Novel On-Line Maximum Duty Point Tracking Technique to Improve Two-Stage Server Power Efficiency and Investigation Into Its Impact on Hold-Up Time

The main theme of this paper is to propose a novel on-line maximum duty point tracking (MDPT) technique to improve the efficiency of the server power. The server power consists of a power factor corrector (PFC) and a phase-shift full-bridge (PSFB) converter. The proposed MDPT technique controls the dc-link voltage of the PFC to retain the maximum duty of the PSFB converter, thereby reducing the circulating loss and switching losses of the converter. It will be shown that the overall efficiency can therefore be significantly improved to meet the 80 PLUS Gold code. Moreover, the impact of the proposed MDPT control on the hold-up time is investigated. It will be shown that the dc-link capacitance should be increased in order to give the same hold-up time. The experimental system is set up using a digital signal processor as the digital controller. The specifications of the server power supply include: ac input voltage = 110/220 V, dc output voltage = 12 V, and output power = 480 W. Experimental results show that the efficiency can be improved from light-load to full-load conditions. It will be shown that the efficiency can therefore be improved up to 2.52% to meet the 80 PLUS Gold code. These results confirm the effectiveness of the proposed MDPT technique.