LED DRIVING APPARATUS CAPABLE OF ADJUSTING SWITCHING DUTY RATIO FOR MULTI-CHANNEL LED APPLICATION

摘要

A light emitting diode (LED) driving apparatus capable of adjusting a switching duty ratio according to the present invention can comprise: a first delay loop which receives a pulse train of a reference pulse width modulation (PWM) signal, generates a rough delay signal which is formed by roughly delaying the reference PWM signal by one period of a pulse, and activates a rough delay fixing signal when a phase difference between the rough delay signal and the reference PWM signal decreases to be smaller than or equal to a predetermined value; a second delay loop which generates a second delay signal by finely delaying a phase of the rough delay signal, when the rough delay fixing signal is activated; a duplication delay line which delays a phase of the reference PWM signal while maintaining phase delay characteristics of the first delay loop and the second delay loop and outputs a duplication delay signal; and a comparator which receives a voltage difference signal between a detection voltage by a driving current for one of a plurality of LED strings having different equivalent resistances and a predetermined reference voltage, and the duplication delay signal, and outputs a switching signal. The switching signal can have a duty rate for equalizing magnitudes of average currents for each of the LED strings according to a magnitude of a voltage difference signal between a detection voltage by the driving current of the one of the LED strings with different equivalent resistances and a predetermined reference voltage.