According to one embodiment, a DC-DC converter includes a signal generator configured to output a first PWM signal having arbitrary amplitude and a duty cycle established based on an input voltage and an output voltage, a driver configured to output a second PWM signal being in phase with the first PWM signal and having amplitude of the input voltage based on the first PWM signal, a filter configured to extract a DC component from the second PWM signal, and a switch configured to supply an output of the filter to the signal generator in response to a first control signal.