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

Abstract

In this article, a novel quasi-single-stage Boost- <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LLC</i> 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 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LLC</i> resonant converter. Only the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LLC</i> 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– <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$260V_{\mathrm {ac}}$ </tex-math></inline-formula> 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%.