A new approach for high efficiency buck-boost DC/DC converters using series compensation

This paper proposes a new buck-boost DC/DC converters, which is connected in series to the power supply. The proposed circuit provides only differential voltage between the input voltage and the output voltage command. The power rating of a conventional circuit is dominated by the input voltage or the output voltage. In contrast, the voltage rating of the proposed circuit requires only the differential voltage between the input and output voltage. In addition, the series converter generates a positive and negative voltage to realize boost mode and buck mode, respectively. As a result, the power rating of the DC/DC converter can be drastically reduced. A new approach for series compensation converters is introduced in order to realize high efficiency and a reduction of power rating. Two new buck-boost converters and their control methods are proposed based on a new concept in which the proposed circuits consist of an Hbridge circuit and a power assist circuit. The H-bridge circuit is used in order to determine the polarity of the differential voltage. The power assist circuit controls the DC voltage of the H-bridge circuit depending on the output voltage command. In the proposed circuit, a flyback converter and inverting chopper are used as the power assist circuit. Simulation and experimental results are shown in order to demonstrate the advantages of the proposed converters in comparison with a conventional buck-boost converter. A maximum efficiency of 98% was obtained with the proposed circuit. The proposed circuits can decrease losses by 2/3 in comparison with a conventional buck-boost converter. Therefore, the proposed converter can realize high efficiency and down-sizing in applications that require the output voltage to be closed to the input voltage.