Power Inverter EMI Reduction via Segmented Grounding
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Power inverters in electric vehicles generate significant electromagnetic interference (EMI) due to parasitic inductance between the control circuit ground plane and the case, as well as from high voltage and high amperage switching, which can interfere with vehicle components and pose safety hazards.
Innovation Solution
Minimizing the distance between fasteners securing the circuit board to its base plate and the base plate to the power inverter case, using a single fastener that extends through both, and employing a non-electrical sensing conductor or RFID tags to eliminate EMI from the high voltage interlock system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the control circuit board is mounted to the base plate with multiple fasteners spaced relatively widely apart, then the mechanical stability and electrical connection are achieved, but parasitic inductance increases causing EMI emissions
Solution Approach 1:
The grounding path is segmented into multiple parallel paths by adding additional ground fasteners between the circuit board ground plane and the base plate, reducing the inductance of each individual path while maintaining overall mechanical stability
Solution Approach 2:
The single-point grounding approach is transformed into a distributed multi-point grounding system, creating a two-dimensional array of ground connections that reduces parasitic inductance while maintaining mechanical stability
2Strength
If the base plate is secured to the power inverter case with fasteners spaced relatively widely apart, then the mechanical strength and structural integrity are achieved, but parasitic inductance between ground plane and case increases
Solution Approach 1:
The single grounding path is segmented into multiple parallel grounding paths by adding additional fasteners, reducing the inductance of each path while maintaining the overall structural integrity provided by the distributed fastener pattern
Solution Approach 2:
The mechanical fastening function and electrical grounding function are merged into the same fasteners, allowing the fasteners to serve dual purposes of structural attachment and low-inductance electrical connection
3Measurement precision
If electrical sensing wires are used for the high voltage interlock system, then continuity detection is achieved, but EMI is generated that extends exteriorly from the power inverter
Solution Approach 1:
The electrical sensing wire is replaced with an optical sensing system using optical fibers and optical couplers, substituting electromagnetic field-based detection with light-based detection to eliminate EMI generation while maintaining continuity detection capability
Solution Approach 2:
Optical couplers are introduced as intermediary devices that transmit mechanical connection status information through optical signals rather than electrical signals, eliminating the direct electrical connection that generates EMI
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
Reduces parasitic inductance and subsequent EMI emissions, enhancing EMC noise attenuation and ensuring safe operation by eliminating EMI-induced interference with vehicle systems.
Implementation Method 1
fasteners which electrically connect the circuit board ground plane to the case
Implementation Method 2
an optical coupler completes an optical circuit between the ends of the conductor at the electrical ports
Data Source
Figure 1~3
Figure 4~5
Figure 6~7
AI summary
A power inverter (20) for a hybrid automotive vehicle (100) having a case (22) with an interior and at least one electrical port (26) mounted on the case (22) to electrically connect electrical signals from the interior of the case (22) to an exterior device. A cable connector (28) is associated with each electrical port (26) while a non-electrical sensing conductor (34) extends serially through each electrical port (26) and its associated cable connector (28). A circuit is provided which detects a break in the continuity of the sensing conductor (34) and generates a signal representative of that break in continuity. The non-electrical sensing conductor (34) thus minimizes the emission of EMI from the inverter (20). Additionally, a circuit board (60) is mounted within the interior of the case (22) by fasteners (76) which minimize the spacing between the circuit board (60) and the case (22) to further reduce EMI emissions.