A DC-DC converter includes a PWM modulator, a power switch and a filter. The PWM modulator positively feeds back a pulse width modulated signal of which a pulse width and a frequency are varied to generate an oscillated signal, amplifies a difference between a negatively fed-back direct current output signal and a reference signal to output a first signal, and compares the first signal with the oscillated signal to generate first and second switching signals. The power switch transfers an input signal to a first output node in response to the first and second switching signals, and generates the pulse width modulated signal, wherein the pulse width modulated signal is provided to the first output node. The filter generates a direct current output voltage signal in response to the pulse width modulated signal, wherein the direct current output voltage signal is provided to a second output node.