Interleaved Buck Converter for Fast PWM Dimming of High-Brightness LEDs

The goal of this paper is the evaluation of the interleaved buck converter as a high-brightness (HB) LEDs electronic driver, comparing its performance with the standard buck converter. 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 application 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 output current ripple with much smaller inductances, thus allowing PWM dimming at higher frequencies (20 kHz and beyond), avoiding 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.