Power Semiconductor Device Stray Capacitance Balancing
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Solution Overview
Problem
Existing power semiconductor devices face issues with stray capacitance imbalance due to single-sided cooling and long wiring plates, leading to increased noise and parasitic inductance, making them unsuitable for efficient noise reduction.
Innovation Solution
A power semiconductor device design featuring an insulator plate with a first polarity-side surface electrode, an intermediate surface electrode, and an adjusting electrode connected to the heatsink, with a sealing resin or laminated structure between the adjusting electrode and the second polarity-side terminal, to balance stray capacitances and reduce parasitic inductance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a heatsink is used for single-sided cooling, then the device structure is simplified, but stray capacitance imbalance increases causing noise
Solution Approach 1:
The patent applies asymmetry by introducing an adjusting electrode only on the negative polarity side, creating an asymmetric capacitor structure that compensates for the inherent capacitance imbalance caused by single-sided cooling. The adjusting electrode forms a capacitor with the negative polarity terminal, balancing the total stray capacitance between positive and negative sides.
Solution Approach 2:
The patent changes the capacitance parameter by adding the adjusting electrode with specific capacitance value. This electrode modifies the stray capacitance distribution, allowing the negative polarity side capacitance to match the positive polarity side capacitance, thereby reducing noise caused by capacitance imbalance.
2Reliability
If wiring plates are extended to connect terminals, then electrical connection is achieved, but parasitic inductance increases
Solution Approach 1:
The patent reduces parasitic inductance by changing the spatial arrangement of connections. Instead of using long wiring plates extending from terminals, the adjusting electrode is mounted directly on the heatsink surface, creating a compact capacitor structure that minimizes current loop area and thus reduces parasitic inductance.
3Object-affected harmful factors
If additional parts are added to balance stray capacitance, then noise is reduced, but device complexity increases
Solution Approach 1:
The adjusting electrode serves multiple functions: it forms a capacitor to balance stray capacitance, provides a mounting structure on the heatsink, and creates a compact connection that reduces parasitic inductance. This multi-functionality reduces the need for additional separate components.
Solution Approach 2:
The adjusting electrode utilizes the existing heatsink surface and sealing resin structure to form the capacitor, rather than requiring a separate dedicated capacitor component. The heatsink itself becomes part of the capacitance balancing mechanism, 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
The solution effectively reduces parasitic inductance and noise while allowing for single-sided cooling, achieving balanced stray capacitances without additional parts, thus enhancing noise suppression.
Implementation Method 1
a part of the sealing resin or a laminated structure with alternating conductive and dielectric layers is placed between the surface of the adjusting electrode and the second polarity-side terminal
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
A power semiconductor device includes a first polarity-side semiconductor element whose first principal electrode is in contact with a first polarity-side surface electrode on an insulator plate; a second polarity-side semiconductor element whose first principal electrode is in contact with an intermediate surface electrode on the insulator plate; an intermediate conductor connecting the intermediate surface electrode with a second principal electrode of the first polarity-side semiconductor element; a heatsink being in contact with the insulator plate; a sealing resin sealing the first polarity-side semiconductor element, the second polarity-side semiconductor element, the insulator plate, and the intermediate conductor; a second polarity-side terminal of plate-type connected with a second principal electrode of the second polarity-side semiconductor element and extending externally from the sealing resin; and an adjusting electrode mounted and connected to the heatsink so as to have a surface facing the second polarity-side terminal.