High density Hybrid Switched Capacitor Sigma Converter for Data Center Applications

The 48 V bus architecture has become a wide-spread standard in modern Data Centers, due to the increasing power demands of digital loads. This trend demands low-profile, high-density server board solutions able to efficiently step down the input distribution bus to the digital rails. Intermediate Bus Converters (IBCs) are required to step-down the 48 V input voltage for the VRM: this stage is facing an always-decreasing core voltage, and benefits from lower intermediate voltage in terms of efficiency and device reliability. In this scenario, high-step-down solutions with regulation capability could become the best choice for the IBC, being able to provide a stable rail for the VRM. In this paper, a novel regulated Hybrid Switched Capacitor Sigma converter is proposed for this purpose. This new architecture features the Sigma connection of a high-efficiency, non-isolated converter (HSC) with a buck converter. With this approach, high-step down and regulation can coexist with high efficiency and power density, as shown with a 750 W, 8 ^th brick module providing a regulated 5.1 V output with high bandwidth.