A power delivery (PD) controller integrated circuit (IC) and a control method for a power switch are provided. A first terminal and a second terminal of the power switch are respectively coupled to a power pin of a universal serial bus (USB) connector and a power input terminal of a functional circuit. The PD controller IC generates a power switch control voltage to control the power switch. The PD controller IC may adjust a level of the power switch control voltage in stages during a power-on period of the functional circuit to gradually turn on the power switch.