Patent ID: 8193793

Claim:
A DC-DC converter comprising: an inductor to convert a voltage; a drive switching element to apply a direct-current input voltage supplied from a direct-current power source to the inductor, so that a current flows and so as to accumulate energy in the inductor; a rectification element to rectify the current in the inductor during an energy discharging period in which the drive switching element is turned off; and a switching control circuit comprising: an error amplifier to output a voltage according to an output voltage, and a PWM comparator to compare an output of the error amplifier with a waveform signal having a predetermined frequency, and a PFM comparator to compare the output of the error amplifier with a predetermined reference voltage, so that the switching control circuit generates a signal to control turning on and off of the drive switching element, based on an output of the PWM comparator and an output of the PFM comparator, wherein a PWM control is performed based on the output of the PWM comparator when a load is larger than a predetermined value and a PFM control is performed based on the output of the PFM comparator when the load is smaller than the predetermined value, wherein the switching control circuit comprises a clamp circuit to clamp the output of the error amplifier so as not to be lower than a predetermined voltage when the PFM control is performed, and wherein by clamping the output of the error amplifier by the clamp circuit when the PFM control is performed, a PWM pulse output in the PWM control from the PWM comparator, which compares the output of the error amplifier with the waveform signal, is regulated so as not to be smaller than a predetermined pulse width.