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Dual active converter (DAB) can achieve high efficiency when the voltage ratio (the ratio of the input voltage to the output voltage equivalent to the primary side) is one, but when the voltage ratio is not one, the light-load efficiency drops sharply. Based on the realization logic of DAB light-load, this article proposes a modulation method with asymmetric compression duty cycle, which only increases one degree of freedom and does not need additional components to significantly improve the light-load efficiency. First, this article introduces the existing problems and solutions of the traditional scheme and puts forward a new modulation strategy. Then, the operating modes and power characteristics are analyzed. Then, the influence of duty cycle compression on reflux power and current stress is analyzed. Finally, a prototype with an input voltage of 100–200V, an output voltage of 50 V, and a full load power of 300–600 W is built to verify the analysis. [ABSTRACT FROM AUTHOR]