Switching Control Technique of Phase-Shift-Controlled Full-Bridge Converter to Improve Efficiency Under Light-Load and Standby Conditions Without Additional Auxiliary Components

The main theme of this paper is to propose a switching method to reduce the loss of phase-shift-controlled full-bridge converter under light-load and standby conditions. It will be shown that the efficiency can be improved using the proposed switching control technique. The presented switching control technique controls the full-bridge converter by pulsewidth-modulated (PWM) switching mode under light-load condition and PWM switching with burst mode under standby condition. The transition point between phase-shift switching method and the proposed method is investigated and confirmed by experimental results. A field-programmable-gate- array-based digital-controlled experimental system has been set up. The specifications of the converter include: input voltage=400 V, output voltage=12 V, and output power=400 W. Experimental results show that the efficiency improvement can be up to 26% under light-load condition and the standby power is less than 1 W. These results confirm the effectiveness of the proposed switching control technique.