Method for driving a switch that controls current drawn in a power factor correction circuit and a drive circuit therefor

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 includes 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) providing a current measurement signal which is dependent on an input current to the inductive energy storage element;
• c) 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) until a peak value which is dependent on an input voltage of the input current is reached, if the peak value is reached within the regular switched-on duration;
• and
• d) 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.

A drive circuit for production of a drive signal for a switch which controls the current drawn in a power factor correction circuit, the power factor correction circuit including a rectifier arrangement coupled to an inductive energy storage element with an input voltage defined between the rectifier arrangement and the inductive energy storage element, the drive circuit comprising:

• a) a first input configured to receive a control signal which is operable to regulate the power consumption, and a second input configured to receive a magnetization signal which indicates a storage state of the inductive energy storage element;
• b) an output configured to provide the drive signal;
• c) a logic storage element operable to switch to a first storage state as a function of the magnetization signal in order to produce a switching-on level for the drive signal, the logic storage element further operable to switch to a second storage state as a function of a switching-off signal in order to produce a switching-off level for the drive signal;
• d) a signal production circuit operable to produce the switching-off signal as a function of the control signal and the input voltage, wherein the signal production circuit is designed to produce the switching-off signal at the latest after a maximum switched-on duration or upon reaching a maximum input current, with the signal production circuit determining the maximum switched-on duration or the maximum input current from the input voltage or from a signal derived from it.