High-frequency-link (HFL) power conversion systems (PCSs) are attracting more and more attentions in academia and industry for high power density, reduced weight, and low noise without compromising efficiency, cost, and reliability. In HFL PCSs, dual-active-bridge (DAB) isolated bidirectional dc-dc converter (IBDC) serves as the core circuit. This paper gives an overview of DAB-IBDC for HFL PCSs. First, the research necessity and development history are introduced. Second, the research subjects about basic characterization, control strategy, soft-switching solution and variant, as well as hardware design and optimization are reviewed and analyzed. On this basis, several typical application schemes of DAB-IBDC for HPL PCSs are presented in a worldwide scope. Finally, design recommendations and future trends are presented. As the core circuit of HFL PCSs, DAB-IBDC has wide prospects. The large-scale practical application of DAB-IBDC for HFL PCSs is expected with the recent advances in solid-state semiconductors, magnetic and capacitive materials, and microelectronic technologies.

Overview of Dual-Active-Bridge Isolated Bidirectional DC–DC Converter for High-Frequency-Link Power-Conversion System

Gallium nitride (GaN) is a compound semiconductor that has tremendous potential to facilitate economic growth in a semiconductor industry that is silicon-based and currently faced with diminishing returns of performance versus cost of investment. At a material level, its high electric field strength and electron mobility have already shown tremendous potential for high frequency communications and photonic applications. Advances in growth on commercially viable large area substrates are now at the point where power conversion applications of GaN are at the cusp of commercialisation. The future for building on the work described here in ways driven by specific challenges emerging from entirely new markets and applications is very exciting. This collection of GaN technology developments is therefore not itself a road map but a valuable collection of global state-of-the-art GaN research that will inform the next phase of the technology as market driven requirements evolve. First generation production devices are igniting large new markets and applications that can only be achieved using the advantages of higher speed, low specific resistivity and low saturation switching transistors. Major investments are being made by industrial companies in a wide variety of markets exploring the use of the technology in new circuit topologies, packaging solutions and system architectures that are required to achieve and optimise the system advantages offered by GaN transistors. It is this momentum that will drive priorities for the next stages of device research gathered here.

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The 2018 GaN power electronics roadmap

Gallium nitride (GaN) power devices are an emerging technology that have only recently become available commercially. This new technology enables the design of converters at higher frequencies and efficiencies than those achievable with conventional Si devices. This paper reviews the characteristics and commercial status of both vertical and lateral GaN power devices, providing the background necessary to understand the significance of these recent developments. In addition, the challenges encountered in GaN-based converter design are considered, such as the consequences of faster switching on gate driver design and board layout. Other issues include the unique reverse conduction behavior, dynamic $R_{\mathrm {{ds}},\mathrm {{on}}}$ , breakdown mechanisms, thermal design, device availability, and reliability qualification. This review will help prepare the reader to effectively design GaN-based converters, as these devices become increasingly available on a commercial scale.

Review of Commercial GaN Power Devices and GaN-Based Converter Design Challenges

This timely second edition has been substantially expanded to keep students and practicing power conversion engineers ahead of the learning curve in GaN technology advancements. Acknowledging that GaN transistors are not one-to-one replacements for the current MOSFET technology, this book serves as a practical guide for understanding basic GaN transistor construction, characteristics, and applications. Included are discussions on the fundamental physics of these power semiconductors, layout and other circuit design considerations, as well as specific application examples demonstrating design techniques when employing GaN devices.

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GaN Transistors for Efficient Power Conversion

Before the emergence of ultra-wideband (UWB) radios, widely used wireless communications were based on sinusoidal carriers, and impulse technologies were employed only in specific applications (e.g. radar). In 2002, the Federal Communication Commission (FCC) allowed unlicensed operation between 3.1–10.6 GHz for UWB communication, using a wideband signal format with a low EIRP level (−41.3dBm/MHz). UWB communication systems then emerged as an alternative to narrowband systems and significant effort in this area has been invested at the regulatory, commercial, and research levels.

IEEE Transactions on Microwave Theory and Techniques and Antennas and Propagation Announce a Joint Special Issue on Ultra-Wideband (UWB) Technology

We present a new normally-off GaN transistor-the tri-gate normally-off GaN metal-insulator-semiconductor field- effect transistor (MISFET). Due to the excellent channel control of a new 3-D gate structure, a breakdown voltage of 565 V has been achieved at a drain leakage current of 0.6 μA/mm and Vgs = 0. The new device has an on/off current ratio of more than eight orders of magnitude and a subthreshold slope of 86 ± 9 mV/decade. The threshold voltage of the new device is 0.80 ± 0.06 V with a maximum drain current of 530 mA/mm. These results confirm the great potential of the tri-gate normally-off GaN-on-Si MISFETs for the next generation of power electronics.

Tri-Gate Normally-Off GaN Power MISFET

In this letter, we present a new technology to increase the breakdown voltage of AlGaN/GaN high-electron-mobility transistors (HEMTs) grown on Si substrates. This new technology is based on the removal of the original Si substrate and subsequent transfer of the AlGaN/GaN HEMT structure to an insulating carrier wafer (e.g., glass or polycrystalline AlN). By applying this new technology to standard AlGaN/GaN HEMTs grown on Si substrate, an AlGaN/GaN HEMT with breakdown voltage above 1500 V and specific on resistance of 5.3 mΩ·cm2 has been achieved.

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High Breakdown ( $> \hbox{1500\ V}$ ) AlGaN/GaN HEMTs by Substrate-Transfer Technology

In this paper we present a new measurement technique for extracting dynamic on-resistance (Rdson) of GaN transistors. Dynamic Rdson of commercial GaN transistors in soft-switching and hard-switching conditions have been measured. By comparing the dynamic Rdson in both switching schemes, it is found that the off-state drain voltage stress is the main cause for the increase of dynamic Rdson, while the switching losses in the hard-switching transient could cause additional trapping and degradation, possibly due to channel hot electrons/phonons.

Extraction of Dynamic On-Resistance in GaN Transistors: Under Soft- and Hard-Switching Conditions

In this letter, we present a new AlGaN/GaN enhancement-mode (E-mode) transistor based on a dual-gate structure. The dual gate allows the transistor to combine an E-mode behavior with low on-resistance and very high breakdown voltage. The device utilizes an integrated gate structure with a short gate controlling the threshold voltage and a long gate supporting the high-voltage drop from the drain. Using this new dual-gate technology, AlGaN/GaN E-mode transistors grown on a Si substrate have demonstrated a high threshold voltage of 2.9 V with a maximum drain current of 434 mA/mm and a specific on-resistance of 4.3 m Ω·cm2 at a breakdown voltage of 643 V.

High-Performance Integrated Dual-Gate AlGaN/GaN Enhancement-Mode Transistor

The PowerChip research program is developing technologies to radically improve the size, integration, and performance of power electronics operating at up to grid-scale voltages (e.g., up to 200V) and low-to-moderate power levels (e.g., up to 50W) and demonstrating the technologies in a high-efficiency light-emitting diode driver, as an example application. This paper presents an overview of the program and of the progress toward meeting the program goals. Key program aspects and progress in advanced nitride power devices and device reliability, integrated high-frequency magnetics and magnetic materials, and high-frequency converter architectures are summarized.

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Bin Lu

Papers

Tri-Gate Normally-Off GaN Power MISFET

High Breakdown ( $> \hbox{1500\ V}$ ) AlGaN/GaN HEMTs by Substrate-Transfer Technology

Extraction of Dynamic On-Resistance in GaN Transistors: Under Soft- and Hard-Switching Conditions

High-Performance Integrated Dual-Gate AlGaN/GaN Enhancement-Mode Transistor

A Technology Overview of the PowerChip Development Program