An Interchangeable Soft-Switched Voltage Boosting Circuit for a Multi-Mode LLC Step-Up Converter Module in Medium Voltage Applications

A new dc-dc LLC resonant converter with four configurable modes of operation is proposed in this paper. The proposed converter employs a reconfigurable full-bridge to asymmetrical half-bridge at the input-side and reconfigurable voltage doubler to voltage quadrupler rectifier at the output side, using only one low profile switch. The input voltage range is widely extended within a limited frequency range by changing the configurations and using a hybrid control technique. Reduced circulating current, and conduction losses of the LLC resonant tank as well as zero voltage switching for all silicon carbide (SiC) switches and zero current switching for all the diodes results in a high efficiency for a wide range of voltage gain and loading conditions in the proposed converter. The operation principles are analyzed and a proof of concept prototype with 300-700V input voltage and 6.6kV output voltage is built and tested to evaluate the feasibility of the proposed method.