A Novel Quasi-Single-Stage Boost-LLC AC/DC Converter With Integrated Boost Cells for Achieving Low Bus Voltage for LED Driver

In this article, a novel quasi-single-stage Boost- LLC ac/dc converter with integrated Boost cells for an LED driver is proposed. The Boost stage is consisted of two integrated Boost cells which share a storage capacitor and the switches with an LLC resonant converter. Only the LLC resonant converter is regulated to obtain a constant output current. One node of the bus capacitor is connected to a stable electric potential, which makes this converter not suffer from the common mode noise problem. A high power factor (PF) can be achieved with the operation of Boost stage, while the bus voltage is low under high input voltage. Soft-switching can be easily realized for the switches and high efficiency can be achieved. Detailed theoretical analysis has been presented. Detailed design considerations and design process have been presented. A 78 V/1. 32 A prototype with 180– 260V ₀₂ input is developed to verify the theoretical analysis. Experimental results show that the prototype can obtain PF >0. 98 and bus voltage < 410 V within the entire input voltage range at full load. The full load efficiency is always over 91%.