The auxiliary power module (APM) in the electrical vehicle converts the high voltage of battery pack to the low voltage to supply the electric power for the internal loads, including electric power steering, electric turbo, headed windshield and cooling pumps. The increasing demands on charging time and mileage have made the battery packs with even higher voltage (e.g. 800 V) a promising option. However, it brings a new challenge for the APM, and either the 1.2‐kV silicon carbide (SiC) device or the three‐level (TL) topology are used conventionally. This work proposes a cost‐effective hybrid SiC/Si‐based T‐type TL LLC$ LLC$ resonant converter for the vehicular APM application with a high step‐down ratio. The 1.2‐kV SiC and 650‐V Si devices are used as the main and auxiliary switches, respectively. It fully utilizes the voltage rating of device, and also improves the efficiency compared with conventional TL topology. To improve the gain range and electromagnetic interference performance, a variable frequency and adjustable phase‐shift modulation scheme is adopted. At the same time, the steady‐state time‐domain model is established to elaborate the operation principles, topology features, and boundary conditions for soft‐switching. Furthermore, the precise solutions for switching frequency and phase‐shift angle are figured out. Finally, the effectiveness of model is verified by the simulation as well as the experiment. A 1‐kW prototype for the application in the APM is demonstrated with the input voltage of 640–840 V and a constant output of 48 V/ 21 A.