An AC-powered, flicker-free, multi-channel LED driver with current-balancing SIMO buck topology for large area lighting applications

This paper presents an AC-powered LED driver circuit that can drive multiple strings of LEDs with uniform brightness. The circuit basically has a two-stage topology in which the first-stage boost converter performs the power-factor correction (PFC) and the second-stage buck converter distributes equal DC currents to multiple LED channels using only a single inductor. The uniform current level, hence uniform brightness, is maintained via an open-loop fashion without the efficiency-degrading current-regulation elements. The single-inductor multiple-output (SIMO) buck converter connects the current-delivering inductor to each channel for an equal period of time, according to a permutating sequence to avoid systematic imbalances. A prototype LED driver demonstrates the maximum current difference of 1.93% while delivering 4.6-W to three channels of high-brightness white LEDs.