Patent ID: 7397678

Claim:
A method of providing a drive signal for a switch which controls the current drawn by an inductive energy storage element in a power factor correction circuit, wherein the power factor correction circuit includes a rectifier arrangement coupled to the inductive energy storage element and defining an input voltage therebetween, the power factor correction circuit further including output terminals for provision of an output voltage, and wherein a control signal is provided in the power factor correction circuit, the control signal operable to control power consumption in the power factor correction circuit, for one drive cycle of the switch the method comprising: a) detecting a predetermined storage state of the inductive energy storage element; b) producing a switching-on level for the drive signal when the predetermined storage state of the storage element is detected, wherein the switching-on level for the drive signal is produced (i) for a regular switched-on duration which is dependent on the control signal or (ii) for a maximum switched-on duration which is dependent on an input voltage, when the regular switched-on duration is greater than the maximum switched-on duration; c) producing a switching-off level for the drive signal for a switched-off duration until a subsequent detection of the predetermined storage state of the inductive energy storage element; and d) determining the input voltage from the switched-on duration, the switched-off duration, and the output voltage or a signal dependent upon the output voltage.