Patent ID: 7791399

Claim:
An over-voltage protection circuit, comprising: an input terminal to receive an input voltage; a voltage-dividing circuit comprising a first resistor and a second resistor connected in series between the input terminal and ground; a voltage-stabilizing circuit comprising a voltage-stabilizing element; a control circuit comprising a transistor, a third resistor, a fourth resistor, and a fifth resistor, the transistor comprising a gate connected to the voltage-stabilizing circuit via the third resistor, a drain connected to the input terminal via the fourth resistor, and a source grounded, and the fifth resistor connected between the drain and the source of the transistor; a switching element; and an output terminal; wherein the voltage-dividing circuit is operable to provide a reference voltage according to the input voltage to the voltage-stabilizing circuit, the voltage-stabilizing circuit is operable to determine whether the voltage-stabilizing element conducts according to the reference voltage, and the control circuit is operable to control the switching element to switch on or off according to a conductive state of the voltage-stabilizing element to determine whether the output terminal outputs an output voltage, when the voltage-stabilizing element conducts, the switching element switches off causing the output terminal not to output the output voltage, when the voltage-stabilizing element is cut off, the switching element switches on causing the output terminal to output the output voltage via the switching element.