Optical analysis and measurements of high-power COP LED packages

Abstract

The purpose of this study is to investigate the optical behaviors and thus maximize luminous efficiency (focusing on light extraction efficiency here) of high-power chip-on-plate (COP) LED packages with the low-cost feature. First of all, to validate the luminous flux and candela distribution measurements and TracePro (one of commercial optical software) simulation, a Lumiled K1 LED package (one of commercially-available packages) is analyzed numerically and experimentally and compared with given data sheet. After the validation, both measurements and TracePro are applied to studying the candela distribution and light extraction efficiency of the COP LED packages. Furthermore, parametric studies of lens cavity height-radius ratio (h/r) and cup angle of COP LED packages using TracePro are implemented to find out the key factors to the light extraction efficiency. The results show that the candela distribution of COP LED packages from TracePro simulation is consistent with that from experiments. In optical parametric study, the effect of lens cavity height-radius ratio (h/r) of the COP LED packages on light extraction is found to be negligible, except for h/r=0. Moreover, with given lens cavity, the effect of air gap between silicone encapsulant and lens on light extraction is apparent by a way that air gap decreases with increasing light extraction. Also, it is found that the cup angle below 60° does not apparently affect light extraction, but beyond 60°, light extraction increases with the cup angle.