Patent ID: 8614872

Claim:
A switching power source apparatus comprising: a high-side switch connected between an input voltage line and an inductor; a ramp signal generator configured to generate a ramp signal in synchronization with a switching frequency of the high-side switch; a superposing circuit configured to generate a second ramp signal having a positive inclination corresponding to the amplitude and frequency of the ramp signal and provide a superposed signal by superposing the second ramp signal on a first reference voltage; a controller configured to compare the superposed signal with a feedback signal corresponding to an output voltage, and if the feedback signal is lower than the superposed signal, control the ON timing of the high-side switch so that the high-side switch turns on; an overcurrent detector configured to detect if a current passing through an output load is an overcurrent; an OFF timer configured to determine a period during which the high-side switch is forcibly turned off based on a detection result of the overcurrent detector, the input voltage, and the output voltage, and generate a forcible OFF signal based on the determined period, wherein if the overcurrent detector detects an overcurrent, the controller turns off the high-side switch, and forcibly turns off the high-side switch for the determined period according to the forcible OFF signal, and a feedforward part configured to generate a feedforward current that is inversely proportional to the input voltage and proportional to the output voltage, wherein the OFF timer determines the period during which the high-side switch is forcibly turned off according to the feedforward current and a detection result of the overcurrent detector and generates the forcible OFF signal based on the determined period.