Sigma Converter Family With Common Ground for the 48 V Data Center

The 48 V bus architecture has become a standard in modern data centers, due to the increasing power demands of digital loads. This requires low-profile, high-density intermediate bus converters, able to efficiently step-down the input bus. Usually, this bus has a wide variation (40–60 V), and the voltage regulation module (VRM) must withstand the whole converted range, with a negative impact on efficiency due to design oversizing. A regulated intermediate bus converter can address this issue, enabling a fine-tuned VRM design. In this article, a novel regulated regulated hybrid switched capacitor (RHSC) sigma converter family is proposed, which enables regulation without sacrificing efficiency or power density. This is enabled by a new architecture featuring the
sigma
connection of a high-efficiency, unregulated converter with a low-power, regulated one sharing the same ground reference potential (GND) domain, i.e., without the need of functional isolation. With this approach, efficiency and regulation can coexist in a single converter. This work includes the full analysis and design tools for the new RHSC family, together with two demonstrators: a 1.2 kW, 48–12 V down-solution and a 750 W, 48–5.1 V eighth-brick module, both exceeding a power density of 1 kW/in
$^{3}$
.