Patent ID: 8531167

Claim:
A circuit adapted to a DC-DC converter supplying a target voltage to an external load connected to an output terminal, the DC-DC converter having a first switch element connected at a first end thereof to a power supply; a second switch element connected between a second end of the first switch element and ground; an inductor connected at a first end thereof to a node between the first switch element and the second switch element and connected at a second end thereof to an output terminal; and a capacitor connected between the output terminal and the ground, the circuit comprising: an error amplifier that amplifies a potential difference between a first voltage based on an output voltage at the output terminal and a reference voltage, and outputs a resultant error amplified signal; a differential detecting circuit that senses an inclination of a temporal change of the output voltage by differentiating the first voltage, outputs a control signal according to a result of the sensing, outputs a first boost signal as the control signal if the inclination exceeds a predetermined positive first threshold, outputs a second boost signal as the control signal if the inclination is less than a predetermined negative second threshold, and outputs a reference signal as the control signal if the inclination is between the predetermined positive first threshold and the predetermined negative second threshold; and a PWM generating circuit that compares a synthetic signal obtained by conducting computation on the amplified error signal and the control signal with a periodically changing comparison signal, and outputs a PWM signal having a duty ratio controlled according to a result of the comparison, wherein the first switch element and the second switch element are changed over in an on/off state in a complementary manner according to the PWM signal, if the first boost signal is contained in the synthetic signal, the PWM generating circuit controls the duty ratio in order to increase a ratio of the on-state of the second switch element, and if the second boost signal is contained in the synthetic signal, the PWM generating circuit controls the duty ratio in order to increase a ratio of the on-state of the first switch element.