LED driver with self-optimized channel voltage: A switch-mode voltage regulator optimizes an active current regulator for a LED driver

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 0.35 ¿m 40 V 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%.