Three-level buck-boost dc-dc converter with voltage-lift-type switched-inductor

The three-level (TL) dc-dc converter have advantages of low voltage stress of the switches and diodes, and reduction of filter size. However, in order to achieve high step-up voltage gain, very high duty ratio of switches is required because their output voltage gain is the same as the traditional dc-dc converters. This paper proposes a new type of TL buck-boost dc-dc converter. The proposed converter is a transformerless dc-dc converter with a double self-lift switched-inductor cell inserted to the nonisolated TL buck-boost converter, which increases the voltage gain in the boost operation without very high duty ratio of switches. The proposed converter achieves high step-up and down voltage gain with maintaining advantages of the TL buck-boost converter. The operational principles and steady-state analysis have been verified by PSIM simulation and circuit experiments.