This paper presents a light-emitting-diode (LED) model based on the four-parameter Taylor series to describe the V-I characteristic of the LED at different junction temperatures. Therefore, in order to precisely model the LED non-linear characteristics at different junction temperatures, an improved Taylor series based LED model is proposed according to the four available parameters: maximum operating point, rated operating point, knee point, and temperature coefficient obtained from LED V-I curves. Furthermore, in order to perform the DC and small-signal simulation and analyses of LED drivers at different junction temperatures, the proposed model can be used to derive the LED DC and small-signal equivalent resistances at different junction temperatures. Finally, the measured results are compared with the modeled V-I curves, DC equivalent resistances, and small-signal equivalent resistances of the experimental LED at different junction temperatures. Index Terms-AC Model, DC Model, Equivalent circuit model, Light-emitting-diode, Modeling, Temperature coefficient, Taylor series expression.

Thispaper presents an Organic-Light-Emitting-Diode (OLED) equivalent circuit model with temperature coefficient and intrinsic capacitor. In order to precisely describe the OLED non-linear V-I characteristics at different junction temperatures, four parameters: maximum operating point, rated operating point, knee point, and temperature coefficient, are obtained from the OLED V-I curves to establish the improved Taylor series based OLED model. Furthermore, in order to perform the transient and AC simulations of the OLED drivers, the proposed model can be used to generate the V-I look-up table for the voltage-controlled-piecewise-linear (VPWL) behavior model for the time-domain and frequency-domain circuit simulations. Besides, the intrinsic capacitor of the OLED is voltage dependent and can be modeled with the piecewise-linear (PWL) behavior model to associate with the built VPWL behaviormodel for the OLED circuit simulations. Finally, the measured results are provided to compare with the modeled V-I curves, transient simulations, and AC simulations of the OLED. Index Terms-AC Model, DC Model, Equivalent circuit Model, Organic-Light-emitting-diode, OLED, Modeling, Temperature coefficient, Taylor series expression.I.