A DC-DC converter includes a high-side circuit supplied with a power supply voltage and a first internal reference voltage generated by a first regulator. The high-side circuit provides a current to an inductor, which is used for generating an output voltage. The first and second regulators each generate respective internal reference voltages. The second internal reference voltage is provided to a signal processing module, which controls the high side circuit so that the output voltage of the DC-DC converter corresponds to regulated target voltage level. The first and second regulators include a differential circuit comparing voltages and generating a corresponding comparison signal, a transistor for generating the internal reference voltage according to a gate voltage applied to its gate, and a circuit to change the gate voltage to reduce a signal amplitude of the comparison signal.