Estimation of Optical Power and Heat-Dissipation Factor of Low-Power SMD LED as a Function of Injection Current and Ambient Temperature

Optimization of light-emitting diode (LED) design is highly dependent on the relationship between photometric, electric, and thermal parameters of the device. The photoelectrothermal (PET) theory connects all the features of LED device. In this paper, wall-plug efficiency equations of PET theory were extended to estimate heat-dissipation factor and optical power of low-power surface-mounted device (SMD) LED. The wall-plug efficiency as a function of ambient temperature and injection current is used to predict the heat-dissipation factor and the optical power of the SMD LED. The TeraLED and T3ster systems were utilized to provide optical and thermal test reports of the LED parameters at a certain range of injection current and ambient temperature. The presented equations were verified by testing on low-power SMD LED. Results demonstrate that the estimated and measured values were in good agreement for all the considered parameters. This validates the extension of PET theory equations for low-power SMD LED.