Undervoltage detection circuit and switching power supply

The utility model discloses an undervoltage detection circuit which is applied to a switching power supply, the switching power supply comprises a control detection module, and the undervoltage detection circuit comprises a detection module and a voltage stabilization module. The input end of the detection module is connected with input voltage Vin, and the first output end of the detection module is connected with the first input end of the voltage stabilization module and used for stabilizing the maximum voltage value output by the under-voltage detection circuit. The output end of the voltage stabilizing module is grounded; the second output end of the detection module is connected with the second input end of the voltage stabilization module and then is connected to the control detection module so as to transmit a detected input voltage signal to the control detection module. The undervoltage detection circuit can realize undervoltage detection in an ultra-wide input voltage range, improves the anti-inter