A 220-V AC, LUT-controlled 6-segmented LED driver with background calibration

摘要

This paper presents an AC-powered, boost-converter-based multi-segmented LED driver that maintains a high-power factor (PF) and accurate input current level, using a novel look-up table (LUT)-based digital control with background calibration and optimal switching mode selection schemes. The presented multi-segmented LED driver aims to reduce the costs of high-voltage capacitors and high-inductance inductor by segmenting the load LEDs into multiple strings and switching the number of LED strings connected in series for line regulation and power-factor correction. However, the increased number of power switches calls for a sophisticated control scheme that responds quickly to the switching mode changes and adapts properly to the operating condition changes. The presented LED driver addresses this by employing an LUT that can provide a pre-programmed, arbitrarily fast response to the periodic 220-V AC input, supplemented by a periodic background calibration and optimal switching mode selection to track any unexpected changes in the input, load, and environment conditions. A prototype 220-V AC LED driver with 6-segment LED strings demonstrates a 98.4% power factor (PF), 91% conversion efficiency, 26 mA_rms input current error, and 67% reduction of discrete component costs while delivering 38.3 W to the load.