As the low-voltage power load of new energy vehicles continues to increase, the system topology becomes more and more complex. Therefore, the role of the vehicle's low-voltage power supply system becomes increasingly prominent. It is crucial to design an on-board low-voltage power supply system that meets functional safety requirements to ensure the safe operation of autonomous driving. However, current low-voltage power systems can only meet the functional safety requirements of ASIL B in ISO 26262. In addition, most current low-voltage power solutions still use 12V lead-acid batteries as backup energy storage devices. Such batteries contain lead and are not environmentally friendly. This article studies the functional safety-oriented supercapacitor low-voltage power supply system for new energy vehicles. First, from the perspective of functional safety, a topology structure using a combination of DC/DC converter and supercapacitor is designed. This lower cost, higher functional safety topology is then fully discussed and its different fault conditions and operating modes are explained in detail. The feasibility of this solution has been verified through system simulation and experiments.