PhD Thesis Defense: Phyo Aung Kyaw

Tuesday, October 23, 2018, 10:00am

Rm. 232 Cummings Hall (Jackson Conference Room)

“Efficient Power-Dense Passive Components for Next-Generation High-Frequency Power Conversion”


Advancements in energy systems and electric vehicles have increased demands for efficient and compact power electronics. High-frequency operation is important for improving the power density and miniaturization of switching power converters since it reduces energy storage requirement and improves transient performance. Wide-bandgap semiconductors allows for efficient high-frequency switching, but full realization of their potential in power electronics requires efficient power-dense high-frequency passive components. Magnetic components such as inductors and transformers, due to their frequency-dependent losses, are increasingly the main bottleneck in improving the density of switching power converters.

Although incremental improvements in magnetics, and passives in general, are enabling advances in power electronics, the importance of the problem merits consideration of the fundamental performance limits and exploration of alternative passive component technologies. Analysis of various energy storage mechanisms indicates the potential of mechanical storage coupled with a piezoelectric transduction mechanism. Optimally designed piezoelectric and electromagnetic resonant tanks, in some ideal scenarios, are capable of orders-of-magnitude higher power density than passive components in use today. Investigation of various practical limitations to these ideal scenarios provides insights into possible technological development for improving the performance of passive components and switching converters. This process of assessing the fundamental performance limits, followed by examination of the impact of various practical limitations and experimental verification, also provides a basis for exploring potential passive component technologies and comparing their performance limits with those of electromagnetic passive components.

High-performance resonant tanks and power converters, constructed based on the results from the theoretical analysis, are also presented. First, an integrated LC resonator with a winding made of multiple layers of foil conductors demonstrates a 50% improvement in quality factor over a similar resonator with a single-layer skin-effect limited winding. Second, an optimally designed integrated LC resonant tank, made of commercial Class I ceramic capacitors, has a sub-mΩ effective series resistance and incurs only 4.56 W loss, resulting in a power capability of 7.42 kW in a small 1.14 cm3 volume. The high performance means that a power converter utilizing these prototype resonators will be limited by the performance of switches rather than by the passive component. Finally, a prototype 48 V to 16 V stacked-ladder converter which has a high active device utilization figure of merit, combined with a low-loss small-volume integrated resonant tank, provides a peak efficiency of 97.8% and a high power density of 913 W/in3. The theoretical analysis, together with these prototype resonant tanks and power converter, shows the potential for significant improvement in the efficiency and power density of high-frequency switching converters as well as various technological developments required to achieve such improvements.

Thesis Committee

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