Abstract: The present invention relates to an uninterruptible power supply for the backup of DC power source.

Abstract: The present invention relates to an uninterruptible power supply, more specifically, to an uninterruptible power supply for the backup of AC-power supply which comprises an electric double layer capacitor as an energy storage device. The uninterruptible power supply according to the present invention comprises an AC power source, a AC/DC converter which converts an AC input from the AC power source into an DC power, an energy storage device which stores an extra electric energy and a DC/AC inverter which converts DC input from the energy storage device into AC power and supplies the AC power to an output load at a power interruption, wherein the energy storage device is an electric double layer capacitor and a ratio of charging voltage of the electric double layer capacitor to a minimum operating voltage of the DC/AC inverter is adjusted to 1.3 times or higher.