GaN-Based High-Power-Density Electrolytic-Free Universal Input LED Driver

Abstract

This paper presents a high-power-density high-power-factor GaN-based two-stage electrolytic-free offline LED driver. The LED driver achieves high power density through the use of a hybrid film-ceramic stacked switched capacitor (SSC) energy buffer, and a comprehensive optimization methodology that evaluates various converter topologies and designs and minimizes overall system volume while maintaining high efficiency. Based on this optimization approach, a totem-pole bridgeless boost power factor correction (PFC) converter is selected for the first stage, while a stacked-input isolated LLC dc-dc converter is selected for the second stage. The optimization procedure also minimizes the passive volume of the SSC energy buffer incorporating the volumetric energy density of commercially available capacitors. The optimized SSC energy buffer utilized in the proposed LED driver has 50% less passive volume than a capacitor-only solution. A 600-W prototype LED driver designed using the proposed approach for universal input voltage (90 - 305 V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">rms</sub> ) and 24-V output voltage is built and tested. The PFC stage achieves a peak efficiency of 98% while the LLC stage achieves a peak efficiency of 95%. The prototyped LED driver achieves a power density of 28 W/in <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> .