Determining Phosphor Temperature in Light-Emitting Diode Based on Divisional Normalized Emission Power

We propose a non-contact method for determining phosphor/silicone temperature (phosphor temperature) in phosphor-coated light-emitting diode (pc-LED). The pc-LED with a surface mounted device (SMD) structure is primarily consisted of InGaN/GaN blue LED chip, (Sr,Ca)AlSiN3:Eu
²⁺
red rare-earth phosphor, and transparent dimethyl silicone. This proposed method is basically based on a linear temperature dependence of divisional normalized emission power for phosphor/silicone mixture. Four types of pc-LED corresponding to four different phosphor concentrations are examined by proposed method. A comparison of measured results between micro-thermocouple device and proposed method has also been carried out, showing a fairly good agreement between them, except for pc-LED with 4.8 wt% phosphor concentration. We suggest that this proposed method can provide a useful tool for further study of optical and thermal characteristics in pc-LED.