||Although the overall conversion efficiency of conventional Phase-Shift Full-Bridge Converters (PSFBC) is higher than conventional full-bridge converters, there are some drawbacks on the conventional PSFBCs. The drawbacks might include energy circulation loss, duty cycle loss and low efficiency at light load etc. To improve the overall conversion efficiency of PSFBCs, it is important to effectively and accurately estimate the power loss of PSFBCs. Conventional power-loss estimation of PSFBCs can effectively calculate the power loss conducted at full load; however, it cannot accurately estimate the power loss at light load. Therefore, a new power-loss estimation of PSFBCs including an iterative procedure for power-loss estimation at light load is proposed in this paper to improve the accuracy of conventional power-loss estimation.|
PSFBCs often work under a constant resonant inductor; however, this architecture cannot satisfy the improvement of conversion efficiency at light and full loads at the same time. By the proposed iterative power-loss estimation, the optimal resonant inductor under different load conditions can be obtained. Therefore, a variable resonance inductor which can be controlled automatically under different load conditions to improve the efficiency of PSFBCs is then designed in this thesis. Three inductor values are chosen for the proposed variable resonance inductor to increase the soft switching operation range. The Zero-Voltage Switching (ZVS) can be achieved at the light load and the conduction loss at the full load can also be reduced. Therefore, the overall conversion efficiency of the proposed PSFBC can be improved. A circuit prototype of the proposed PSFBC with specification of rated input voltage 380V, output voltage 48V and 480W is implemented in this thesis. Experimental results show that the proposed PSFBC can adjust the inductor values of variable resonance inductor automatically with respect to different load conditions. The conversion efficiency improvement, about 2.58% at the light load and 1.33% at the full load, can be achieved. The proposed PSFBC is also applied to the battery charger under different State of Charge (SOC). The simulated results show that the about 1.35% charging energy can be saved by the proposed PSFBC.