Output voltage overvoltage protection circuit and system used for switching power supply

The invention discloses an output voltage overvoltage protection circuit and system used for a switching power supply. The output voltage overvoltage protection circuit comprises a voltage current conversion module, an output voltage calculation module, and a voltage comparison module, wherein the input end of the voltage current conversion module is coupled to the positive electrode of the power supply of the circuit through a voltage-division resistor; the first input end of the output voltage calculation module is coupled to the output end of the voltage current conversion module while the second input end of the output voltage calculation module is used for receiving a feedback signal of a load circuit; the first input end of the voltage comparison module is used for receiving the output voltage transmitted by the output voltage calculation module while the second input end of the voltage comparison module is used for being coupled with the reference voltage; and the output end of the voltage comparison m