Novel High Power Density Topologies and Control for the Point-of-Load (POL) Application

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Liu, Tianshu
Power Electronics , POL Converter , DC-DC Converter
High performance microprocessors are promoting the development of modern electronic devices such as smart phones and tablets. These microprocessors have stricter requirement on the power supplies in terms of efficiency and overall size since power supplies are directly affecting performance of microprocessors. These power supplies are directly built right next to loads and they are called Point-of-Load (POL) power supplies. The conventional Buck converter has been the dominant method for implementing non-isolated DC-DC POL power supplies. With the increasing demand to miniaturize the voltage regulators for computers and telecommunication products, high power density POL converter topologies are highly desirable in satisfying this trend. But the difficulty of increasing power density of Buck converter makes Buck no longer to be a good candidate for modern electronic devices. In this thesis, two topologies are proposed to address this issue. First of all, the Asymmetrical Three-Level (ATL) converter is proposed. ATL features reduced voltage and doubled equivalent operating frequency on the inductor compared with the conventional Buck and three level Buck converter. Secondly, the modified Asymmetrical Three-Level (mATL) converter is proposed for the application of high output current. The two-phase mATL converter has reduced voltage and doubled equivalent operating frequency on each inductor compared with the two-phase Buck converter. Also, two interleaved inductor current cancels each other to reduce output current ripple. Finally, the inherent automatic inductor-current sharing mechanism of mATL converter is demonstrated and studied. Also, a new control scheme, Negative Circulating Control (NCC) scheme is proposed to achieve automatic inductor-current sharing in discontinuous conduction mode. Besides, a new control scheme is proposed to extend the output voltage range of mATL converter.
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