<p>In ultra-precision motion control systems, nonlinear distortion of the output current in the power converter can induce unintended torque ripples in motors, which compromises control accuracy. To mitigate this issue, a deadband-free dual-buck symmetrical half-bridge power converter (DBSHPC) is employed to enhance output current linearity. However, under high-frequency operation, distributed capacitance and driving delay introduce additional dynamic distortions that are often overlooked, especially in dual-buck topologies. For this reason, this paper develops a switching transient model for the DBSHPC, incorporating the effects of distributed capacitance and driving delay on the GaN high electron mobility transistors (GaN HEMTs) drain-source voltage and current. Modal timing diagrams and mathematical expressions are derived for the turn-on/turn-off processes. Furthermore, the effects of driving parameters and parasitic parameters on GaN HEMTs drain-source voltage and current are analyzed. Within a certain range, when the distributed capacitance increases, the current overshoot and voltage overshoot increase approximately linearly. Finally, the feasibility of the theory is verified by experiments.</p>