Systems and methods for driving light emitting diodes

摘要

System and methods are provided for driving one or more light emitting diodes (LEDs) to reduce audible noise. An example system includes a switching component, a system controller, and a current generator. The switching component is configured to receive a dimming signal with a predetermined dimming frequency and configured to switch on or off the one or more LEDs in response to the dimming signal, the predetermined dimming frequency being outside a frequency band of the audible noise. The system controller is configured to receive a feedback signal related to a LED current that flows through the one or more LEDs and configured to generate a drive signal. Additionally, the current generator is configured to receive the drive signal, to generate a charging current to store energy during a charging period and to generate the LED current during a discharging period.

主权项

1. A system comprising:
a dimming controller configured to generate (i) a first dimming signal having a first dimming frequency, and (ii) a second dimming signal having a second dimming frequency; a first LED switch configured to receive the first dimming signal, and to switch on or off a first LED string in response to the first dimming signal; a second LED switch configured to receive the second dimming signal, and to switch on or off a second LED string in response to the second dimming signal, wherein the second LED string is coupled in parallel with the first LED string; and a detection circuit configured to generate a comparison signal indicating whether a first voltage drop of the first LED string is larger than a second voltage drop of the second LED string, wherein the dimming controller is further configured control the first dimming signal and the second dimming signal to
(i) in response to the comparison signal indicating the first voltage drop is larger than the second voltage drop, keep the first LED string on when the second LED string is on, and(ii) in response to the comparison signal indicating the first voltage drop is smaller than the second voltage drop in magnitude, keep the second LED string on when the first LED string is on.