Split PCB Electric Field Shield for EMI, Cooling, and FOD
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Solution Overview
Problem
Conventional wireless power transfer systems face challenges in managing electromagnetic interference (EMI) while maintaining effective thermal performance, particularly in automotive applications, where cooling of transmitter and receiver coils is critical, and reliable foreign object detection (FOD) is difficult due to potential heat buildup from undetected foreign objects.
Innovation Solution
A split shield approach using a combination of PCBs with apertures and conductive traces is implemented for both transmitter and receiver coils, allowing air flow for cooling and reducing EMI, while also incorporating eddy current patterns for reliable FOD.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a shield is used to reduce EMI, then electromagnetic interference is reduced, but thermal performance degrades due to blocked air flow
Solution Approach 1:
The shield is segmented into multiple PCB layers with apertures, where the first PCB layer has first apertures and the second PCB layer has second apertures that are offset from the first apertures. This segmentation allows air to pass through both layers while maintaining continuous EMI shielding coverage, resolving the contradiction between EMI reduction and thermal performance.
Solution Approach 2:
The shield incorporates apertures (porous structure) in the PCB layers to allow air flow for cooling while maintaining EMI shielding. The patterned apertures enable thermal management without compromising the electromagnetic interference reduction capability of the shield.
2Object-affected harmful factors
If a shield covers the interface surface, then EMI is reduced, but air flow to coils is blocked
Solution Approach 1:
The shield structure is divided into multiple PCB layers with strategically positioned apertures. The first PCB layer contains first apertures and the second PCB layer contains second apertures offset from the first, creating a segmented pattern that allows air flow paths while maintaining EMI shielding coverage across the interface surface.
Solution Approach 2:
The shield transitions from a single-plane structure to a multi-layer three-dimensional structure. By stacking PCB layers with offset apertures, the design creates vertical air flow paths through the shield structure, enabling cooling functionality while maintaining EMI protection in the horizontal plane.
3Reliability
If foreign object resistance is placed in a corner of the interface surface, then it can escape Q factor and power loss detection, but it is large enough to cause heat
Solution Approach 1:
The shield with its aperture pattern serves as an intermediary structure that enables alternative FOD detection methods. By incorporating eddy current patterns in the shield, the system can detect foreign objects through eddy current effects rather than relying solely on Q factor and power loss measurements, allowing detection of corner-placed objects that would otherwise be undetected.
Solution Approach 2:
The patent replaces the traditional Q factor and power loss detection method with an eddy current-based detection system. The eddy current patterns in the shield provide a different physical mechanism for detecting foreign objects, enabling reliable detection of objects placed in corners where the traditional methods fail.
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 and enhances thermal management, ensuring efficient cooling of coils and reliable FOD, outperforming conventional systems in both EMI reduction and temperature control.
Implementation Method 1
The purpose of the shield is to shield the electric field and let pass of the magnetic field. The electric field shielding reduces the electromagnetic interference (EMI).
Implementation Method 2
the receiver generally includes functions to allow the fan air to cool the receiver
Implementation Method 3
incorporating eddy current patterns for reliable FOD
Data Source
AI summary
A wireless power transfer system is disclosed. The system includes a wireless power transmitter including a transmitter coil and a transmitter electric field shield disposed over the transmitter coil. The transmitter electric field shield includes a first printed circuit board (PCB) and a second PCB. Each of the first and second PCBs includes a number of apertures. The apertures of the first PCB do not overlap with the apertures of the second PCB.