The voltage of a detection resistor connected to the drain of a low-side switching device is normally a negative voltage, but a positive voltage appears when a countercurrent occurs in an abnormal state. A current comparator monitors the voltage of the detection resistor, transmits high output to an AND circuit whole the voltage of the detection resistor is a negative voltage to maintain the output voltage of the current comparator in a low state when an output signal of a driver can be transmitted to the low-side switching device, and allows the output voltage of the current comparator in a low state when the voltage of the detection resistor becomes a positive voltage, thereby forcibly turning off the low-side switching device.