Switched Tank Converter: Quasi-Resonant Regulation for Soft Start and Mismatch Mitigation Technique

In recent years, there has been a significant increase in the power consumption of data centers. As a result, server rack architecture has shifted from using 12 V to higher voltage levels of 48-60 V. The conventional power delivery system in use involves two stages of dc-dc conversion, utilizing an unregulated first-stage converter followed by a regulated converter. Among the first-stage converter topologies, the 4-to-1 switched tank converter (STC) is highly employed due to its high efficiency and power density. However, the STC has the drawback of generating a large inrush current during the startup phase. To address this issue, typically an auxiliary element such as a buck converter, a hot-swap controller, or an eFuse is employed. Additionally, achieving the zero-current switching condition in both resonant tanks is challenging when a mismatch in the resonant frequencies is considered. This article proposes a novel control technique to mitigate the large inrush that does not involve the use of any additional element, boosting the power density. It also presents a strategy to minimize the mismatch in the resonant frequencies in an STC. The experimental results obtained from a 600-W prototype validate the effectiveness of these approaches.