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The application of SiC power devices in high frequency auxiliary DC converters can greatly improve the power density of the system. The main loss source of phase- shifted full bridge converters in high frequency operation is the switching loss of devices in APU. It is particularly important for power devices to realize soft-switching. This paper mainly analyses the influence of different dead time on zero voltage switching (ZVS) of phase-shifted full-bridge lagging leg, and obtains the expression of dead time by theoretical calculation. Aiming at the problem of voltage oscillation, the transient equivalent circuit of the device is given, the mathematical model of voltage oscillation is established, the PSIM simulation model is built and tested on a 30 kW phase shifted full-bridge platform. The simulation and experimental results are in good agreement with the theoretical analysis. The peak voltage oscillation is proportional to the voltage at the front end of the device and the efficiency of the soft-switching converter reaches 97.4%, 1.83% lower than that of hard-switch, which verifies the importance of soft switching.