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.