A switching regulator control circuit for use in a switching regulator, the switching regulator including: 1.1 a first switch having a first terminal thereof connected to a first application terminal to which an input voltage is applied; 1.2 a second switch having a first terminal thereof connected to a second terminal of the first switch and having a second terminal thereof connected to a second application terminal to which a voltage lower than the input voltage is applied; and 1.3 an overcurrent sensor configured to monitor a potential difference between the first and second terminals of the second switch to sense an overcurrent through the second switch, 1.4 the switching regulator control circuit being configured to generate a switching signal for controlling ON/OFF operation of the first switch, wherein 1.6 the switching regulator control circuit comprises: 1.7 a fault detector configured to detect, based on a duty ratio of the switching signal or a variable correlated to the duty ratio and included in a control signal used to generate the switching signal, a fault state where the duty ratio falls outside a normal modulation range; and 1.8 a fault protector configured to stop the switching of the first switch to turn the first switch OFF when the fault detector detects the fault state, wherein 1.9 the switching regulator control circuit is configured to limit an upper limit of a pulse width of the switching signal to a fixed width, 1.10 the switching regulator control circuit is configured to inhibit any pulse from occurring in the switching signal during a period in which an overcurrent is sensed by the overcurrent sensor, and 1.11 the fault detector is configured to detect the fault state when a plurality of pulses with the fixed width are occurring successively in the switching signal at a switching frequency of normal operation during a continuous period in which no overcurrent is sensed by the overcurrent sensor. 1.1 a first switch having a first terminal thereof connected to a first application terminal to which an input voltage is applied; 1.2 a second switch having a first terminal thereof connected to a second terminal of the first switch and having a second terminal thereof connected to a second application terminal to which a voltage lower than the input voltage is applied; and 1.3 an overcurrent sensor configured to monitor a potential difference between the first and second terminals of the second switch to sense an overcurrent through the second switch, 1.4 the switching regulator control circuit being configured to generate a switching signal for controlling ON/OFF operation of the first switch, wherein 1.6 the switching regulator control circuit comprises: 1.7 a fault detector configured to detect, based on a duty ratio of the switching signal or a variable correlated to the duty ratio and included in a control signal used to generate the switching signal, a fault state where the duty ratio falls outside a normal modulation range; and 1.8 a fault protector configured to stop the switching of the first switch to turn the first switch OFF when the fault detector detects the fault state, wherein 1.9 the switching regulator control circuit is configured to limit an upper limit of a pulse width of the switching signal to a fixed width, 1.10 the switching regulator control circuit is configured to inhibit any pulse from occurring in the switching signal during a period in which an overcurrent is sensed by the overcurrent sensor, and 1.11 the fault detector is configured to detect the fault state when a plurality of pulses with the fixed width are occurring successively in the switching signal at a switching frequency of normal operation during a continuous period in which no overcurrent is sensed by the overcurrent sensor. 1.7 a fault detector configured to detect, based on a duty ratio of the switching signal or a variable correlated to the duty ratio and included in a control signal used to generate the switching signal, a fault state where the duty ratio falls outside a normal modulation range; and 1.8 a fault protector configured to stop the switching of the first switch to turn the first switch OFF when the fault detector detects the fault state, wherein 1.9 the switching regulator control circuit is configured to limit an upper limit of a pulse width of the switching signal to a fixed width, 1.10 the switching regulator control circuit is configured to inhibit any pulse from occurring in the switching signal during a period in which an overcurrent is sensed by the overcurrent sensor, and 1.11 the fault detector is configured to detect the fault state when a plurality of pulses with the fixed width are occurring successively in the switching signal at a switching frequency of normal operation during a continuous period in which no overcurrent is sensed by the overcurrent sensor.