Optimized semi-sphere lens design for high power LED package

Abstract

In recent years, high power light emitting diodes (LEDs) have played a very important role in many fields such as LED TV back light or white LED illumination. However, most of past LED package researches have focused on the directivity of LED units; the issue of the extraction efficiency usually has been investigated limited to the chip level, but no much attention paid at the package level. However, this should be a very important topic especially for today’s high power LED output demand as we believe. In this work, utilizing a simulation tool, we show how the geometry of the package affects the efficiency of chip’s output power. An optimized semi-sphere package is proposed, which can improve the efficiency by a factor of 23% compared with the traditional cylinder package. Even considering a needed directivity (e.g. 2θ1/2=24°) for some specific applications, the semi-sphere module can still have 17% output power more than that of a domed cylinder package. These results are very valuable and can be used as a reference guide for the design of the high power LED package.