Efficiency Analysis of Four-Switch Buck-Boost Converter in Two-mode Modulation and Quadrangle Modulation

Abstract

The Four-Switch Buck-Boost (FSBB) converter is a non-isolated, bidirectional DC/DC converter with a wide input/output voltage range, making it particularly suitable for battery-connected applications. The modulation methods of the FSBB converter include two-mode modulation and quadrangle modulation. In two-mode modulation, the switching operation of one leg is conducted while the switching operation of the other leg is fixed according to the buck or boost operation mode. On the other hand, quadrangle modulation operates all switches to shape the inductor current into a rectangular waveform. Two-mode modulation is simple to implement; however, it has drawbacks due to high switching losses caused by hard switching operation. In contrast, quadrature modulation allows all switches to achieve zero-voltage switching (ZVS) turn-on operation. However, it has the drawbacks of high peak current and the requirement that all switches must perform switching. Therefore, even though quadrangle modulation performs ZVS turn-on operation, its efficiency may be lower than that of two-mode modulation, which operates with hard switching. This paper analyzes the losses of two-mode modulation and quadrant modulation based on the input-to-output voltage ratio, load conditions, and inductance used in the converter.