Asymmetric half-bridge resonant converter with voltage-lift technique

Abstract

Today, IT industry is constantly growing such as internet and cloud computing service. According to the trends, the data center is expanded in the world and its power consumption is also increased. Therefore, high efficiency of data center is strongly required in order to solve environment problems such as global warming by increasing power consumption of data centers. The new structure ($480V_{AC}-48V_{DC}$) of data center is already presented in order to improve efficiency of data center by reducing the transmission stages. However, the structure requires a change of server power system from AC/DC server power system to DC/DC one. Efficiency of DC/DC server power system is lower than AC/DC server power system because of large conduction losses in primary-side. Because of that, total efficiency of $480V_{AC}-48V_{DC}$ is almost same to the conventional structure. The study of DC/DC server power system for high efficiency is strongly required in order to achieve high total efficiency of $480V_{AC}-48V_{DC}$ structure. Therefore, this paper proposes asymmetric Half-Bridge (HB) resonant converter for high efficiency of DC/DC server power system by using voltage-lift technique. Because the transformer in DC/DC server power system have large turns ratio by higher input voltage and the proposed converter is able to be optimally designed at nominal input voltage by narrow input voltage range, the primary conduction loss is significantly reduced. Because there are no additional switches, large additional loss of the switches can be also removed. Therefore, the proposed converter can be achieved high efficiency. In this paper, the circuit derivation, operation principle, relevant analysis and design example of the proposed converter are presented. Finally, the validity of this study is confirmed by the experimental results of prototype 300W (12V/25A) converters.