An additional function device of an external power supply module includes a converter and a connecting line. With an input port configured at the converter in the additional function device, detachable assembly and connection to a power core unit can be achieved, and a plurality of power core units can be further assembled and connected to achieve a composite or redundant power output. Thus, the additional function device of an external power supply module is provided with diversified matching capabilities, enabling the additional function device of the external power supply module to be effectively utilized and reducing resource waste.