The document describes a method and an actuating circuit for actuating a switch regulating the power consumption in a power factor correction circuit which has input terminals for applying an input voltage and output terminals for providing an output voltage. In this case, the switch is cyclically turned on for an on-time and turned off for an off-time, respectively, with the on-time having a first on-time period and a second on-time period which is directly adjacent to the first on-time period. A length for the first on-time period is in this case dependent on the control signal, and a length for the second on-time period is proportional, at least for a prescribed range of values for an instantaneous value of the input voltage, to a quotient with a first first-degree function for this instantaneous value in the denominator and a second first-degree function for the instantaneous value in the numerator, with function values for the first function increasing as the instantaneous value rises.