Embodiments according to the present invention can enhance an efficiency of an apparatus or method capable of converting power of a system. An apparatus for converting power includes a load state variation detector that detects a load characteristic state of the load unit; and an adjusting unit that adjusts a preset value of the circuit device of the load unit in accordance with the value detected by the load state variation detector. A method for controlling a power includes checking a load characteristic with respect to one or more than one element of system elements; and adjusting one or more than one circuit device value of a power block of the one or more than one element with respect to the load characteristic. In embodiments, it is possible to increase an efficiency of a DC/DC converter by varying a turn ratio of an inductor among the circuit devices of a converter and adjusting an inductance L.