High-Efficient Electrolytic-Capacitor-less Off-Line LED Driver with Reduced Power Processing

Abstract

In this paper, an integrated parallel buck-boost and boost converter (IPB3C) is proposed as an electrolytic-capacitor-less LED driver. The IPB3C ensures high PF and low 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. The boost converter is employed to cancel the low-frequency ripple at the LED. In return, this decreases the flicker effect and only a relatively small capacitance is needed. The buck-boost converter handles the full power of the LED, while the boost converter handles only a portion of the LED power. Thus, better efficiency is ensured compared to 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 IPB3C is analyzed, and its design methodology is presented. A prototype of the proposed converter supplying an LED lamp of 108 V/ 0.35 A is presented. The prototype shows high PF, very small THD, output voltage ripple of 4.5 %, output current ripple of 19 %, and high efficiency of 92.4 %.