A USB control system includes a first voltage controller, a control switch, a second voltage controller, and a PHY unit. The first voltage controller outputs a first internal voltage from an external voltage and a reference voltage, and the control switch regulates supplying and suspending the external voltage. The second voltage controller outputs a second internal voltage from the reference voltage and the external voltage applied through the control switch, and the PHY unit receives a request from a host using the first or second internal voltage as a voltage source. The power for certain internal blocks is suspended to reduce power consumption in the USB control system during a power-saving mode.