Inverter Power Semiconductor Layout for EMI Reduction
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Solution Overview
Problem
Electrical assemblies used to convert DC voltage to AC voltage generate significant electromagnetic interference, affecting radio reception and potentially disturbing safety systems in vehicles due to high-frequency emissions.
Innovation Solution
The design includes a first and second supply voltage area for power semiconductors, with the second supply voltage area extending on the side facing away from the input connection and an additional substrate for routing the supply voltage below the power semiconductor, along with symmetrical and low-inductance connections to reduce parasitic capacitance and interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If power semiconductors are operated at high switching speeds to generate AC voltage, then the AC voltage generation efficiency is improved, but electromagnetic interference increases
Solution Approach 1:
The circuit board is divided into separate first and second supply voltage areas with distinct ground connections. This segmentation isolates the high-frequency switching circuits into specific zones, preventing electromagnetic interference from affecting the entire circuit board uniformly, thus maintaining high switching speeds while reducing overall EMI.
Solution Approach 2:
Different areas of the circuit board are assigned different ground connection characteristics. The first supply voltage area has its ground connection optimized for the first power semiconductor, while the second supply voltage area has its ground connection optimized for the second power semiconductor. This local optimization allows each area to handle high-frequency switching without interfering with the other, preserving productivity while reducing EMI.
2Reliability
If supply voltage areas are extended below power semiconductors for shielding, then electromagnetic compatibility is improved, but device complexity increases
Solution Approach 1:
The supply voltage areas serve dual functions: they distribute power to the power semiconductors and simultaneously provide electromagnetic shielding by extending below the semiconductors. This merging of power distribution and shielding functions into a single structural element achieves improved EMC without adding separate shielding components, thus avoiding increased device complexity.
Solution Approach 2:
The supply voltage areas are designed to perform multiple functions: electrical power distribution, ground reference provision, and electromagnetic shielding. This multi-functionality allows the same circuit board features to address both power delivery and EMC requirements, improving reliability without proportionally increasing device complexity.
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 configuration minimizes electromagnetic interference by providing additional shielding and reducing parasitic capacitance, enhancing electromagnetic compatibility and reducing noise from high switching frequencies.
Implementation Method 1
the second supply voltage area also extends on the side of the second power semiconductor which is remote from the input voltage connection and thus below it. This can cause the second supply voltage surface to also extend between the output connection of the second power semiconductor and other metal surfaces of the electrical assembly, for example cooling plates or the like, which can thus develop a shielding effect with respect to other metal objects.
Implementation Method 2
This can be particularly advantageous if the output connection is on the side of the power semiconductor that faces the other components to be shielded, since the capacitance between the output connection and the other metallic components would then be particularly large. This, in combination with the high frequencies that occur due to the switched voltage at the output terminal of the power semiconductor, would be a potential source of interference that could introduce interference into the surrounding systems.
Data Source
Figure 1
Figure 2~3
Figure 4~5
AI summary
Embodiments relate to an electrical assembly (1) for converting a direct voltage into an alternating voltage, which has a first supply voltage surface (10) for distributing a first direct supply voltage and a second supply voltage surface (12) for distributing a second direct supply voltage. The electrical assembly (1) comprises at least one first power semiconductor (24), which has an input connection connected to the first supply voltage surface (12) and an output connection (28) connected to an alternating voltage output (20a) of the assembly. The electrical assembly (1) also comprises at least one second power semiconductor (26), which has an input connection (32) connected to the second supply voltage surface (12) and an output connection connected to the alternating voltage output (20a) of the assembly, wherein the first supply voltage surface (10) extends on the side of the first power semiconductor (24) facing the input voltage connection of the first power semiconductor (24). Furthermore, the second supply voltage surface (12) extends on the side of the second power semiconductor (26) facing away from the input voltage connection (32) of the second power semiconductor (26).