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

Abstract

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 V to 60 V), and the VRM must withstand the whole converted range, with a negative impact on efficiency due to design oversizing. A regulated IBC can address this issue, enabling a fine-tuned VRM design. In this paper, a novel regulated Regulated Hybrid Switched Capacitor sigma converter family (RHSC) is proposed, which enables regulation without sacrificing efficiency or power density. This is enabled by a new architecture featuring the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">sigma</i> connection of a high-efficiency, unregulated converter with a low-power, regulated one sharing the same <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">GND</i> 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 V to 12 V down-solution and a 750 W, 48 V to 5.1 V 8 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$^{th}$</tex-math></inline-formula> brick module, both exceeding a power density of 1 kW/in <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$^{3}$</tex-math></inline-formula> .