A new adaptive switching frequency modulation for optimizing low power cascaded buck-boost converter

This paper presents a new technique to optimize the efficiency of the Cascaded Buck-Boost (CBB) converters by using adaptive switching frequency selection algorithm. Such bidirectional DC-DC CBB topology is typically deployed in PV-Battery systems. A precise loss-model that accounts for component nonlinearities is developed in which an optimal switching frequency is chosen that corresponds to the lowest total loss in both the buck and the boost modes of operation. Based on the developed algorithm, and once the optimal switching frequency is selected, a digital control system is designed to frequently adjust the selected optimal frequencies to modulate the PWM duty cycle accordingly and to take in account any load and line regulations. A 100 W CBB converter prototype is built to verify the developed algorithm and its loss model and to validate the theoretical efficiency improvement of the proposed adaptive switching frequency modulation technique.