The brightness generated by LEDs in an LED strip is adjusted by pulse-width modulation, wherein the LEDs connected in series are driven temporally offset to one another. If there is a shift in the on-time of at least one LED, a controller inserts at least one additional drive pulse to switch on the LEDs if the interval of the on-times of an LED in the time frame before the shift and in the drive frame after the shift is so large that the interval arising therefrom exceeds a first threshold. Alternatively, the controller reduces at least one drive pulse for switching on the LEDs to curtail the on-time of the LEDs if the interval of the on-times of an LED in the time frame before the shift and in the time frame after the shift is so small that the interval arising therefrom drops below a second threshold.