Power system includes a power connector, a voltage detecting unit, a cell array, and a micro-controller unit. The power connector is used for providing at least one output voltage. The voltage detecting unit is coupled to the power connector for detecting voltage levels of at least one output voltage. The cell array is coupled to the power connector for providing energy of at least one output voltage. The cell array includes M cell packs coupled in parallel. Each cell pack includes six transistors and a power storage unit. The micro-controller unit is coupled to the voltage detecting unit and the cell array for controlling each transistor in all cell packs.