THESIS
2016
xiv, 88 pages : illustrations ; 30 cm
Abstract
Silicon-based power devices have dominated the market of power switches for the past
six decades. Undoubtedly, the trend towards higher efficiency, higher power density and
higher switching frequency continues in power electronics applications. Although there have
been tremendous improvements on silicon (Si) devices, their performance is inevitably
limited by the properties of the Si material, and it is tough to overcome the gap between the
performance demanded and the performance delivered. In recent years, researchers have
focused on wide-bandgap semiconductor materials such as gallium nitride (GaN). Among
various GaN transistors, the enhancement-mode gallium nitride-on-silicon (GaN-on-Si) high
electron mobility transistors, commonly known as e-mode GaN HEMTs, have advantages...[
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Silicon-based power devices have dominated the market of power switches for the past
six decades. Undoubtedly, the trend towards higher efficiency, higher power density and
higher switching frequency continues in power electronics applications. Although there have
been tremendous improvements on silicon (Si) devices, their performance is inevitably
limited by the properties of the Si material, and it is tough to overcome the gap between the
performance demanded and the performance delivered. In recent years, researchers have
focused on wide-bandgap semiconductor materials such as gallium nitride (GaN). Among
various GaN transistors, the enhancement-mode gallium nitride-on-silicon (GaN-on-Si) high
electron mobility transistors, commonly known as e-mode GaN HEMTs, have advantages in
power electronics applications due to their lower manufacturing cost and outstanding parasitic
input and output capacitances. Their higher drain-to-source voltage (V
DS) but lower
on-resistance (R
DS(on)) make them recognized as one of the most promising candidates to
replace silicon in the next generation of power switches. However, due to the differences in
their electrical propertiess of e-mode GaN HEMTs, the driving techniques for Si power
transistors cannot be directly applied to drive e-mode GaN HEMTs.
To tackle the above issues, the target of this research is to explore the techniques of
driving e-mode GaN HEMTs in the MHz-range of switching frequency. First, the
characteristics of e-mode GaN devices are briefly introduced and the merits and design challenges of e-mode GaN HEMT driver circuits are discussed. Second, to optimize the
power efficiency and reliability of GaN-based power applications, a half-bridge gate driver
for e-mode GaN HEMTs with a digital dead-time correction scheme is proposed and
implemented using AMS 0.35μm HV CMOS technology. Third, to reduce ringing due to
switching, PCB layout optimizations for the half-bridge gate driver are analyzed and
incorporated onto the testing board.
To verify the performance of the proposed half-bridge gate driver, an open-loop buck
converter was built. Simulation and experiment results show that the converter with digital
dead-time correction scheme is able to reduce reverse conduction time to below 1 ns. The
power efficiency is improved by approximately 4% compared to the fixed dead-time scheme
in heavy-load condition. In addition, the layout optimization method reduces the overshoot
voltage of the switching node from 100% to below 30%.
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