Patent ID: 8009400

Claim:
An interface circuit for connecting with a universal serial bus (USB) data cable, comprising: a USB connector for connecting with the USB data cable; an over voltage protection (OVP) circuit connected to the USB connector, the OVP circuit including an input connector, an output connector, and a control connector; the input connector connected to the USB connector; and a time delay circuit connected to the USB connector and the OVP circuit to control the OVP circuit, the time delay circuit being an RC time delay circuit that includes a capacitor, a first resistor and a second resistor connected in series between the USB connector and the ground, the control connector being connected between the first resistor and the second resistor; wherein the OVP circuit is switched off in a predetermined delay time of the time delay circuit when the USB data cable is connected to the USB connector, and is then switched on after the delay time of the time delay circuit.