Disclosed herein is a universal serial bus port controller on a source side. The universal serial bus port controller is compatible with universal serial bus Type-C. A source is equipped with the universal serial bus port controller including a power supply terminal, a power supply circuit, a switch connected between an output of the power supply circuit and the power supply terminal, a capacitor connected to the power supply terminal, and a discharge resistance and a discharge switch connected in series with each other between the power supply terminal and a ground line. The universal serial bus port controller includes an abnormality detector which detects an output voltage of the power supply terminal a plurality of times after the discharge switch is turned on and detects an abnormality on the basis of a temporal change in the output voltage.