Single-Switch Multichannel Current-Balancing LED Drive Circuits Based on Optimized SC Techniques

By combining the conventional switched-mode power converters with advanced switched capacitor (SC) techniques, a plurality of single-switch current-balancing circuits is developed to drive multiple light-emitting diode (LED) strings in this paper. Compared with the existing current-balancing LED drivers, the proposed drive circuits exhibit their attractive advantages in size and cost efficiency because just one active switch and one magnetic device are required. LED strings' current can be regulated by controlling the duty ratio of the switch in pulsewidth-modulation mode. Both advanced resonant and nonresonant SC methods are introduced to optimize the performance of the proposed LED drivers. The feasibility and theoretical analysis are verified with a 9-W dual-channel nonisolated prototype and a 25-W four-channel isolated prototype.