Patent ID: 8803445

Claim:
A circuit for driving light emitting diodes, the circuit comprising: a first semiconductor switch that is responsive to a driver signal and a freewheeling device coupled between a first supply terminal that provides a supply voltage and a second supply terminal that provides a reference potential; an LED and an inductor coupled in series between a common circuit node of the first semiconductor switch and the freewheeling device and either the first supply terminal or the second supply terminal; a current measurement circuit coupled to the LED and configured to provide a load current signal that represents a load current passing through the LED; a first feedback circuit that comprises an on-off controller configured to receive the load current signal and a reference signal, to compare the load current signal with the reference signal and to generate the driver signal dependent on the comparison; a modulator configured to provide, as reference signal, a modulated signal having a desired duty cycle and an amplitude; and a second feedback circuit configured to receive the load current signal, to determine an average load current signal and to adjust an amplitude of the modulated reference signal dependent on a difference between the average load current signal and a reference value.