The present invention refers to a switching power supply, in particular to a power factor corrector, and more particularly to a circuit for the programmable protection against output over-voltages. It also refers to a power factor corrector integrated circuit comprising a circuit for the programmable protection against output over-voltages. In one embodiment the circuit for the programmable protection against output over-voltages in a power Factor corrector comprises means for detecting a signal proportional to the output voltage; a first preset reference voltage; a second preset reference voltage; a transconductance amplifier which receives in input the signal proportional to the output voltage and the first preset reference voltage; a comparator which receives in input the signal proportional to the output voltage and the second preset reference voltage; means suitable for absorbing a current coming from the signal proportional to the output voltage.