Design and evaluation of a solar based single inductor multiple outputs LED lighting

When driving the paralleled LED strings, the large forward tolerance across the LED will result in the current nonuniformly distributed between each string, which causes LEDs to be overdriven and influence the lifespan. This paper presents a single inductor multiple outputs parallel string LED driver with time multiplexing control schemes. Two kinds of pulse-width modulation schemes are presented and compared. The system architecture, operation principle, simulation and hardware implementation results are demonstrated. The efficiency of the LED driver based on PWM scheme II approaches 88.9% with less than 5% current mismatch between each parallel LED strings, an improvement over PWM scheme I.