Driving a light-emitting diode

摘要

An input stage (10) of an apparatus (1) for driving a light-emitting diode (40-42) receives a signal from a power supply (30-32), and an output stage (20) supplies a current to the light-emitting diode (40-42). The peak value divided by the average value of the current forms a ratio. The driving efficiency is improved by providing the input stage (10) with an arrangement (11) for reducing this ratio by manipulation of the signal, without the necessity of using any smoothing capacitors/inductors. The manipulation may comprise an addition of a frequency component to the signal or an adaptation of an amplitude of a frequency component of the signal. This frequency component may be a third and/or fifth and/or seventh harmonic frequency component of a fundamental frequency component of the signal. The arrangement (11) may comprise a resonant tank which may need to be tuned to the frequency component of the signal.