A modified bidirectional thermal resistance model for junction and phosphor temperature estimation in phosphor-converted light-emitting diodes

Besides the junction temperature, phosphor temperature is another key parameter to characterize the thermal behavior of phosphor-converted light-emitting diodes (pc-LEDs). However, the measurement of phosphor temperature remains a challenge. In this paper, we proposed a modified bidirectional thermal resistance model for the junction and phosphor temperature estimation. Compared with the conventional thermal resistance model, both the heat generation of the phosphor layer and the heat flow through the phosphor layer were further considered in this model. Three LED packaging structures were fabricated and measured to complete the model. The heat generation of the chip and phosphor layer was measured. With varying driving current from 0.05 A to 0.65 A with an increment of 0.1 A, the maximum deviation of the predicted and measured junction and phosphor temperature is less than 1% and 9.2%, respectively, which proves the feasibility of the proposed model for the junction and phosphor temperature estimation.