WIRELESS CHARGING CIRCUIT, WIRELESS CHARGING SYSTEM AND SEMICONDUCTOR DEVICE

To satisfy the NFC communication standard in wireless charging with a shared antenna, used for NFC communication. A power supply unit includes a voltage step-down circuit 331, a charge control circuit 332, and a communication controller power supply circuit 333. The voltage step-down circuit includes a switching regulator 200, and a selection circuit 206 and 208 which can select an output path PT1 of the switching regulator and a bypass path PT2 of the switching regulator. The voltage step-down circuit includes a selection control circuit 207. The selection control circuit supplies voltage to the communication controller power supply circuit via the bypass path at the time of activating the communication controller. Since the output voltage of the series regulator stabilizes in a shorter time than the switching regulator, it becomes possible to keep the time from when RF power rises to when initial communication becomes possible, within standards.