LED Driver with Self-Optimized Channel Voltage - A Switch-Mode Voltage Regulator Optimizes an Active Current Regulator for a LED Driver

摘要

A novel LED driver with multiple LED-channels is presented, consisting of an active current regulator and a switch-mode voltage regulator for each channel. The active current regulator means no current-sensing resistor and directly controls an LED-current. The switch-mode voltage regulator optimizes the channel voltage by means of keeping a minimum voltage drop across the active current regulator to barely supply a desired current to the LEDs. This self-optimization can be independently achieved for each channel. The proposed driver is designed by 0.35μm 40V high voltage process. Simulation results show that when the voltage drop across the LEDs is different for each channel, the proposed LED driver can adapt the channel voltage to a threshold voltage for normal operation and regulate an LED-current to obtain desired luminous intensity. Roughly, the proposed driver has a power-conversion efficiency of above 85%.