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

Quasi-regulation and mismatch mitigation technique for switched tank converters

Data center power consumption has been increasing remarkably in the last decades, mainly due to the massive adoption of cloud computing. Due to the vast amount of power consumed, server rack architecture has switched from 12 V to (48 V – 60 V). The commonly used power delivery system employs two stages of DC-DC conversion, cascading an unregulated first-stage converter and a regulated one. The 4-to-1 switched tank converter (STC) is one of the main topologies used as a first stage thanks to its very high efficiency and power density. However, a limitation of the STC is its large inrush current during the startup phase. To avoid this, usually the converter is preceded by a DC-DC converter, a hot-swap controller or an eFuse. Moreover, ensuring the zero current switching condition in both resonant tanks is not straightforward in presence of a mismatch between the resonant frequencies. In this paper, a novel control technique that avoids a large inrush current at startup without the usage of an auxiliary converter and a strategy to minimize the mismatch in the resonant frequencies are proposed for the STC. Experimental results for a 600 W prototype show the validity of these approaches

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