LLC Resonant Converter with 99% Efficiency for Data Center Server

The new generation of processors for CPUs, GPUs and AI demand a significantly higher current level of 500A-1000 amperes. To accommodate this significant increase in power demand, the data center server rack must employ a 48V backplane power bus to deliver 25-30KW to its server processor. A state-of-the-art silicon-based power module is demonstrated to offer 96% efficiency and a power density of around 40-50W/in3. In this paper, a wide-bandgap (WBG)-based LLC converter is demonstrated to have greatly improved efficiency and power density. Operating at 500KHz switching frequency, the circuit topology and design practice is a significant departure from the current practice. For example, a complicated transformer structure is broken down into a structure of three simple transformers that can be easily implemented using a form of four-layer printed-circuit-board (PCB). Furthermore, these magnetic components are integrated into a compact structure that is easily manufacturable. By adding two additional shielding layers into the four-layer PCB, a 20db reduction in common-mode noises is realized over the entire frequency spectrum of interest, from 150 KHz up to 30 MHz. Two prototypes of 3kW, 48V DC/DC converters are demonstrated with a peak efficiency of 99% and a power density of 530 W/in3 (33 kW/L).