Optimization of High-Density and High-Efficiency Switched-Tank Converter for Data Center Applications

In this paper, the design methodology of switched-tank converter (STC) is presented. The power loss breakdown analysis is conducted to point out the directions and paths for components optimization. It is revealed that the switching device conduction loss, printed circuit board (PCB) loss, and inductor loss become significant when output power is >150 W. Power loss of four switches is calculated and compared for switching device selection. The resonant capacitor is carefully designed to meet both current stress and ripple requirements. On the other hand, optimal design of the resonant inductors and PCB layout are fully investigated. The core loss model is provided, and different core materials are compared to minimize the core loss. Besides, a fine-tuned inductor winding structure is designed to achieve the lowest winding loss. Furthermore, PCB layout is optimized to get short loop length for each operation state. In addition to the hardware level optimization, an improved control method is proposed, in which the conduction time of switching devices is tuned to mitigate the circulating power. To verify the optimization work, a prototype of STC is built and tested. The experimental results indicate that a state-of-the-art performance of 98.71% efficiency and a 1000 W/in3 high power density is achieved.