Research on FSBB Converter Based on Sub-Peak Current Constant Frequency Control

The Four-Switch Buck-Boost (FSBB) converter has been widely used in airborne secondary power systems in recent years because of its excellent wide voltage regulation capability, its soft-switching characteristics and the fact that its polarity of input and output voltages are the same. However, when the FSBB converter adopts the quadrilateral modulation strategy to realize Zero-Voltage Switching (ZVS), its negative current, inductance parameters, and several time state variables all affect the efficiency of the converter. Aiming at the above problems, this paper proposes a fixed frequency control strategy for the sub-peak current, which reduces the number of sampling circuits and can calculate the control variables in real time by sampling only the input voltage and output voltage. Finally, a 500 W experimental prototype with a switching frequency of 200 kHz is built to verify the proposed control strategy. The experimental results show that the FSBB converter achieves a peak efficiency of 97.2% and operates stably under a wide input voltage range.