Enabling Next-Generation Power Conversion: Design, Dynamic Characterization, and Application of Gallium Nitride Bidirectional Switches

Wang, Guangyu (2025) Enabling Next-Generation Power Conversion: Design, Dynamic Characterization, and Application of Gallium Nitride Bidirectional Switches PhD thesis, University of Liverpool.

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Abstract

The global energy transition towards renewables and the proliferation of electrified transportation are driving an unprecedented demand for power conversion systems that achieve ultra-high power density, high reliability, and bidirectional power flow. Wide band gap (WBG) semiconductors, particularly Gallium Nitride (GaN), offer a pathway to this goal. Among them, the monolithic bidirectional switch (BiS) is recognized as a pivotal component capable of revolutionizing converter topologies by simplifying circuitry and minimizing parasitic elements. However, the development and adoption of GaN-based BiSs are critically hindered by a triad of intertwined challenges: a scarcity of mature and optimized device structures, a complete absence of standardized methodologies for characterizing their dynamic performance, and a lack of system-level topologies designed to exploit their unique advantages fully. Motivated by this pressing need, this thesis presents a holistic research endeavor that systematically bridges the gap from device conception to system-level validation. The research begins with a comprehensive review, which serves to diagnose the technological landscape and explicitly identifies a critical void in the domain of dynamic testing and safe operating area (SOA) definition for BiSs. Guided directly by these insights, the core of this work delivers three interconnected contributions. First, a novel dual-gate GaN BiS structure is proposed. Its operational feasibility, including exceptional symmetry and robust bidirectional conduction and blocking capabilities, is rigorously established through detailed theoretical analysis and Technology Computer-Aided Design (TCAD) simulation, demonstrating superior performance metrics compared to existing designs. Second, a pioneering dynamic test platform is conceived and developed specifically for bidirectional devices. This custom-built system, which incorporates a novel bidirectional clamp circuit and a pulse-test prototype, enables the precise, nanosecond-scale extraction of dynamic on-state resistance (Ron). Utilizing this platform, one of the first systematic empirical definitions of the hard-switching SOA for both combined GaN BiS and the commercial NV6428 BiS is presented. Furthermore, a key device optimization strategy that an optimal gate-driving configuration which can significantly reduces dynamic Ron and enhances operational lifetime. Third, the practical value of the developed BiS is demonstrated through the design and implementation of two distinct, high-density converter topologies: a simplified bidirectional two-port inverter and a highly integrated three-port converter. By using the bidirectional switch NV6428, the two-port inverter achieves a 40% reduction in switch count and an approximate 30% increase in power density over conventional designs. Evolved from it, the three-port converter integrates an additional DC port with minimal added complexity, requiring only two extra inductors while maintaining simple control and demonstrating superior reliability across its entire operating range, as confirmed by comprehensive reliability analysis. The feasibility and performance of the proposed BiS, the test platform, and the converter topologies are conclusively validated through a combination of simulation and experimental prototyping. This thesis, therefore, provides a complete solution stack, comprising a new device, the essential tools for its qualification, and the blueprints for its application, thereby establishing a foundational framework for the future development and deployment of GaN BiSs in next-generation power electronic systems.

Item Type:	Thesis (PhD)
Uncontrolled Keywords:	Bidirectional Switch, GaN, Safe Operating Area, Dynamic Characterization, Three Port Photovoltaic Energy Storage Converter, Reliability
Divisions:	Faculty of Science & Engineering Faculty of Science & Engineering > School of Engineering Faculty of Science & Engineering > School of Engineering > Electrical Engineering and Electronics
Depositing User:	Symplectic Admin
Date Deposited:	11 Feb 2026 10:16
Last Modified:	11 Feb 2026 10:23
DOI:	10.17638/03195421
Supervisors:	Wen, Huiqing Liu, Wen Zhou, Jiafeng
URI:	https://livrepository.liverpool.ac.uk/id/eprint/3195421
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