Bootstrap Capacitor Layout Inside an Intelligent Power Module
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Solution Overview
Problem
Existing inverter devices for three-phase motors require additional space and insulation distances due to the separate placement of bootstrap capacitors and intelligent power modules, leading to increased on-board space usage and potential noise interference.
Innovation Solution
The integration of a bootstrap capacitor on a printed wiring board between the intelligent power module and the printed wiring board, reducing the insulation distance and allowing for high-density component placement while minimizing thermal and noise interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the bootstrap capacitor is placed separately from the intelligent power module, then the insulation distance is increased for safety, but the on-board space usage increases and noise interference occurs
Solution Approach 1:
The patent merges the bootstrap capacitor with the intelligent power module by placing it on the opposite side of the module, integrating two previously separate components into a unified structure. This reduces the overall space occupation while maintaining necessary insulation distances through the module's physical structure.
Solution Approach 2:
The patent transitions from a planar arrangement where the capacitor and module are separate to a three-dimensional configuration where the capacitor is positioned on the opposite side of the module. This vertical stacking approach reduces the footprint area while preserving insulation requirements.
2Reliability
If the bootstrap capacitor is placed separately from the intelligent power module, then the insulation distance is increased for safety, but noise interference occurs
Solution Approach 1:
By integrating the bootstrap capacitor with the intelligent power module in a unified structure, the patent reduces the separation distance while the module's physical structure and grounding design maintain noise isolation. The capacitor is electrically connected to the module's ground terminal, creating a noise reference path that prevents interference.
Solution Approach 2:
The intelligent power module acts as an intermediary structure between the bootstrap capacitor and the external environment. The module's internal grounding system and metal casing serve as a shield, mediating between the high-frequency switching nodes and external noise sources, thereby preventing noise propagation while maintaining compact integration.
3Reliability
If additional insulation structures are added between the bootstrap capacitor and intelligent power module, then the insulation performance is improved, but the device complexity increases
Solution Approach 1:
The patent eliminates the need for separate insulation structures by merging the capacitor with the module. The module's own metal casing and grounding system serve as the insulation barrier, removing the requirement for additional insulating materials or structures while maintaining or improving insulation performance.
Solution Approach 2:
The intelligent power module performs multiple functions: it serves as the power switching device, provides structural support, acts as an electromagnetic shield, and functions as the mounting base for the bootstrap capacitor. This multi-functionality eliminates the need for separate insulation components, reducing overall 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 achieves high-density integration of components, reduces on-board space requirements, and prevents noise interference, enhancing the operational efficiency of the inverter device.
Implementation Method 1
The bootstrap capacitor is charged during an ON operation of the lower arm-side switching element and generates a potential higher than a low potential at the upper arm-side switching element
Data Source
AI summary
To achieve high density integration of components while securing an insulation distance between a bootstrap capacitor and an intelligent power module. In a printed wiring board, a region where a capacitor is mounted is located in a region where an intelligent power module is mounted. Therefore, the capacitor mounted on the printed wiring board is placed between the printed wiring board and the intelligent power module.