A Customised Low-voltage Power Supply for a Formula SAE Electric Racing Vehicle

This paper presents a custom-built low-voltage (LV) power supply for a Formula SAE (FSAE) electric racing car that eliminates the dependence on the vehicle's LV battery to operate the car's essential functions while the high-voltage (HV) bus is enabled. The power supply consists of a 240 W LLC resonant converter followed by a low-loss priority switch that manages the automatic changeover between a lower-capacity LV battery and the vehicle's HV accumulator battery. The solution incorporates customised circuitry to implement various power converter functions, e.g., start-up supply, under-lover-voltage lockout, over-current protection, and system monitoring/reporting to the vehicle control unit. The overall system (including the priority switch stage) operates at an efficiency of 95 %, and complies with all requirements set by the FSAE rules. Selected experimental results are provided to demonstrate the LV supply operation under dynamic conditions.