A power supply apparatus for an X-ray imaging system. A capacitor unit including a plurality of capacitor cells is connected in series to a single cell battery, such that the capacitor unit is charged using the single cell battery. Only when respective capacitor cells of the capacitor unit are charged, respective balance circuits corresponding to the respective capacitor cells are controlled to be turned on. When the balancing of the respective capacitor cells is completed, the balance circuits are opened. Accordingly, the power consumption of the capacitor cells is minimized.
