A More Efficient PFC Single-Coupled-Inductor Multiple-Output Electrolytic Capacitor-Less LED Driver With Energy-Flow-Path Optimization

In order to match the long life span of light emitting diodes (LEDs), electrolytic capacitor-less off-line LED drivers have been intensely developed. However, the relatively low power efficiency is a common issue for many electrolytic capacitor-less designs. In this paper, a more efficient single-coupled-inductor multiple-output (SIMO) LED driver is proposed. The electrolytic capacitor-less design is targeted for lighting applications with color mixing and color temperature adjustment, where a small capacitance actively balances the power difference between the ac input and multiple dc outputs. Using energy-flow-path optimization, the proposed LED driver has some direct and efficient energy flow paths. In particular, additional energy flow paths are implemented, connecting directly from the small capacitance to multiple dc outputs. Thus, the overall power efficiency is improved. Furthermore, the proposed LED driver is designed with a carrier-based control without the high-precision current sensor for the single-coupled inductor, and thus simpler signal sampling and reduced control complexity can be achieved for independent regulations of multiple dc outputs.