Abstract: To realize the full power band ZVS of the dual active bridge direct current direct current(DC-DC) converter when the input and output voltages are mismatched, an extended-phase-shift optimization control method based on inductor current constraints is proposed. First, the internal phase shift angle of the converter is redefined for the buck and boost modes, which is defined as the phase shift difference between the primary-side full-bridge switching tubes when the converter operates in the buck mode, and that between the secondary-side full-bridge switching tubes when the converter operates in the boost mode and analyzed for the operating characteristics in the different operating modes. Then, according to the realization conditions of zero voltage switching(ZVS), the constraints of inductor current are introduced, so as to derive the calculation formula of phase shift angle and the range of transmitted power in different operation modes, and further compared with different control schemes, which theoretically proves the superiority of the proposed optimized control strategy. Finally, an experimental platform is built to verify the effectiveness of the proposed optimized control strategy. The experimental results show that the optimized extended-phase-shift control can realize the full power band ZVS in buck and boost mode, which significantly improves the efficiency of the converter in the low-power band.