Fixed frequency three-phase CLLC resonant converter for a wide range of voltage outputs

With the rapid development of new energy vehicles, the bidirectional charging technology of vehicle chargers is becoming more and more important, LLC is difficult to achieve a wide range of gain output. In addition, the reverse gain characteristics of LLC are poor. Generally, a wide frequency range is used in LLC resonant converters to achieve a wide range of voltage output, which reduces the efficiency of LLC. In this paper, the structure of three-phase staggered CLLC resonant converter is adopted, and the wide range of voltage output is realized by adjusting the duty cycle at a fixed frequency. The output range of 200-400V is achieved by BUCK circuit with fixed frequency below 400V, and the output range of 400-800V is achieved by BOOST circuit with fixed frequency above 400V. In this paper, an experiment with the output voltage in the range of 240 ~ 800v is set up by simulation, and the feasibility and effectiveness of the scheme are verified.