By analyzing the conditions of soft switch under single phase shift control of double active bridge, it is concluded that the soft switch cannot be implemented under light load of double active bridge when the voltage does not match. Therefore, based on single phase-shift control a single PWM control is introduced, and theoretically analyzing soft switching under the light load conditions, the result shows that single PWM control can enlarge the realization of soft switching range, but there is still blind area in the vicinity of the zero output power. This paper proposes a double PWM control, and derives that the dual PWM control can achieve soft switching when the output of double active bridge is close to zero power. Finally, the experiment of light load is analyzed, and the results show that the range of soft switching is increased by PWM control compared with single phase shift control.