Dc-dc converter

A DC-DC converter supplying a target voltage to an external load connected to an output terminal, the DC-DC converter comprising:

• 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;
• a capacitor connected between the output terminal and the ground;
• a voltage divider circuit that outputs a first voltage obtained by conducting voltage division on the output voltage;
• an error amplifier that amplifies a potential difference between the first voltage 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 in other cases;
• 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.

A DC-DC converter supplying a target voltage to an external load connected to an output terminal, the DC-DC converter comprising:

• 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;
• a capacitor connected between the output terminal and the ground;
• an analog-to-digital converter that outputs a first signal obtained by conducting analog-to-digital conversion on the first voltage based on the output voltage at the output terminal;
• a differential detecting circuit that senses an inclination of a temporal change of the output voltage by differentiating the first voltage based on the first signal, 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 in other cases;
• and
• a duty computer circuit that compares a synthetic signal obtained by conducting computation on an amplified error signal which is a digital signal obtained by amplifying a potential difference between the first voltage and a reference voltage 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 duty computer 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 duty computer circuit controls the duty ratio in order to increase a ratio of the on-state of the first switch element.