Hello Khaledsailan,

In the simplest control scheme (single phase shift), the diagonal switch pairs in the primary and secondary of a dual active bridge (DAB) operate at a 50% duty cycle. Under the right operating conditions with proper design, when diagonal switch pairs turn off, the current through the leakage inductor starts to flow through the body diode of the complementary switch positions during the converter deadtime. This means that these devices are not blocking voltage when they turn on, thus achieving zero voltage switching (ZVS). The nuance of a DAB is designing the converter to achieve ZVS in the most operating conditions possible. Our partner, Texas Instruments, has a more detailed guide with diagrams found here showing how the circuit achieves ZVS, and Wolfspeed has more information in the whitepaper found here and in the CRD60DD12N-GMB design files.

For a software implementation, many controllers with a power-electronics focus such as the Texas Instruments C2000 line of controllers include features to introduce a phase shift between one or more of the pulse width modulation (PWM) outputs. The C2000 version of this feature is called EPWM_setPhaseShift. I recommend using these integrated features for the software.

Thanks,
Chris N.