With the present ac-voltage distribution system, ac-dc converters are key components for driving many dc voltage applications from the ac grid voltage. There are a lot of electronic devices that natively operate from dc voltage including light emitting diodes (LEDs), personal and laptop computers, and smart phones; for all of them there is a drive to increase functionality and to reduce the volume at the same time. The desire for further miniaturization is, however, facing a dominant obstacle strained by the performance requirements on power electronic circuits.
In this thesis, a design technique for high-performance ac-dc power converters will be presented. A novel grid interface ac-dc conversion architecture and associated circuit implementations are proposed along with novel control methods. This approach simultaneously addresses design challenges associated with high performance (e.g., high efficiency, high power factor, miniaturization, and high reliability/lifetime) of ac-dc power conversion systems. The proposed architecture is suitable for realizing ac-dc converters that switch in the HF range (3-30 MHz) with relatively low-voltage components and with zero-voltage switching (ZVS) conditions, enabling significant converter size reduction while maintaining high efficiency. Moreover, this approach can achieve reasonably high power factor about 0.9, while dynamically buffering twice-line frequency energy using small capacitors operating with large voltage swing over the ac line voltage cycle. The experimental ac-dc converter design demonstrates that excellent combinations of efficiency, power factor, miniaturization can be realized with this approach.
Thesis Supervisor: Prof. David J. Perreault