A Non-isolated Fixed-ratio DC-DC Converter Using Switched Auto-transformer (SATx) for Data Center Applications

The bus converter is an essential component in the 48 V power delivery architecture for data centers. This paper will present an unregulated, non-isolated DC-DC converter providing fixed-ratio DC voltage conversion. The converter operates at soft-switching and fixed ratio can be any integer larger than 2. The transformer winding voltage is switched in series and parallel alternatively to realize voltage conversion. Comparison with the isolated center-tapped LLC converter is given. Finally, a 1 kW 4:1 prototype is designed, which has a dimension of 23 by 17 by 7.6 mm (5.5 kW/in ³ power density) and reaches a peak efficiency of 97.8% and full-load efficiency of 96.8% at 54 V input voltage.