Patent ID: 7843186

Claim:
A step-down switching regulator comprising: a first switch configured to switch in accordance with a first control signal; an inductor configured to store charge from an input voltage based on the first switch; a second switch configured to discharge the charge stored in the inductor in accordance with a second control signal; a controller configured to generate a proportional voltage based on an output voltage and to control the first and second switches so as to make the proportional voltage similar to a predetermined main reference voltage; a PWM control circuit and a PFM control circuit, each being connected to the controller so that both the PWM and PFM control circuits can direct the controller to drive both the first and second switches; and a detector configured to detect a change of the proportional voltage and output detection results to the controller when the proportional voltage exceeds a first predetermined reference voltage, or falls below a second predetermined reference voltage that is lower than the first predetermined reference voltage, wherein activation and deactivation of the first and second switches is based solely on outputs of the detector, such that the controller shuts the first switch off when the proportional voltage exceeds the first predetermined reference voltage and shuts the second switch off when the proportional voltage falls below the second predetermined reference voltage, and wherein the detector further includes: a first comparator configured to output a predetermined first signal to the controller when the proportional voltage exceeds the first predetermined reference voltage and activation and deactivation of the first switch is based solely on the output of the first comparator; a second comparator configured to output a predetermined second signal to the controller when the proportional voltage falls below the second predetermined reference voltage and activation and deactivation of the second switch is based solely on the output of the second comparator; resistors connected between an input terminals of the first comparators and an input terminal of the second comparator; and a high-pass filter formed of a capacitor and the resistors and wired to a connecting node of the resistors to input a signal based on the proportional voltage, and wherein: the connecting node of the resistors is wired to input terminal of the first and second comparator; a first voltage is input to an input terminal of the first comparator and a second voltage which is lower than the first voltage is input to an input terminal of the second comparator; and an intermediate voltage between the first and second voltages is input to other input terminals of the first and second comparators by adding the proportional voltage through the high-pass filter.