A power conversion device comprising: a converter; a capacitor unit comprising a plurality of at least three capacitors (220-1, 220-2,..., 220-N) for accumulating an input voltage which is input thereto, wherein the plurality of capacitors (220-1, 220-2,..., 220-N) are connected in series, each of the plurality of capacitors (220-1, 220-2,..., 220-N) being configured to supply a voltage of a different level to the converter; a switch unit connected to the capacitor unit and comprising a plurality of switches (240-1, 240-2,..., 240-N) for selectively connecting one capacitor among the plurality of capacitors to the converter, wherein the switch unit further comprises reverse diodes connected in series to the other switches except for a first switch and a N-th switch among the plurality of switches, respectively; a controller connected to the capacitor unit and the switch unit, wherein the controller is configured to - determine a capacitor having a largest accumulated voltage, among the plurality of capacitors, as the capacitor satisfying a specified condition, - set two switches among the plurality of switches, to be turned on, the two switches corresponding to the capacitor, - set the other switches except for the two switches among the plurality of switches, to be turned off, so that the capacitor and the converter are electrically connected and the voltage accumulated in the capacitor is supplied to the converter; wherein the power conversion device further comprises: a load electrically connected to the converter; and a feedback controller configured to provide a feedback signal to the converter, based on an input voltage of the load. a converter; a capacitor unit comprising a plurality of at least three capacitors (220-1, 220-2,..., 220-N) for accumulating an input voltage which is input thereto, wherein the plurality of capacitors (220-1, 220-2,..., 220-N) are connected in series, each of the plurality of capacitors (220-1, 220-2,..., 220-N) being configured to supply a voltage of a different level to the converter; a switch unit connected to the capacitor unit and comprising a plurality of switches (240-1, 240-2,..., 240-N) for selectively connecting one capacitor among the plurality of capacitors to the converter, wherein the switch unit further comprises reverse diodes connected in series to the other switches except for a first switch and a N-th switch among the plurality of switches, respectively; a controller connected to the capacitor unit and the switch unit, wherein the controller is configured to - determine a capacitor having a largest accumulated voltage, among the plurality of capacitors, as the capacitor satisfying a specified condition, - set two switches among the plurality of switches, to be turned on, the two switches corresponding to the capacitor, - set the other switches except for the two switches among the plurality of switches, to be turned off, so that the capacitor and the converter are electrically connected and the voltage accumulated in the capacitor is supplied to the converter; - determine a capacitor having a largest accumulated voltage, among the plurality of capacitors, as the capacitor satisfying a specified condition, - set two switches among the plurality of switches, to be turned on, the two switches corresponding to the capacitor, - set the other switches except for the two switches among the plurality of switches, to be turned off, so that the capacitor and the converter are electrically connected and the voltage accumulated in the capacitor is supplied to the converter; wherein the power conversion device further comprises: a load electrically connected to the converter; and a feedback controller configured to provide a feedback signal to the converter, based on an input voltage of the load. a load electrically connected to the converter; and a feedback controller configured to provide a feedback signal to the converter, based on an input voltage of the load.