Over the past decade computers, displays, smart phones and other consumer electronics systems have become thinner while also becoming more powerful. As a result, the market continues to increase its demand for thinner power supply solutions with greater power density. This article examines the feasibility of adopting various non-isolated dc-dc step-down topologies for an ultra-thin 48 V to 20 V rated to 250 W. It examines the pros and cons of various non-isolated topologies and how the topology impacts the choice of the power transistors and magnetics, specifically the inductors, as these two components account for the bulk of the losses in a converter. The article also undertakes a detailed analysis of the challenges to design thin inductors for these applications, including examining the factors that drive inductor losses, inductor size, and the design tradeoffs, including the impact on EMI. For this work, an ultra-thin multilevel converter topology was selected, built, and tested. The experimental results obtained from this converter were used to further refine the operating setting and component selections that resulted in a peak efficiency exceeding 98%.
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