Electrolytic-Capacitor-less Off-Line LED Driver based on Integrated Parallel Buck-Boost and Boost Converter

Abstract

In this paper, an integrated parallel buck-boost and boost converter (IPB <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> C) is proposed as an electrolytic-capacitorless light-emitting diode (LED) driver. The IPB <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> C offers high power factor (PF) and low total harmonic distortion (THD). The driver is composed of two converters that are connected in parallel, using just one controlled switch. The buck-boost duty is to deliver constant power to the LED, while ensuring a good PF. Concerning the boost converter, it is employed to cancel the low frequency ripple at the output of the converter and the LED. In return, this will decrease the flicker effect and only a relatively small capacitance will be needed in order to fulfil the standards. The buck-boost converter handles the full power of the LED, while the boost converter handles a portion of the LED full power. Thus, better efficiency is ensured by this parallel configuration compared to the conventional cascaded integrated converters. Moreover, the voltage across the switch is low, as it is the higher of buck-boost or boost converter, but not the addition of both. In this paper, the IPB <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> C is analyzed, and its design methodology is presented. In addition, the paper presents a simulation verification for the proposed converter supplying an LED luminaire of 46 V/ 0.575 A. The simulation shows a high PF nearly equal to one, very small THD of nearly zero, output current ripple of 9 %, using two capacitors of only 2 μF and 47 μF.