Three-phase three-level LC-type series resonant DC/DC converter with variable frequency control

Multi-phase multi-level converter is an optimal alternative for high input and high power system. The voltage stress on the primary switch is only one-nth of the input voltage due to its multi-level structure. The current rating of power devices can be reduced by the multi-phase structure. To achieve soft-switching and improve efficiency, the resonant tank can be introduced to optimize the performance of the converter. In this paper, a novel three-phase three-level LC-type series resonant dc/dc converter was proposed. The converter has the advantage of fewer switches and simpler configuration. The voltage stress on all switches can be reduced to the half of the input voltage, and the voltage across output rectifiers is clamped to the output voltage, as a result, the proposed converter is suitable for high input/output applications. Meanwhile, the ripple frequency of output current can be increased significantly, resulting in a reduced filter requirement. Variable frequency control strategy is adopted in order to obtain zero-voltage-switching for all switches and zero-current-switching for all rectifier diodes in wide input voltage and load range. In this paper, the operation principle of the converter was analyzed, along with the circuit model and gain characteristics of the converter according to fundamental harmonic analysis. Experimental results from a 440~590V input and 400V/5A output are presented to verify the theoretical analysis and the performance of the converter.