IEEE TRANSACTIONS ON POWER ELECTRONICS, VOL. 26, NO. 9, SEPTEMBER 2011 2627 Interleaved Buck Converter for Fast PWM Dimming of High-Brightness LEDs Jorge Garcia, Member, IEEE, Antonio J. Calleja, Member, IEEE, Emilio L ´ opez Corominas, Member, IEEE, David Gacio Vaquero, Student Member, IEEE, and Lidia Campa, Student Member, IEEE Abstract—The goal of this paper is the evaluation of the inter- leaved buck converter as a high-brightness (HB) LEDs electronic driver, comparing its performance with the standard buck con- verter. The main drawbacks of the standard converter come from the high inductor value necessary to guarantee low output current ripple, which result in high inductor losses and rough switching waveforms at the semiconductors. Additionally, when the applica- tion demands pulsewidth modulation (PWM) dimming, this high inductance value yields to a relatively low dimming frequency that can result in audible noise problems due to several phenomena as magnetostrictive effects at the inductors or piezoelectric effects at the capacitors. The proposed interleaved converter obtains low out- put current ripple with much smaller inductances, thus allowing PWM dimming at higher frequencies (20 kHz and beyond), avoid- ing audible noise. Moreover, such low inductances, along with the triangular waveforms obtained with the proposed control method, yield to a higher efficiency than in the standard converter. After reviewing the main operation concept of the interleaved converter, a full design process is particularized for driving HB LEDs. A full-dimming range experimental setup has been built and tested, and experimental results are shown and discussed, compared with those obtained for the standard converter. Index Terms—High-brightness (HB) LED drivers, interleaved converters, lighting electronics. I. INTRODUCTION A T PRESENT, some of the most important strategic efforts in research are the increasing efficiency of power systems and the enhanced control strategies that allow a more ratio- nal use of the energy, as well as an increase in power savings. In this scenery, major advances have been carried out recently in lighting systems, at the level of improved efficiency light sources (solid-state lighting and high-intensity discharge (HID) lamps) [1]–[6], as well as in power topologies and schemes (customizing of existing systems, durability and reliability is- sues, etc.) [7]–[15] or control strategies (smart systems, digital control, etc.) [14]–[26]. Manuscript received December 3, 2010; revised January 17, 2011; accepted February 18, 2011. Date of current version September 16, 2011. This work was supported by the Spanish Government, Innovation and Science Office (MCINN), under Research Grant DPI-2007–61522, project “BENAPI,” and by the Euro- pean Union through the ERFD Structural Funds [Fondo Europeo de Desar- rollo Regional (FEDER)]. Recommended for publication by Associate Editor M. Ponce-Silva. The authors are with the Department of Electrical Engineering, ce3i2 Research Group, University of Oviedo, Asturias 33204, Spain (e-mail: garciajorge@uniovi.es; calleja@uniovi.es; elopezc@uniovi.es; gaciodavid@ uniovi.es; campalidia@uniovi.es). Digital Object Identifier 10.1109/TPEL.2011.2121922 Fig. 1. AM dimming (a) and PWM dimming (b) schemes for HB-LEDs supply. High-brightness (HB) LEDs outstand currently as the artifi- cial light source, which withstands a higher rate of sustained luminous efficiency increase. Such characteristic, along with their high operating life and reliability, turn them into the first choice for an increasing number of applications, as automotive, emergency, backlight, indoor, etc., [6], [14], [17], [27]–[32]. As it is well known, these devices need a current limiting driver to ensure proper operation, usually implemented by means of power electronic stages based on switch-mode power supplies. The avoidance of the use of electrolytic capacitors is one of the most important tasks in the development of electronic LED drivers [2], [18], [33]–[37]. As the operating life of the electrolytic capacitor is smaller than the life of any other part of the driver, the avoidance of such devices increases the reliability of the whole system. Another hot topic related to LED driver design is the capabil- ity of output light regulation, called dimming. The adjusting of the output light level to the level required results in high power savings, thus resulting in a more rational use of the energy. If the application does not require high luminous quality (pub- lic lighting, emergency lighting, etc.), this regulation can be car- ried out adjusting the output dc current level through the LEDs. This light control scheme is called AM dimming [see Fig. 1(a)]. The application must assume that some spectral slide will ap- pear due the different operation point of the LEDs at different output levels; Also, at very low dimming levels (typically 20% and below), the equivalent parameters of the LEDs can turn unstable, and hence, light variations appear. However, if the light emitted spectrum is critical for that appli- cation [(backlight, red-green-blue color model (RGB) systems, 0885-8993/$26.00 © 2011 IEEE