Capacitor Busbar Layout for Low-Inductance Power Conversion
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Solution Overview
Problem
The increase in wiring inductance between the capacitor element and the power module unit, leading to elevated temperatures and reduced lifespan due to heat transfer through the busbar, is a significant issue in high-output-density power conversion devices.
Innovation Solution
The power conversion device design includes a capacitor busbar with a flat-plate portion exposed outside the sealing resin, where the element-connection and power-terminal-connection position ranges are equivalent in length and center position, maintaining a sufficient width to reduce electric resistance and suppress wiring inductance, while the busbar's current path is externally exposed for improved heat dissipation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the busbar is designed with a specific portion having smaller thickness to increase electric resistance, then the DC component is guided away from the capacitor element, but the wiring inductance between the capacitor element and power module increases
Solution Approach 1:
The busbar is divided into multiple portions with different thicknesses: a first portion with larger thickness for low inductance current path, and a second portion with smaller thickness for DC component guidance. This segmentation allows the busbar to simultaneously achieve low wiring inductance and effective DC component diversion, resolving the contradiction between capacitor protection and inductance reduction.
2Object-generated harmful factors
If the busbar connects the capacitor element and power module with sufficient width, then the electric resistance is reduced and wiring inductance is suppressed, but heat dissipation becomes insufficient
Solution Approach 1:
Different portions of the busbar are designed with different thicknesses to optimize local functions: the first portion has larger thickness for low resistance and low inductance, while the second portion has smaller thickness for heat dissipation. This local quality differentiation allows the busbar to simultaneously achieve low wiring inductance and effective heat dissipation.
Solution Approach 2:
The busbar design utilizes the thickness dimension (Z-direction) in addition to the planar dimensions to solve the heat dissipation problem. By varying the thickness of different portions, the design achieves both low inductance (through sufficient width) and improved heat dissipation (through reduced thickness in specific areas), effectively addressing the contradiction in three-dimensional space.
3Power
If the power conversion device is designed for high output density, then the power output is increased, but heat generation and heat transfer to the capacitor element are significantly increased
Solution Approach 1:
The busbar is segmented into portions with different thicknesses to manage heat distribution: the first portion with larger thickness handles high current with low resistance, while the second portion with smaller thickness reduces heat transfer to the capacitor element. This segmentation allows high output density to be achieved while controlling heat transfer to sensitive components.
Solution Approach 2:
The busbar acts as an intermediary between the power module and capacitor element, with its varying thickness profile serving as a thermal management mechanism. The thinner second portion functions as a thermal barrier that allows electrical connection while reducing heat transfer to the capacitor element, enabling high power output without excessive heat transfer.
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 design effectively suppresses the increase in wiring inductance and heat generation, thereby protecting the capacitor elements from temperature rise and extending their lifespan, while allowing for efficient heat dissipation and downsizing of the power conversion device.
Implementation Method 1
the busbar connects the capacitor element, the DC power supply, and the power module, and is formed such that a DC path between the DC power supply and the power module is exposed to outside of the sealing resin
Implementation Method 2
the flat-plate portion serving as a current path between the capacitor element and the power module unit, and a current path between the DC power supply and the power module unit, is exposed to outside from the capacitor sealing resin. Thus, heat dissipation of the capacitor busbar can be improved.
Implementation Method 3
heat dissipation of the capacitor busbar can be improved
Implementation Method 4
a capacitor having a capacitor element for smoothing DC voltage supplied from an external DC power supply
Implementation Method 5
a power module having a semiconductor element for performing power conversion
Implementation Method 6
a cooler for cooling the power module
Implementation Method 7
a cooler for cooling the power module
Implementation Method 8
when the temperature of the power module increases, heat transfers from the power module to the capacitor element via the busbar, and the temperature of the capacitor element is also increased by the transferred heat
Data Source
AI summary
This power conversion device includes: a power module unit; and a capacitor module including a capacitor element, and a capacitor busbar. The capacitor busbar has a flat-plate portion, a plurality of power terminal connection portions, a power supply connection portion, and a plurality of element connection portions. An element-connection-portion position range which is a position range in a first direction between two element connection portions located at both ends, and a power-terminal-connection-portion position range which is a position range in the first direction between two power terminal connection portions located at both ends, are within a position range in the first direction where the flat-plate portion is located. A length of the element-connection-portion position range and a length of the power-terminal-connection-portion position range are equivalent to each other. A center position of the element-connection-portion position range and a center position of the power-terminal-connection-portion position range are equivalent to each other.