Disclosed herein is a low voltage direct-current (DC)-DC converter. The low voltage DC-DC converter includes a switching portion which includes a first switching portion and a second switching portion and changes a high voltage provided from a high voltage battery to an alternating current (AC) voltage, a transformer which converts the AC voltage output from the switching portion into a low voltage, and a switching portion zero voltage switching auxiliary circuit portion which is connected between the high voltage battery and the switching portion and operates when operations of the first and second switching portions change to consume residual energy in the switching portion.