Thermal Analysis of the Factors Influencing Junction Temperature of LED Panel Sources

Baran, Krzysztof; Różowicz, A.; Wachta, H.; Różowicz, Sebastian

doi:10.3390/en12203941

Cited by 21 publications

(13 citation statements)

References 31 publications

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“…The glass-epoxy based laminate FR4 is made of an upper copper layer that comprises a conductive path and a dielectric layer that is glass fiber with epoxy resin (FR4). The MCPCB is usually made of three material layers which are aluminum, a thin dielectric layer and copper (Baran et al , 2019). The thermal conductivity of the MCPCB is considered the thermal conductivity of its dielectric layer.…”

Section: Methodsmentioning

confidence: 99%

Enhancement of luminous flux of InGaAlP-based low-power SMD LEDs using substrates with different thermal resistances

Raypah

Mahmud

Devarajan³

2020

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Purpose Optimization of light-emitting diodes’ (LEDs’) design together with long-term reliability is directly correlated with their photometric, electric and thermal characteristics. For a given thermal layout of the LED system, the maximum luminous flux occurs at an optimal electrical input power and can be determined using a photo-electro-thermal (PET) theory. The purpose of this study is to extend the application of the luminous flux equation in PET theory for low-power (LP) LEDs. Design/methodology/approach LP surface-mounted device LEDs were mounted on substrates of different thermal resistances. Three LEDs were attached to substrates which were flame-retardant fiberglass epoxy (FR4) and two aluminum-based metal core printed circuit boards (MCPCBs) with thermal conductivities of about 1.0 W/m.K, 2.0 W/m.K and 5.0 W/m.K, respectively. The conjunction of thermal transient tester and thermal and radiometric characterization of LEDs system was used to measure the thermal and optical parameters of the LEDs at a certain range of input current and temperature. Findings The validation of the extended application of the luminous flux equation was confirmed via a good agreement between the practical and theoretical results. The outcomes show that the optimum luminous flux is 25.51, 31.91 and 37.01 lm for the LEDs on the FR4 and the two MCPCBs, respectively. Accordingly, the stipulated maximum electrical input power in the LED datasheet (0.185 W) is shifted to 0.6284, 0.6963 and 0.8838 W between the three substrates. Originality/value Using a large number of LP LEDs is preferred than high-power (HP) LEDs for the same system power to augment the heat transfer and provide a higher luminous flux. The PET theory equations have been applied to HP LEDs using heatsinks with various thermal resistances. In this work, the PET theory luminous flux equation was extended to be used for Indium Gallium Aluminum Phosphide LP LEDs attached to the substrates with dissimilar thermal resistances.

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Section: Methodsmentioning

confidence: 99%

Enhancement of luminous flux of InGaAlP-based low-power SMD LEDs using substrates with different thermal resistances

Raypah

Mahmud

Devarajan³

2020

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“…It should be stressed that since the polynomials in the above approximations contain an integer of s, the inverse transform can be determined by standard methods [35,36]. Figure 8 presents the electrical circuit with fractional-order magnetic coupling between two coils.…”

Section: Of 16mentioning

confidence: 99%

Properties of Fractional-Order Magnetic Coupling

et al. 2020

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This paper presents the properties of fractional-order magnetic coupling. The difficulties connected with the analysis of two coils in dynamic states, resulting from the classical approach, provided motivation for studying the properties of fractional-order magnetic coupling. These difficulties arise from failure to comply with the commutation laws, i.e., a sudden power disappearance in the primary winding caused by a switch-mode power supply. Theoretically, under ideal conditions, a sudden power disappearance in the coil is, according to the classical method, manifested by a sudden voltage surge in the form of the Dirac delta function. As is well-known, it is difficult to obtain such ideal conditions in practice; the time of current disappearance does not equal zero due to the circuit breaker’s imperfection (even when electronic circuit breakers are used, the time equals several hundred nanoseconds). Furthermore, it is necessary to take into account phenomena occurring in real inductances, such as the skin effect, the influence of the ferromagnetic core and many other factors. It would be very difficult to model all these phenomena using classical differential calculus. The application of fractional-order differential calculus makes it possible to model them in a simple way by appropriate selection of coefficients and fractional-order derivatives. It should be mentioned that the analysis could be used, for example, in the case of high-voltage generation systems, including spark ignition systems of internal combustion engines. The use of fractional-order differential calculus will allow for more accurate modeling of phenomena occurring in such systems.

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“…According to most scientific publications, the optical efficiency of LED sources is 30%, which means that 70% of the power is heat loss [16][17][18][19][20][21]. In a small number of publications, the research results indicate that, for the latest LED sources, the above value of optical efficiency may be higher [22,23]. In addition, the increasingly higher power of LED sources and the small chip area result in high values of thermal density and obstruct effective heat abstraction to the environment.…”

Section: Introductionmentioning

confidence: 99%

Modeling of Selected Lighting Parameters of LED Panel

et al. 2020

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Semiconductor light sources are currently the fastest growing and most energy efficient group of light sources used in lighting technology. Their lighting parameters, such as luminous flux, correlated color temperature and color rendering index depend on the value of the forward current, as well as the temperature of the junction. LED source manufacturers usually specify, in data sheets, the effect of junction temperature and forward current on the luminous flux for individual light sources. The difficulty, however, is the correct determination of temperature and then lighting parameters, by simulation methods for multi-source lighting systems. Determining the junction temperature which affects lighting parameters is particulary important in the case of LED panels and luminaires, where thermally coupled LED sources shaping the output lighting parameters are in close proximity to each other. Additionally, other factors influencing the temperature distribution of sources, such as the design and geometry of the cooling system, the design of the printed circuit and thermal interface material used, should be considered. The article is a continuation of the publication in this journal where the influence of factors influencing the temperature distribution of the LED panel is presented. The purpose of the research in this article was to confirm the possibility of using CFD (Computational Fluid Dynamics) software, as well as to determine the accuracy of the results obtained in the temperature analysis of the multi-source LED panel, and in determining the output lighting parameters of the LED panel based on it. In this article, based on previously published research, a LED panel model with a cooling system was made, and then the CFD software determined the junction temperature of all light sources. The determined temperature of the LED sources constituted the basis for determining the output lighting parameters of the panel: luminous flux, color temperature and color rendering index. The simulation results were verified by real measurements on the constructed LED panel prototype. The LED panel temperature difference between the simulation results and the real results on the prototype did not exceed 5%. Moreover, the error of lighting parameters between the simulation results obtained and the results on the LED panel prototype in the worst case was 4.36%, which proves the validity and accuracy of simulation studies.

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Thermal Analysis of the Factors Influencing Junction Temperature of LED Panel Sources

Cited by 21 publications

References 31 publications

Enhancement of luminous flux of InGaAlP-based low-power SMD LEDs using substrates with different thermal resistances

Enhancement of luminous flux of InGaAlP-based low-power SMD LEDs using substrates with different thermal resistances

Properties of Fractional-Order Magnetic Coupling

Modeling of Selected Lighting Parameters of LED Panel

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