Effect of the heat dissipation system on hard-switching GaN-based power converters for energy conversion

The design of a cooling system is critical in power converters based on wide-bandgap (WBG) semiconductors. The use of gallium nitride enhancement-mode high-electron-mobility transistors (GaN e-HEMTs) is particularly challenging due to their small size and high power capability. In this paper, we model, study and compare the different heat dissipation systems proposed for high power density GaN-based power converters. Two dissipation systems are analysed in detail: bottom-side dissipation using thermal vias and top-side dissipation using different thermal interface materials. The effectiveness of both dissipation techniques is analysed using MATLAB/Simulink and PLECS. Furthermore, the impact of the dissipation system on the parasitic elements of the converter is studied using advanced design systems (ADS). The experimental results of the GaN-based converters show the effectiveness of the analysed heat dissipation systems and how top-side cooled converters have the lowest parasitic inductance among the studied power converters.This work was supported by the Industrial Doctorates Plan of the Secretaria d’Universitats i Recerca del Departament d’Empresa i Coneixement de la Generalitat de Catalunya, the Centro para el Desarrollo Tecnológico Industrial (IDI-20200864), and the Ministerio de Ciencia, Innovación y Universidades of Spain within the project PID2019-111420RB-I00Peer ReviewedPostprint (published version

Characterization and Utilization of 600 V GaN GITs for 4.5 kW Single Phase Inverter Design

Superior properties allow for faster switching and higher power density converters. However, the fast switching capability of GaN, while theoretically beneficial to converter design, presents several challenges due to the presence of printed circuit board (PCB) and device parasitics. Therefore, it is imperative that the results of device characterization reflect actual device behavior in order to adequately model the device for converter design. This thesis focuses on characterization and utilization of 600 V/30 A Gallium Nitride gate injection transistors, or GaN GITs. The experimental data from static and dynamic characterization was used to maximize the performance of the devices in each phase leg of a 4.5 kW, single-phase, full-bridge inverter. The impact of PCB and device parasitics on switching behavior was also investigated, and a trade-off study of switching loss, overshoot voltage, and dead time loss is presented. Device packaging is also of interest regarding the design of high-frequency devices. This thesis compares the impact of two package designs for the GIT device by designing two separate inverters with the same specifications utilizing the different packages. Finally, due to the lower critical energy of the GaN HEMT during a short circuit, this thesis studies the short-circuit robustness of the devices. The performance of a unique gate sensing protection scheme is compared between two different packages, and the impact of the gate drive and protection circuit design parameters on performance is evaluated

Design and Analysis of a Fully-Integrated Resonant Gate Driver

Several decades ago the resonant gate driving technique was proposed. Given the recent rapid growth in GaN HEMT power device applications for high-frequency power applications, research has been conducted in the power electronics field using resonant gate driving for GaN power devices. Previous research for resonant gate drivers for GaN HEMT devices mostly focused on implementing the gate driving function itself, and mostly for normally-on HEMT devices. The normally-off (enhancement mode) GaN power device was introduced to the commercial market in 2009. A new resonate gate driver is proposed in this work to implement resonant gate driving for commercial high-speed normally-off GaN power devices. The desired resonant condition is configured by different turn-on and turn-off driving pulses with specific driving time and pulse width. Using synchronous timing control within the driver integrated circuit, the power device gate voltage is securely clamped within the expected gate voltage at switching frequencies beyond 10 MHz. In this research, a customized resonant gate driver IC was designed and developed on a commercially-available silicon CMOS process. Compared with current commercial gate driver ICs, our test results demonstrate the effectiveness, advantages and limitations of the proposed gate driver IC for the enhancement-mode GaN power device using alternative resonant gate driving techniques for the first time

Multi-objective optimization of power electronic converters

L'abstract è presente nell'allegato / the abstract is in the attachmen

Energy-efficient and Power-dense DC-DC Converters in Data Center and Electric Vehicle Applications Using Wide Bandgap Devices

The ever increasing demands in the energy conversion market propel power converters towards high efficiency and high power density. With fast development of data processing capability in the data center, the server will include more processors, memories, chipsets and hard drives than ever, which requires more efficient and compact power converters. Meanwhile, the energy-efficient and power-dense converters for the electric vehicle also result in longer driving range as well as more passengers and cargo capacities. DC-DC converters are indispensable power stages for both applications. In order to address the efficiency and density requirements of the DC-DC converters in these applications, several related research topics are discussed in this dissertation. For the DC-DC converter in the data center application, a LLC resonant converter based on the newly emerged GaN devices is developed to improve the efficiency over the traditional Si-based converter. The relationship between the critical device parameters and converter loss is established. A new perspective of extra winding loss due to the asymmetrical primary and secondary side current in LLC resonant converter is proposed. The extra winding loss is related to the critical device parameters as well. The GaN device benefits on device loss and transformer winding loss is analyzed. An improved LLC resonant converter design method considering the device loss and transformer winding loss is proposed. For the DC-DC converter in the electric vehicle application, an integrated DC-DC converter that combines the on-board charger DC-DC converter and drivetrain DC-DC converter is developed. The integrated DC-DC converter is considered to operate in different modes. The existing dual active bridge (DAB) DC-DC converter originally designed for the charger is proposed to operate in the drivetrain mode to improve the efficiency at the light load and high voltage step-up ratio conditions of the traditional drivetrain DC-DC converter. Design method and loss model are proposed for the integrated converter in the drivetrain mode. A scaled-down integrated DC-DC converter prototype is developed to verify the design and loss model