HIGH PERFORMANCE ADAPTIVE SWITCHED LED DRIVER

摘要

An LED driver controls current through an LED string. The LED driver generates a boosted PWM signal to drive a PWM transistor in the LED current path such that the PWM transistor maintains a substantially constant VGS, thus minimizing turn-on impedance of the PWM transistor. A current mirror circuit controls peak LED current when the PWM transistor is on. A trimming circuit includes a set of programmable switches to couple or decouple trimming transistor from the LED current path, and allowing for fine calibration of the LED current. By maintaining a low resistance and compensating for current mismatch in the LED current path, the LED driver provides efficient power performance and robustness that is particularly beneficial in high current applications.

主权项

1. A light-emitting diode (LED) driver for driving an LED string, the LED driver comprising:
an LED controller configured to generate a PWM signal; a first transistor to turn on or off responsive to the PWM signal, the first transistor in series with the LED string, wherein an LED current passes through the first transistor and the LED string when the first transistor is turned on; a second transistor in series with the LED string and the first transistor, wherein a first portion of the LED current passes through the second transistor when the first transistor is turned on; a programmable trimming circuit in parallel with the second transistor, the programmable trimming circuit configured to pass a trimming circuit current controlled by one or more trimming control signals, wherein the trimming circuit current comprises a second portion of the LED current.