POWER SUPPLY SYSTEM

A power supply system includes: a plurality of battery cells interconnected between a first stack node and a second stack node and providing a first operation voltage to a high-voltage board net; a low-voltage battery interconnected between the second stack node and a low voltage node and outputting a second operation voltage to a low-voltage board net; a step-down converter interconnected between the first stack node and the second stack node and outputting a third operation voltage to the low voltage node to charge the low-voltage battery; an intermediate node dividing the battery cells into first and second subsets of the battery cells and being connected to the low voltage node via a first switching element; and a control unit configured to detect a terminal voltage of the low-voltage battery and to set the first switching element into a conductive state according to the detected terminal voltage.