Evaluation of a Synchronous Flyback Driving Parallelized High Efficiency LEDs

In this paper, parallel connection of high efficiency LEDs for lighting applications is studied. Unlike series connection, parallel connection of LEDs allows the operation of these devices at different current levels. Among other features, this allows the operation of the remaining LEDs if one of them fails. The main drawback of parallel connection is, as is very well known, current equalization and stable operation, due to the V vs. I characteristic of the LED. An active equalization and current limitation with MOSFETs is studied and implemented, thus obtaining a high current-low voltage power load. To supply this load, a 16 W synchronous flyback is used, in order to supply 4 high efficiency LEDs. The overall prototype design and construction is discussed, and electrical and light measurements are presented.

[1]  P. Wood,et al.  Synchronous rectifiers versus Schottky diodes: a comparison of the losses of a synchronous rectifier versus the losses of a Schottky diode rectifier , 1994, Proceedings of 1994 IEEE Applied Power Electronics Conference and Exposition - ASPEC'94.

[2]  N. Narendran,et al.  Life of LED-based white light sources , 2005, Journal of Display Technology.

[3]  M. Wendt,et al.  LEDs in Real Lighting Applications: from Niche Markets to General Lighting , 2006, Conference Record of the 2006 IEEE Industry Applications Conference Forty-First IAS Annual Meeting.

[4]  A.J. Calleja,et al.  Using Tapped-Inductor Converters as LED Drivers , 2006, Conference Record of the 2006 IEEE Industry Applications Conference Forty-First IAS Annual Meeting.

[5]  A.J. Calleja,et al.  Evaluation of a high efficiency boost stage to supply a permanent LED emergency lighting system , 2004, Conference Record of the 2004 IEEE Industry Applications Conference, 2004. 39th IAS Annual Meeting..

[6]  J. M. Alonso,et al.  Evaluation of a low cost permanent emergency lighting system based on high efficiency LEDs , 2003 .

[7]  A.J. Calleja,et al.  Driver for high efficiency LED based on flyback stage with current mode control for emergency lighting system , 2004, Conference Record of the 2004 IEEE Industry Applications Conference, 2004. 39th IAS Annual Meeting..

[8]  M.M. Hernando,et al.  New self-driven synchronous rectification system for converters with a symmetrically driven transformer , 2005, IEEE Transactions on Industry Applications.