You, J.P., Tran, N.T., Lin, YC. et al. Journal of Elec Materi (2009) 38: 761. doi:10.1007/s11664-009-0754-y
Phosphor-concentration-dependent characteristics of white light-emitting diodes (LEDs) under different current regulation conditions were investigated. It is found that the phosphor conversion efficiency of white LEDs driven under constant current is lower than that under pulse current. In addition, white LEDs driven under constant current exhibit higher junction temperature than under pulse current, and the difference is phosphor concentration dependent. For both pulse and constant current modes, white LEDs show relatively stable optical characteristics at relatively higher drive currents, when relatively higher phosphor concentrations are used. At relatively higher phosphor concentrations, the correlated color temperature and the chromaticity coordinates have also been observed to be relatively stable for white LEDs in both constant and pulse current modes.
Light-emitting diodes phosphor current regulation junction temperature