Novel dual mode operation of phase-shifted full bridge converter to improve efficiency under light load condition

The main theme of this paper is to propose 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 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. An FPGA-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.