Dual-port USB is developed with the increase of electronic portable devices in recent years, and the birth of some devices with large charging current. Previous mobile phones, MP3 and other portable devices have smaller battery capacity, smaller requirements for chargers, and generally charging current within 0.5A. In recent years, smart phones and tablets have developed rapidly, and these devices are generally equipped with large-capacity batteries due to their high power consumption, in order to provide sufficient battery life, so the requirements for chargers have gradually increased.