Sectional Bifilar Filter Layout for HF Harmonic Suppression
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Solution Overview
Problem
Wireless electric vehicle charging systems face challenges in suppressing high-frequency harmonics, which exceed emission limits specified in standards like CISPR and ETSI, necessitating additional harmonics mitigation techniques to achieve regulatory compliance.
Innovation Solution
The implementation of a signal filter with a plurality of laminations forming an annular core, bifilar windings wrapped around separate portions of the core, and the use of nanocrystalline material in the laminations to effectively suppress high-frequency emissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional AC-DC charging systems use an isolation transformer with shielding, then electromagnetic emissions are suppressed, but the system complexity and size increase
Solution Approach 1:
The patent removes the isolation transformer from the wireless power transfer system, extracting the harmful electromagnetic emissions problem from the system architecture. The inherent isolation property of WPT is leveraged, eliminating the need for additional shielding components while maintaining emission suppression.
Solution Approach 2:
The patent introduces a common-mode choke as an intermediary component to suppress high-frequency harmonics. This mediator handles the emissions suppression function that would otherwise require complex transformer-shielding arrangements, simplifying the overall system while achieving the same protective effect.
2Object-affected harmful factors
If a common-mode choke with traditional windings is used, then high-frequency harmonics are suppressed, but core temperature increases due to differential-mode current heating
Solution Approach 1:
The patent segments the core into multiple independent magnetic paths, each handling specific current components. This segmentation allows differential-mode currents to be routed through paths that do not generate harmful leakage flux, reducing core heating while maintaining harmonic suppression effectiveness.
Solution Approach 2:
The patent applies different winding configurations to different sections of the core. The first set of windings handles common-mode currents with high permeability material for effective suppression, while the second set handles differential-mode currents with configurations that minimize core heating, optimizing local performance for each function.
3Object-affected harmful factors
If high permeability material is used in the common-mode choke, then high-frequency harmonics are effectively suppressed, but differential-mode current generates excessive heat
Solution Approach 1:
The patent divides the magnetic circuit into separate paths with different material properties. One path uses high permeability material optimized for common-mode harmonic suppression, while another path is configured to handle differential-mode currents with minimal core loss, preventing excessive heating.
Solution Approach 2:
The patent changes the effective permeability parameter for different current modes by using different winding configurations and core sections. High permeability is utilized for common-mode suppression where beneficial, while the differential-mode path is configured to reduce permeability effects that would cause heating, optimizing energy efficiency.
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 proposed solution effectively mitigates high-frequency harmonics, achieving significant suppression of emissions and reducing core temperature, thereby ensuring compliance with regulatory standards and improving system efficiency.
Implementation Method 1
a plurality of laminations forming an annular core... nanocrystalline material in the laminations to effectively suppress high-frequency emissions
Implementation Method 2
a plurality of laminations forming an annular core... suppress high-frequency emissions
Implementation Method 3
a first bifilar winding wrapped around a first portion of the core, and a second bifilar winding wrapped around a second portion of the core
Data Source
AI summary
A signal filter includes a plurality of laminations forming an annular core, a first bifilar winding wrapped around a first portion of the core, and a second bifilar winding wrapped around a second portion of the core. A wireless power transmitter includes a power input, a power converter coupled to the input and configured to provide high-frequency (HF) current, an output coil, and an output filter between the power converter and the output coil. A wireless power receiver includes an input coil, a power converter coupled to an output and configured to provide current suitable for a load, and an input filter between the input coil and the power converter.