The influence of mutual thermal interactions between power LEDs on their characteristics

The paper concerns the influence of thermal phenomena on the characteristics of power LEDs. The electrothermal model of the power LED for the SPICE software taking into account electric, thermal and optical properties of the considered devices, and particularly the mutual thermal coupling between the devices situated on the common heat-sink or in the LED module, is presented. Using the worked out model the current-voltage characteristics of the selected diodes, dependences of their junction temperature on the forward current and the illuminance of the area lighted by the investigated LED on its forward current are calculated. These characteristics were calculated at different cooling conditions of the investigated LED, and the results of calculations were compared with the results of measurements. The single diode, two diodes situated on the common heat-sink, and the LED module are considered. The good agreement between the results of calculations and measurements confirms the correctness of the worked out model.