Growing datacenter power demands are driving server equipment manufacturers to achieve higher power conversion efficiencies in order to reduce the thermal footprint of these systems. The transition from a 12 V power distribution bus to a 48 V bus creates the need for a high efficiency, small footprint step down converter (i.e. 48 V – 12 V). This paper presents a practical methodology for designing one of these step-down converters to achieve high efficiency and minimum foot print. The LLC converter will be used as the topology for this design due to the ease with which it achieves zero voltage switching (ZVS) over a wide load range. The paper focuses on a detailed discussion of FET loss, core loss, winding loss, and size minimization. A 1 MHz, 1 kW 1/8 brick form-factor hardware prototype will be presented based on the method discussed, with a power stage efficiency over 98 %.
