EMC Clips for Low-Impedance Noise Dissipation in Vehicle Electronics
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing solutions for directing noise currents away from circuitry in motor vehicle electronic devices are inadequate in meeting EMC limits for radiated immunity and radiated emissions, as they often result in high impedance paths and ineffective noise current dissipation.
Innovation Solution
The use of electromagnetic compatibility (EMC) connectors that directly connect the circuitry to the bottom portion of the housing, providing a low impedance path for noise currents to travel to the electronic ground, thereby reducing interference and radiation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If screws are used to direct noise currents to the bottom of the housing, then the circuit board is fixed to the housing, but the number of screws is limited by physical constraints of the circuit board and noise current dissipation is insufficient
Solution Approach 1:
The invention divides the noise current dissipation function into multiple segments by using both screws (for mechanical fixation and some EMI grounding) and EMC clips (for dedicated EMI grounding at multiple locations). This segmentation allows each component to perform its specialized function without compromising the other, thereby improving noise current dissipation effectiveness without proportionally increasing device complexity.
Solution Approach 2:
The EMC clips serve as intermediary elements that provide additional noise current paths from the circuit board to the housing. These clips act as mediators between the circuit board ground and the housing, creating low-impedance paths that complement the screw-based grounding system and improve overall noise current dissipation.
2Reliability
If EMC springs are used to direct noise currents to the top of the housing, then noise currents can be directed away from circuitry, but the current path is relatively long and impedance is relatively high
Solution Approach 1:
Instead of directing noise currents upward to the top of the housing (as done with EMC springs), the invention inverts the approach by using EMC clips to direct noise currents downward to the bottom of the housing. This inversion creates shorter current paths and lower impedance, thereby improving noise current direction effectiveness while reducing the harmful impedance effect.
Solution Approach 2:
The EMC clips are strategically positioned at specific locations on the circuit board where noise currents are most problematic. This local quality approach ensures that noise current dissipation is optimized at critical locations rather than using a uniform distribution of grounding elements, thereby achieving effective noise current direction with lower overall impedance.
3Reliability
If multiple screws are added to improve noise current dissipation, then more noise current paths are available, but the physical limitations of the circuit board prevent sufficient screw placement
Solution Approach 1:
The invention uses EMC clips as additional copies of the grounding function provided by screws. Rather than relying solely on screws to provide both mechanical support and EMI grounding, the EMC clips are added as supplementary grounding elements that can be placed in locations optimized for EMI performance without being constrained by the same physical limitations as screw placement.
4Device complexity
If the number of screws and EMC springs is reduced, then device complexity is lowered, but EMC limits for radiated immunity and radiated emissions may not be met
Solution Approach 1:
The screws are designed to perform multiple functions: mechanical fixation of the circuit board to the housing and partial EMI grounding. The EMC clips are added specifically to handle the EMI grounding function at optimized locations. This multi-functionality assignment allows the system to meet EMC limits with a reduced total number of components compared to using only single-function elements.
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 reduces noise on the circuitry and radiation into the space, improving the performance and compliance with radiation regulations by providing a shorter, lower impedance path for noise currents to the ground, potentially allowing for a reduction in the number of screws and EMC springs, and enhancing the overall efficiency of electronic devices.
Implementation Method 1
a first noise impedance from the given location to the bottom portion of the housing through the plurality of electromagnetic compatibility connectors is less than a second noise impedance from the given location to other locations of the circuitry
Data Source
AI summary
An apparatus for a vehicle includes an electronic device and an ECU. The electronic device includes a conductive housing that comprises a bottom portion, a PCB that comprises a top layer having circuitry, and a ground layer, the PCB located in the housing, a ground component electronically connected to the ECU and the bottom portion, at least one leg that extends through the PCB and fixes the PCB to the bottom portion, and EMC connectors that connect the circuitry to the bottom portion. At a noise frequency, when there is a noise current at a given location of the circuitry, a first noise impedance from the location to the bottom portion through the EMC connectors is less than a second noise impedance from the location to other locations of the circuitry, and less than a third noise impedance from the location to the bottom portion through the leg.