An Overall Analysis of the Static Characteristics of the Single Active Bridge Converter

Abstract

The dual active bridge (DAB) converter has been extensively analyzed and used in recent years for applications where bidirectional power flow is required. The unidirectional version of the DAB, which replaces the active output bridge with a diode bridge, has been called the single active bridge (SAB). The static behavior of the SAB differs markedly from similar DC/DC converters and can provide interesting advantages in certain applications. This paper presents a thorough study of the static behavior of the single active bridge (SAB) converter in different conduction modes. This study focuses on the description of the conduction modes, marking the main differences compared to similar DC/DC converters. Moreover, the SAB can be designed to operate in conduction mode for a given power level with different performance. A design guide is proposed, and the performance of different designs are compared, quantifying current stresses in the semiconductors. Finally, the main contribution of this paper is the identification of the similarities and differences between the SAB and the buck, forward, and phase-shifted full-bridge converters. It should be noted that the position of the inductor, either before or after the output rectifier bridge, modifies the voltage withstood by the output diodes and depends on the conduction mode, the voltage conversion ratio of the converter, and consequently, its main operation and performance. Moreover, the operation of the SAB is similar to a current source in all conduction modes, and it is not usual in similar converters. This peculiar behavior can be useful in certain applications. The theoretical study, the different designs, and the predicted operation of the SAB in different conduction modes have been validated using simulation and experimental results.