The rack-level 54/48 V bus architecture is an established standard in modern Data Centers, both in classical server applications and accelerator boards. The digital load supply (xPU/ASIC) is almost always provided through a Voltage Regulator Module (VRM), which is a multi-phase buck converter implementing the last stage of the power conversion. With modern technology, Voltage supply for the VRM is at its sweet spot between 6 V and 12 V, enabling the use of wide-spread, commercial power stages. To provide this Voltage rail to the VRM, a first stage connected to the 48 V bus is needed (Intermediate Bus Converter – IBC): as regulation is provided with high performance by the VRM, the IBC can be unregulated to enable very high power density. In this work the Authors present an unregulated, non-isolated 4:1 fixed-ratio Hybrid Switched Capacitor converter called SHSC. Detailed operation is shown, together with experimental results for a 40x18x8 mm discrete implementation providing up to 1.3 kW with a power density of 3.7 kW/in3.
