A New Standby Structure Integrated with Boost PFC Converter for Server Power Supply

In the standby stage of the server power supply, the flyback converter has been widely used due to its simple structure and low cost. However, it suffers from high voltage stress on the primary switch and large transformer size. Thus, the flyback converter in the standby stage degrades the efficiency and power density of the server power supply. To relieve these drawbacks, this paper presents a new standby structure where the standby stage is integrated with the boost PFC stage. In the proposed standby structure, since the primary side of the flyback converter is integrated into the boost PFC stage, the proposed standby structure can eliminate high voltage stress and large transformer. Furthermore, the proposed standby structure helps the boost PFC stage to achieve soft switching operation. Therefore, the proposed standby structure can improve the efficiency and power density of the server power supply. The validity of the proposed standby structure is confirmed by a prototype with 90-264Vrms AC line, 750W main output, and 12V/2A standby output.