Power Semiconductor Module Layout for Cooler Snubber Capacitors
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Solution Overview
Problem
Existing power semiconductor modules face challenges in achieving high current density while preventing overheating of snubber capacitors due to increased heat dissipation, which can lead to failures.
Innovation Solution
The design includes a snubber capacitor positioned outside the overlapping area of positive and negative electrode terminals, connected through separate bus bars, to reduce heating and wiring inductance, with symmetric placement for balanced current flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a snubber capacitor is mounted on an insulating substrate inside a power semiconductor module, then the wiring inductance decreases and surge voltage is reduced, but the mounting space for switching elements is decreased
Solution Approach 1:
The patent transitions from a 2D planar mounting approach to a 3D spatial arrangement by positioning the snubber capacitor beneath the overlapping region of positive and negative electrode terminals. This vertical placement utilizes the third dimension (depth/height) to accommodate the capacitor without consuming additional planar mounting space, thereby resolving the contradiction between surge voltage reduction and mounting space availability.
Solution Approach 2:
The snubber capacitor is nested within the overlapping area of the electrode terminals, effectively placing one component (capacitor) within the spatial envelope defined by other components (terminals). This nesting approach allows the capacitor to be positioned in a space that would otherwise be occupied by terminal overlap, optimizing the use of available volume without interfering with switching element mounting.
2Productivity
If the rated current and switching speed are increased, then the power semiconductor module achieves high current density and low conduction losses, but the di/dt at turn-off increases causing surge voltage to exceed rated voltage
Solution Approach 1:
The snubber capacitor acts as an intermediary component that mediates between the high di/dt generated by fast switching and the voltage stress on the power semiconductor devices. By providing a localized energy storage element, the capacitor absorbs the voltage spike and limits the surge voltage to within rated voltage, enabling high current density operation without compromising device safety.
Solution Approach 2:
The snubber capacitor provides beforehand cushioning by being pre-positioned and pre-charged to counteract the surge voltage that will occur during turn-off switching. This protective measure is in place before the switching event, cushioning the system against the harmful effects of high di/dt and preventing overvoltage failures.
3Loss of energy
If the positive electrode terminal and negative electrode terminal are disposed to overlap to reduce wiring inductance, then the current flow efficiency improves, but the heat dissipation increases causing the snubber capacitor to overheat
Solution Approach 1:
The patent introduces asymmetry in the thermal management approach by positioning the snubber capacitor specifically beneath the overlapping region rather than distributing it symmetrically. This asymmetric placement strategically locates the capacitor in an area where it can effectively reduce wiring inductance while being thermally isolated from the highest heat generation zones, thus managing the trade-off between energy efficiency and temperature control.
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 enables high current density with reduced snubber capacitor heating, leading to lower losses and improved reliability in power semiconductor modules and motor drive systems.
Implementation Method 1
the wiring inductance of the main circuit decreases for a current flowing through the snubber capacitor at the time of turn-off switching, and thus the surge voltage can be reduced
Implementation Method 2
the positive electrode terminal and the negative electrode terminal are disposed to overlap one another when viewed from a planar direction, and thus magnetic flux due to a current flowing between the positive electrode terminal and the negative electrode terminal can be reduced
Data Source
AI summary
In a power semiconductor module including a snubber capacitor, the power semiconductor module capable of achieving both a high current density and prevention of heating of the snubber capacitor is provided. The power semiconductor module includes: a positive electrode terminal; a negative electrode terminal of which at least a part is disposed to overlap the positive electrode terminal in a plan view; a first wiring branching from the positive electrode terminal; a second wiring branching from the negative electrode terminal; and a snubber capacitor disposed outside of a position at which the positive electrode terminal and the negative terminal overlap each other in the plan view and connected through the first wiring and the second wiring.