Over voltage protection cirtcuit

PURPOSE: An overvoltage preventing circuit is provided to efficiently prevent an overvoltage from being inputted to a main circuit by turning off an input switch when the overvoltage occurs due to an external input voltage. CONSTITUTION: An input receiving terminal(NRI) receives an input voltage(VIN). An input switch(SWI) is formed between the input receiving terminal and an input transmitting terminal. A control signal generating block(BKGC) generates a switch control signal(XSC) by sensing a transmission voltage(VRC). The control signal generating block includes a feedback signal generating unit(110) and a control signal generating unit(130). The feedback signal generating unit generates a feedback signal(XFB) by sensing the transmission voltage. [Reference numerals] (133) Delay unit; (AA) Main circuit