A Control Method of Dual Active Bridge DC-DC Converters Maintaining Soft-Switching at Different Voltage Ratio

In recent years, a system using renewable energy has attracted attention, and power converters with high power efficiency and low cost are required. Dual Active Bridge (DAB) DC- DC converters are attracting attention because of their high power-efficiency due to Zero Voltage Switching (ZVS) operation over a wide load range. However, when the voltage input/output ratio is different from the turns ratio of the transformer, there is a disadvantage that the ZVS operation cannot be achieved at light loads, and the power efficiency drops. Therefore, this paper proposes a digital control method that can improve power efficiency at light loads regardless of the voltage input/output conversion ratio. In the experiment, it was confirmed that the power efficiency at light loads could be improved by about 10% when the input/output ratio is 200V / 150V, 150V / 100V, and 125V / 75 V.