T-Type 3-Level Converter Using GaN Midpoint Switches for Part-Load Losses
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Solution Overview
Problem
Existing T-type inverters face high costs and inefficiencies in part-load operations due to the use of wide-bandgap semiconductors like SiC MOSFETs and GaN-based HEMTs, which are thermally inefficient and costly, especially when used in T-branches with high threshold voltages and resistance.
Innovation Solution
A multi-level converter with a T-type circuit topology utilizing monolithic, bidirectional GaN HEMT switches in the T-branch, combined with Si-IGBTs or SiC-MOSFETs in the main branch, to achieve cost-effective and efficient part-load performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If wide-bandgap semiconductors (SiC MOSFETs) are used in T-branch to achieve low conduction losses, then part-load efficiency is improved, but cost and thermal management complexity increase
Solution Approach 1:
The patent changes the material parameter from SiC MOSFET to GaN HEMT, which has fundamentally different electrical characteristics (lower threshold voltage, lower on-resistance). This parameter change enables the T-branch switch to achieve low conduction losses without requiring large device area, thereby reducing thermal stress and simplifying thermal management while maintaining part-load efficiency
Solution Approach 2:
The patent employs a hybrid semiconductor architecture combining GaN HEMT for the T-branch switch with traditional Si-IGBT or SiC-MOSFET for the main branch switches. This composite material approach leverages the advantages of each material: GaN's low loss characteristics for part-load operation and the robustness of Si/SiC for main switching duties, optimizing both efficiency and thermal performance
2Loss of energy
If large-area T-branch made of wide-bandgap semiconductors is designed to reduce conduction losses, then part-load efficiency is improved, but cost increases
Solution Approach 1:
The patent changes the material parameter from SiC MOSFET to GaN HEMT, which has fundamentally different electrical characteristics (lower threshold voltage, lower on-resistance). This parameter change enables the T-branch switch to achieve low conduction losses without requiring large device area, thereby reducing thermal stress and simplifying thermal management while maintaining part-load efficiency
Solution Approach 2:
The patent employs a hybrid semiconductor architecture combining GaN HEMT for the T-branch switch with traditional Si-IGBT or SiC-MOSFET for the main branch switches. This composite material approach leverages the advantages of each material: GaN's low loss characteristics for part-load operation and the robustness of Si/SiC for main switching duties, optimizing both efficiency and thermal performance
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 reduces semiconductor area requirements, lowers costs, and enhances efficiency by leveraging GaN HEMT's low resistance and bidirectional conductivity, particularly under part-load conditions, while maintaining high reliability and reducing thermal stress.
Implementation Method 1
GaN-based HEMTs can also be used in an antiseries connection in the T-branch, since their reverse voltage in the T-branch is sufficient for half the DC link voltage
Data Source
Figure 1~2
Figure 3
AI summary
The invention relates to a multi-level converter (6) with the circuit topology T-type with at least one main branch (7) and at least one T-branch (8), wherein the main branch (7) has several semiconductor switches (T1 to T6) and wherein the T-branch (8) has at least one monolithic, bidirectional, self-conducting semiconductor switch (T7 to T9).