Soft-Switching Fixed-Frequency Control Strategy for Three-Level Buck-Boost Converter

A soft-switching fixed-frequency control strategy based on the non-inverting three-level Buck-Boost converter is proposed in this paper. Soft-Switching for all switches in the whole domain can be achieved by the specific inductor current waveform trajectories. Limiting conditions are imposed on the three duty cycle control variables, and the mathematical calculation results of the maximum output power point are provided. The linear modulation method that each duty cycle increases proportionally when the load current increases is proposed. The simple fixed frequency control strategy can be used easily, and can achieve ultra-wide range voltage regulation with smooth transitions between different operating conditions. Simulation results demonstrate the feasibility of this control strategy, and experimental validation will be conducted in the future.