Muna E. Raypah

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.

Estimation of Luminous Flux and Luminous Efficacy of Low-Power SMD LED as a Function of Injection Current and Ambient Temperature

Light-emitting diode (LED) luminous flux and efficacy as a function of temperature and current is important to qualify and optimize the design of an LED system. In this paper, the extension of light output equation was used to estimate luminous flux and efficacy of low-power surface-mounted device LED. The photometric and thermal test reports of LED parameters at a certain range of injection current and ambient temperature were obtained by the combination of T3ster and TeraLED systems. The luminous flux and efficacy as a function of injection current and ambient temperature were predicted. The agreement between the experimental and theoretical results validates the extended equation used in this paper. The optimized operating conditions of LED under test are determined.

Modeling Spectra of Low-Power SMD LEDs as a Function of Ambient Temperature

The information of spectral changes with various parameters is a key for optimizing the performance and thus improving long-term reliability of light-emitting diodes (LEDs) in solid-state lighting applications. In this paper, the extension of spectrum model was used to estimate the spectral flux of indium gallium aluminum phosphide (InGaAlP)-based low-power surface-mounted device (SMD) LEDs. The spectra and photometric parameters of LED packages were measured at several ambient temperatures to test the spectrum model extension. The spectrum model is constructed at 298 K to predict the spectral fluxes of the LED at any ambient temperature. Carrier temperature, peak frequency, and bandgap energy variations with ambient temperature are included in this extension. The agreement between the measured and theoretical results of spectrum, luminous flux, and International Commission on Illumination (CIE) color coordinates validates the extended spectral model for low-power LEDs.

Influence of injection current and ambient temperature on intensity and wavelength of low-power SMD LED

Low power surface-mounted (SMD) LEDs are paid much attention in research and development due to their portability and miniaturization. Optical characteristics of SMD LEDs have to maintain more accurate specifications in signaling applications such as traffic lights or railway. Current and temperature stabilization is important for attaining constant spectral properties of SMD LEDs. In this manuscript, the effect of change in ambient temperature and injection current on SMD LED intensity and wavelength shift is reported. Measurements were carried out using a spectrometer to record the LED optical parameters at various operating conditions. Detailed analyses show that the ambient temperature has a significant influence on optical characteristics of low-power SMD LED. The investigation of LED optical behaviors helps in choosing the appropriate working condition at the optimum level.

Influence of thermal interface material on thermal performance of InGaAlP thin-film SMD LED mounted on different substrate packages

Purpose Proper thermal management is a key to improve the efficiency and reliability of light-emitting diodes (LEDs). This paper aims to report the influence of applying thermally conductive materials on thermal performance of indium gallium aluminum phosphide (InGaAlP)-based thin-film surface-mounted device (SMD) LED. Design/methodology/approach The LED thermal and optical parameters were determined using the combination of thermal transient tester (T3Ster) and thermal and radiometric characterization of power LEDs (TeraLED) instruments. The LED was mounted on FR4, 2W and 5W aluminum (Al) package substrates. Measurements were carried out by setting different boundary conditions: air between LED package and substrate and using thermally conductive epoxy (TIM A) and adhesive (TIM B) of thermal conductivity 1.67 and 1.78 W/mK, respectively. Findings For LED mounted on FR4 package, the total real thermal resistance is improved because of TIM B by 6 and 9 per cent at 50 and 100 mA, respectively. Likewise, the relative decrease in total thermal resistance of LED on 2W Al package is about 9 and 11 per cent. As well, for LED mounted on 5W Al package, the total real thermal resistance is reduced by 2 and 4 per cent. Originality/value No much work can be found in the literature on thermal interface material effects on thermal performance of low-power SMD LED. This work can assist in thermal management of low-power LEDs.