High Efficiency Isolated Quasi-Resonant Converter for High Step-Up Applications

Resonant converters such as the LLC and SRC can easily achieve high efficiency thanks to their soft-switching features. However, when the converter works to output a high voltage value, the input current will gradually become a very large value with the increase of the power level, which is due to the low input voltage. Since the resonant capacitors and the inductors are placed at the low voltage side, the power loss provoked by them limits the improvement of the efficiency. In this paper, an isolated converter that employs an active quasi-resonant tank is proposed. All the resonant components are located at the secondary side. With smaller current stress for the resonant tank, power loss provoked by the resonant components is very limited in the proposed converter. The correctness of theoretical analysis is verified by a 48V-380V prototype with 500W power level.