Prediction of junction temperature of high-voltage white LED based on relative chromaticity parameters

With the improvement of the market's requirements on the color rendering of high-voltage LED light sources, accurately predicting the junction temperature of high-voltage LED, preventing led aging and extending the service life have become a topic worth studying. In this paper, the relationship between the junction temperature and the chromaticity parameters, and the relationship between the chromaticity parameters and the driving current are respectively studied for the blue excited yellow phosphor type high-voltage white LED. Finally, the functional relationship among the junction temperature, the chromaticity parameters and the driving current is established. To further accurately predict the junction temperature of the high-voltage LED. Subtracting the color fidelity R_f and color gamut R_g of the initial state from the color fidelity and color gamut at the measurement temperature to obtain the relative chromaticity parameters ∆R_f, ∆R_g can eliminate the self heating effect of the current; subtracting the initial temperature T_j from the measured temperature to obtain the relative junction temperature ∆T_j can eliminate the temperature deviations introduced by the high temperature chamber. The functional relationship among the relative junction temperature ∆T_j and the relative chromaticity parameters ∆R_f, ∆R_g fitting curve are obtained. For 12V and 6V high-voltage LEDs with the same power, the linearities of the fitting functions of ∆T_j-∆R_f and ∆T_j− ∆R_g are close to one. Compared with the results measured by T3ster, the maximum errors of junction temperature prediction based on color fidelity and color gamut are 3.33% and 4.24% respectively, which are within the acceptable range. It shows that these methods are entirely feasible and has particular practical value.