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

In the standby stage of a server power supply, the flyback converter has been widely used due to its simple structure and low cost. However, since the flyback converter suffers from high-voltage stress and a large transformer, it degrades the efficiency and power density of the server power supply. To relieve these drawbacks, this paper proposes a new standby structure where a flyback converter is integrated with a boost power-factor-correction (PFC) converter. The proposed standby structure can relieve the high-voltage stress and eliminate the large transformer of the conventional flyback converter because the primary side of the flyback converter is merged with the boost PFC converter. Thus, the proposed structure can achieve high efficiency and high power density in the standby stage. Furthermore, it can help the boost PFC converter achieve a soft switching operation, which results in a high-efficiency PFC stage. As a result, the proposed structure improves the overall efficiency and power density of the server power supply. The validity of the proposed structure is confirmed by a prototype with 100-240 V-rms ac input, 750-W PFC output, and 12-V/2-A standby output.