the shielding network is not disclosed
Solution Approach 1:
Instead of implementing a complex multi-layer shielding network with undefined specifications, the solution extracts the essential EMI suppression function and implements it through the eddy current damper. This provides a clear, implementable solution with defined electrical connection requirements, avoiding the ambiguity and complexity of extensive shielding network implementations
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 EMI by increasing high-frequency AC impedance and suppressing harmonics, thereby improving the efficiency and safety of wireless charging by minimizing heat generation and electromagnetic noise.
Implementation Method 1
an eddy current damper (ECD) with a stable electric potential is designed to be electrically connected to a stable electric plane of a power conversion circuit board and to be arranged beside the wireless power transfer coil group to achieve the EMI suppression
Implementation Method 2
a high-frequency power cable featuring a distributed inductance-capacitance low-pass filter, which increases impedance and suppresses EMI by stabilizing the electric potential of the wireless power transfer coil group assembly and filtering out high-frequency noise
Data Source
AI summary
A wireless power transfer device with EMI suppression includes a power conversion circuit board, a wireless power transfer coil group assembly and an eddy current damper (ECD) with a stable potential. The ECD is close to the wireless power transfer coil group assembly and is connected to a low-alternating current (AC) impedance direct current (DC) plane of the power conversion circuit board through a conductor.