Soft‐switching DC–DC converter with controllable resonant tank featuring high efficiency and wide voltage gain range

Abstract

A two-mode resonant DC–DC converter with auxiliary switch (named as sLLC-C) has been presented. Two simple structural circuits (namely LLC and LLCC) are integrated into one topology with only two magnetic cores, through the topological transformation method. The proposed converter successfully inherits the advantages of the above two circuits, while avoiding their drawbacks as well. At the rating condition, it functions as an LLC circuit, and thus high conversion efficiency is easily obtained. The LLCC working mode is called automatically once the input voltage increases. In such a way, within a limited frequency range, the voltage gain range is effectively extended. A detailed parameter design is given to help achieve desirable performances. Finally, experiments are carried out to validate the feasibility and correctness of the proposed sLLC-C converter. The output voltage is maintained at 400 V, even if the input voltage varies in the range of 150–400 V. Besides, the preferable soft-switching characteristics are ensured for both the power switches and secondary-side diodes. The maximum efficiency of 97.3% is achieved. Thus, wide voltage gain range and high conversion efficiency are acquired simultaneously. These performances make the proposed converter well appropriate for the fuel cell generation applications.