A DC-DC converter comprising: a first converter configured to convert an input voltage into a first power supply voltage; a duty ratio controller configured to generate a duty ratio control signal (DTCS) for controlling a duty ratio of a switching pulse of the first converter; a switching frequency controller configured to generate a switching frequency control signal controlling a driving frequency of the first converter corresponding to a switching frequency of the switching pulse; and a current sensor configured to sense a current flowing through the first converter, wherein, the first converter is configured to be driven at the switching frequency of a first frequency in a first mode, based on the switching frequency control signal, and generates the first power supply voltage of a first level, based on the duty ratio control signal (DTCS), the first converter is configured to be driven at the switching frequency of a second frequency different from the first frequency in a second mode, based on the switching frequency control signal, and generates the first power supply voltage of a second level different from the first level, based on the duty ratio control signal (DTCS), and the switching frequency controller is configured to determine whether to turn off the current sensor; characterized in that the switching frequency controller is configured to calculate a target duty ratio based on a voltage level of the input voltage and a target voltage level (T_VSS) corresponding to the second level, to calculate a correction switching frequency corresponding to the second frequency based on the target duty ratio, and to generate the switching frequency control signal based on the correction switching frequency, and the switching frequency controller comprises: a current sensor controller which is configured to turn off the current sensor when the correction switching frequency is lower than a reference frequency in a power saving mode corresponding to the second mode, in order to reduce a minimum on-time even when the DC-DC converter is driven at the reference frequency higher than the calculated second frequency, wherein the reference frequency refers to the lowest switching frequency of the first converter at which output ripples do not occur, and may be a value preset by experimentation. a first converter configured to convert an input voltage into a first power supply voltage; a duty ratio controller configured to generate a duty ratio control signal (DTCS) for controlling a duty ratio of a switching pulse of the first converter; a switching frequency controller configured to generate a switching frequency control signal controlling a driving frequency of the first converter corresponding to a switching frequency of the switching pulse; and a current sensor configured to sense a current flowing through the first converter, wherein, the first converter is configured to be driven at the switching frequency of a first frequency in a first mode, based on the switching frequency control signal, and generates the first power supply voltage of a first level, based on the duty ratio control signal (DTCS), the first converter is configured to be driven at the switching frequency of a second frequency different from the first frequency in a second mode, based on the switching frequency control signal, and generates the first power supply voltage of a second level different from the first level, based on the duty ratio control signal (DTCS), and the switching frequency controller is configured to determine whether to turn off the current sensor; characterized in that the switching frequency controller is configured to calculate a target duty ratio based on a voltage level of the input voltage and a target voltage level (T_VSS) corresponding to the second level, to calculate a correction switching frequency corresponding to the second frequency based on the target duty ratio, and to generate the switching frequency control signal based on the correction switching frequency, and the switching frequency controller comprises: a current sensor controller which is configured to turn off the current sensor when the correction switching frequency is lower than a reference frequency in a power saving mode corresponding to the second mode, in order to reduce a minimum on-time even when the DC-DC converter is driven at the reference frequency higher than the calculated second frequency, wherein the reference frequency refers to the lowest switching frequency of the first converter at which output ripples do not occur, and may be a value preset by experimentation.