A new universal full-directional SiC-GaN-based two-phase DC-DC converter has been recently introduced. It is supposed to replace with DC-DC battery charger and DC-DC traction drive converters in Plug-In Electric Vehicles. The SiC-GaN-based converter is designed to have the advantage of low switching power loss of GaN in hard-switching application and also avoid a high number of paralleled phases for high power multi-phase DC-DC converter applications. Especially in this paper, a dead-time analysis is done for the state-of-the-art high power GaN and SiC components of the proposed converter. To this aim, a new Spice-based simulation method is presented to obtain precise dead-time power loss calculations. Furthermore, the effect of negative OFF gate-source voltage is investigated.