Patent ID: 8680778

Claim:
A circuit for operating at least one LED, comprising: a driver circuit with a coil and with a switch which is connected in series with the coil and clocked at a high frequency, the switch being controlled by a control unit, wherein when the switch is closed the coil is magnetized and when the switch is open the coil is demagnetized in a form of a current through the LED, wherein in a demagnetizing-current path when the switch is open a current-registering means is provided which supplies a current-registering signal to the control unit, wherein the control unit is adapted to ascertain a temporally averaged value of the current through the LED on a basis of a value of the current-registering signal at an end of an on-time cycle and also on the basis of a value at an end of a demagnetizing phase, wherein for a purpose of dimming the LED the control unit superimposes a comparatively low-frequency modulation on a high-frequency timing of the switch.