Modular Hybrid Step-Down PFC Converter for Direct AC/DC Conversion with Differential Power Processing in Data Centers

In this work, differential power processing for AC/DC applications has been explored with a switched-capacitor (SC) based hybrid step-down converter. The converter can provide required AC/DC step-down conversions with a high power factor and eliminate intermediate high-voltage DC-link bus and capacitors. Instead, compact low-voltage capacitors are utilized as flying capacitors in the 4-level SC part of the converter that also provides line-frequency distributed energy buffer capability. In order to support higher input AC voltages, the inputs of two converter unit modules are connected in series while their outputs supply two separate loads in an AC/DC differential power processing architecture. This architecture can be used for data centers and telecommunication systems. In this paper, the operation for a single module and multiple modules are verified with a 115VAC-to-48VDC conversion and 200VAC input to two 48VDC outputs, respectively. The experimental results confirm the converter topology, individual operation, and modular operation along with the control method. A single converter achieves 95.8% efficiency at 115VAC-to-48VDC/10A load with a 0.994 power factor.