Integrated DC Link Capacitor Layout for Low-Inductance Power Modules
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Solution Overview
Problem
Parasitic inductance between electrical power modules and DC link capacitors in traction inverters leads to voltage overshoots and increased switching losses, limiting the efficiency and performance of SiC-based power semiconductors.
Innovation Solution
Integration of the DC link capacitor with the power module using overmolding encapsulation, reducing the distance between the two components and minimizing parasitic inductance, while maintaining high capacitance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the DC link capacitor is placed at a distance from the electrical power module, then it is easier to manufacture and assemble, but parasitic inductance increases leading to voltage overshoots and increased switching losses
Solution Approach 1:
The patent merges the DC link capacitor with the electrical power module into a single integrated unit. The capacitor is positioned inside the power module housing with direct electrical connection to the DC bus bars, eliminating separate mounting and reducing overall system complexity while minimizing parasitic inductance through close proximity integration.
2Reliability
If the DC link capacitor is integrated closer to the electrical power module, then parasitic inductance is reduced and voltage overshoots are minimized, but manufacturing and assembly become more difficult
Solution Approach 1:
The integrated unit is segmented into distinct functional zones: the power module section with semiconductor switches and DC bus bars, and the capacitor section with pre-arranged terminal connections. This segmentation allows each component to be optimized independently while maintaining ease of assembly through modular integration.
Solution Approach 2:
The capacitor terminals are preliminarily positioned and connected to the DC bus bars during capacitor assembly, before the capacitor is installed in the final integrated unit. This preliminary connection arrangement simplifies the final assembly process and ensures proper electrical connections are established without complex manual wiring.
3Reliability
If the DC link capacitor is placed closer to the electrical power module, then voltage overshoots are reduced, but the switching speed is limited by the integrated structure
Solution Approach 1:
The patent applies local quality optimization by creating low-inductance connection paths specifically at the capacitor-to-DC-bus interface. The capacitor terminals are directly connected to the DC bus bars with minimal trace length and optimal geometrical arrangement, providing locally minimized parasitic inductance that enables fast switching while maintaining voltage stability.
Data Source
AI summary
An electrical system includes a power module and a DC link capacitor. The power module includes first and second facing substrates that define between them an inner space of the power module. The power module comprises switches supported by the first or second substrate and extending in the inner space of the power module, and inner electrical conductors extending in the inner space of the power module and connecting the switches. The inner electrical conductors include two inner DC electrical conductors for receiving a DC voltage (E). The DC link capacitor comprises two capacitor electrical conductors facing each other and extending at least partially outside the inner space of the power module and respectively connected to the inner DC electrical conductors for stabilizing the DC voltage (E). The electrical system comprises an overmolding encapsulating at least partially the substrates, the switches, the inner electrical conductors and the capacitor electrical conductors.