Patent ID: 7535284

Claim:
A switching control circuit of a voltage generating circuit generating an output voltage of a target level from an input voltage by turning on and off a transistor applied with the input voltage, the switching control circuit controlling the transistor as to on and off, comprising: an error amplifier circuit configured to output an error voltage obtained by amplifying an error between a voltage according to the output voltage and a first reference voltage according to the target level; a first comparison circuit configured to compare between the error voltage and a second reference voltage changing at a predetermined frequency to output a first control voltage for turning on and off the transistor; a second comparison circuit configured to compare between the error voltage and a third reference voltage to: output a first voltage when the error voltage is higher than the third reference voltage; and output a second voltage when the error voltage is lower than the third reference voltage; a charging and discharging circuit configured to charge a capacitor based on the first voltage and to discharge the capacitor based on the second voltage; a third comparison circuit configured to compare between a charged voltage of the capacitor and a fourth reference voltage according to a capacitance of the capacitor; and a control circuit configured to output a second control voltage for turning off the transistor irrespective of the first control voltage, when a comparison result of the third comparison circuit in the case where the charged voltage of the capacitor is higher than the fourth reference voltage continues for a predetermined period.