Zichao Ye with advisor Prof. Robert Pilawa-Podgurski
Data centers continue to consume a huge amount of energy as the demands of information processing continuously increases. Therefore, the performance improvement in power conversion (especially of the low-voltage stages) can have large benefits. A good candidate for this performance-driven application is the hybrid switched-capacitor (SC) converter, which uses both capacitors and inductors in the power transfer process. In addition to the benefit of traditional SC converters (i.e., efficient switch utilization, higher capacitor energy density), the additional inductor in hybrid SC converters can help eliminate the capacitor charge-sharing loss, through an operation called soft-charging. Without sacrificing efficiency, capacitor and inductor values can be selected to achieve a minimal passive component volume, which can be significantly smaller than that of a conventional SC or a magnetic-based converter.
In this work, funded by POETS, a 36-60 V input, 4:1 fixed ratio, non-isolated bus converter is designed and implemented using two cascaded 2:1 hybrid SC converters. The prototype (shown in Figure 30) has a total box volume of 0.275 in3, and has been tested with up to 40 A output current (leading to an ultra-high power density of 2180 W in3). Furthermore, the prototype’s efficiency has a peak of 99% and maintains above 98% over a majority of the full load range. This is significantly higher than the state-of-the-art.