Method and system for extending PWM dimming range in LED drivers

摘要

An apparatus for driving a light emitting diode (LED). A rising edge of a pulse width modulation (PWM) signal is first sensed. Upon sensing the rising edge, a threshold pulse (TP) signal is initiated that has a configured width started when the rising edge is sensed, an LED current with an amplitude at a previously set level is generated, and starting to charge a capacitor which yields a voltage Vcap. Subsequently, a falling edge of either the PWM signal or the TP signal is detected. Upon detecting the failing edge, the circuit stops charging the capacitor, samples, after a first delay from the detected falling edge, the voltage Vcap, and adjusts a level of the amplitude of the LED current based on the sampled voltage Vcap. When the falling edges of both the PWM and TP signal are detected, the LED current is terminated.