Color Temperature Tunable White LED Cluster With Color Rendering Index Above 98

A photometric optimization model for correlated color temperature (CCT) tunable white LED clusters, including down-conversion energy loss, was developed under the constraint of color rendering index (CRI). The CCT tunable R/Y/C white LED cluster, which consists of direct-emission red LEDs, phosphor-coated yellow LEDs (pc-Y LEDs) with green and orange phosphors excited by a blue chip, and pc-C LEDs with green phosphors excited by a blue chip, was obtained under conditions of both CRI and special CRI of R9 for strong red above 98 at CCTs from 2700 to 6500 K. The optimal peak wavelengths of red LED, blue chip, green and orange phosphors, and optimal pc-Y LED as well as pc-C LED are presented. A CCT tunable R/Y/C white LED cluster with CRIs of 97-99, R9s of 98-99, CQSs of 95-97, and LEs of 122-132 lm/W was realized at CCTs from 2731 to 6533 K, which could become an ideal light source for application as Planck's blackbody radiator or daylight source.