Study on DC/DC converter topology with reduced voltage stress

Abstract

With the recent development of information technology, the markets of power management for telecom, server, and display equipments are gradually increasing. Distributed power architecture (DPA) is popular in these applications for its high performance, efficiency, and reliability. AC/DC front-end converter, the heart of DPA, is under pressures of continuous increasing efficiency and power density. Therefore, technologies need to be continuously developed to fulfill the future requirements. Switching mode power supply (SMPS) consists of passive components, such as inductor and a capacitor, and switching devices, i.e., MOSFET, IGBT, diode and so on. The performances of these semiconductors are highly affected by its voltage rating. In case of MOSFET, the lower voltage rating is, the smaller its on-resistance is. In case of diode, the lower voltage rating is, the smaller the forward voltage drop and the reverse recovery are. Therefore, to improve the power converter efficiency, minimizing the voltage stress on semiconductor is one of the most important design considerations. General power architecture including DPA, which uses AC line as its input source, consists of three stages; (1) power factor correction (PFC) stage to regulate harmonics in the input current; (2) isolated DC/DC stage to provide a galvanic isolation and a stable DC bus voltage or a main output voltage; (3) load converter such as a point-of-load converter (POL) or a voltage regulator module (VRM) to tight regulate the output voltage of each load from the bus voltage. A loosely regulated output voltage of PFC stage, about 400 V, becomes the input voltage of an isolated DC/DC converter and it considerably affects to the voltage stress on the primary side. Similarly, the voltage stress on the secondary side is mainly affected by its output voltage. Especially, an isolated DC/DC stage is given a great deal of weight on volume and efficiency of the total power system. Therefore, careful at...