Multimodal Split-Bus Boost-LLC Resonant Converter

This paper proposes a multimodal split-bus Boost-LLC resonant converter suitable for wide-range applications. In the proposed topology, the bus of the conventional full-bridge LLC resonant converter is split. Specifically, the bus of the first half-bridge arm is directly connected to the input voltage source, while the bus of the second half-bridge arm is boosted by an integrated Boost circuit formed by the Boost inductor connected to the input voltage source and the second bridge arm. A fixed-frequency duty cycle control is applied to the second switching bridge arm to raise its bus voltage, thereby adjusting the equivalent input voltage of the resonant tank and modifying the voltage gain of the converter. Additionally, through topological reconfiguration, the primary-side inverter bridge can transition from full-bridge mode to half-bridge mode, enabling the converter to achieve a fourfold voltage gain range. Finally, a 1 kW laboratory prototype with 400 V input and 200 V∼800 V output voltage was developed. Experimental results show that the prototype achieved 97.5% peak efficiency under full-bridge LLC mode, which increased to 97.8% when operating in half-bridge LLC mode. The efficiency remained above 96.2% within the whole output voltage range under the rated output current.