Standby-Loss Elimination in Server Power Supply

In a server power system, a standby converter is required in order to provide the standby output, monitor the system’s status, and communicate with the server power system. Since these functions are always required, losses from the standby converter are produced even though the system operates in normal mode. For these reasons, the losses deteriorate the total efficiency of the system. In this paper, a new structure is proposed to eliminate the losses from the standby converter of a server power supply. The key feature of the proposed structure is that the main direct current (DC)/DC converter substitutes all of the output power of the standby converter, and the standby converter is turned off in normal mode. With the proposed structure, the losses from the standby converter can be eliminated in normal mode, and this leads to a higher efficiency in overall load conditions. Although the structure has been proposed in the previous work, very important issues such as a steady state analysis, the transient responses, and how to control the standby converter are not discussed. This paper presents these issues further. The feasibility of the proposed structure has been verified with 400 V link voltage, 12 V/62.5 A main output, and a 12 V/2.1 A standby output server power system.