The effects of temperature and driving current on the key parameters of commercially available, high-power, white LEDs

Yurtseven, M. Berker; Mete, Seher; Onaygıl, Sermin

doi:10.1177/1477153515576785

Cited by 23 publications

(7 citation statements)

References 6 publications

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“…where: P H -heat power, η o -optical efficiency and P e -electrical power. Currently, in many references the optical efficiency of LED sources η o is declared to be at the level of 15-35% [29][30][31][32][33][34]; one can, however, encounter certain references where the efficiency η o is a bit higher, reaching up to 45%, depending on the LED source model and I F forward current used [35].…”

Section: Figurementioning

confidence: 99%

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

et al. 2019

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Limiting junction temperature T j and maintaining its low value is crucial for the lifetime and reliability of semi-conductive light sources. Obtaining the lowest possible temperature of T j is especially important in the case of LED panels, where in a short distance there are many light sources installed, between which there occurs mutual thermal coupling. The article presents results of simulation studies connected with the influence of construction and ambient factors that influence the value of junction temperature of exemplary LED panel sources. The influence of radiator's construction, printed circuit boards, as well as the influence of ambient factors, such as ambient temperature T a and air flow velocity v were subjected to the analysis. Numerical calculations were done in the FloEFD software of the Mentor Graphics company, which is based on computational fluid dynamics (CFD). For construction of the LED thermal panel model the optical efficiency η o and real thermal resistance Rth j-c were determined in a laboratory for the applied light sources.

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Section: Figurementioning

confidence: 99%

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

et al. 2019

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“…If this heat energy is not removed steadily, the temperature of the structure increases. LED properties such as luminous flux, luminous efficacy, and efficiency are adversely affected from the increasing temperature [5]. The lifetime of an LED is also dependent on the temperature [6].…”

Section: Introductionmentioning

confidence: 99%

Energy Effıcıent Human Centered Offıce Lıghtıng: A Case Study on Open Plan Offıce wıth Absent Access to Daylıght

Aliparast,

Onaygil

2023

L&E

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Our daily behaviours and physiological functions are regulated by the brain’s central biological clock. Consistent exposure to bright days and dim nights is crucial for aligning these rhythms. Since we spend much time indoors, electrical lighting is often relied upon to sync our circadian rhythms. A challenge in promoting circadian entrainment through electrical lighting is the lack of a standardized test for assessing how effectively lighting luminaires provide circadian-effective light to occupants. This study introduces a case study, optimum suspended height (OSH), measuring luminaire efficiency in achieving a circadian stimulus criterion (CS: 0.3) and equivalent melanopic illuminance in lx (EML: 240) for 38 office workers, based on performance and comfort criteria. The paper outlines OSH application to individual linear luminaire type, including suspended-mounted fixtures. In this field study, tests were conducted to explore how indoor lighting affects occupants’ cognitive performance and visual perception. Linear suspended LED luminaires (LSL) were installed in an open-plan office at Istanbul Technical University (ITU), where office workers were exposed to different heights of lighting conditions. They took visual attention tests and assessed proofreading comfort, with alertness measured using the Karolinska Sleepiness Scale (KSS) test. The study aimed to understand the impact of visual fatigue on cognitive performance and perception with. These initial findings shed light on the relationship between office lighting changes and occupants’ cognitive performance and visual perception.

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“…LED manufacturers usually declare the characteristics of their LEDs at a constant temperature and current in datasheets. However, it is important to know the effects of driving currents and operating temperatures on the LED's luminous flux to attain the desired performance for a specific design of luminaires (Yurtseven et al, 2016). Photoelectro-thermal (PET) theory proved that the maximum luminous flux may not occur at the rated power specified in the LED's datasheet.…”

Section: Introductionmentioning

confidence: 99%

Impact of thermal interface material on luminous flux curve of InGaAlP low-power light-emitting diodes

Raypah

Devarajan

Mahmud

2021

SSMT

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Purpose One major problem in the lighting industry is the thermal management of the devices. Handling of thermal resistance from solder point to the ambiance of the light-emitting diode (LED) package is linked to the external thermal management that includes a selection of the cooling mode, design of heatsink/substrate and thermal interface material (TIM). Among the significant factors that increase the light output of the of the LED system are efficient substrate and TIM. In this work, the influence of TIM on the luminous flux performance of commercial indium gallium aluminium phosphide (InGaAlP) low-power (LP) LEDs was investigated. Design/methodology/approach One batch of LEDs was mounted directly onto substrates which were glass-reinforced epoxy (FR4) and aluminium-based metal-core printed circuit boards (MCPCBs) with a dielectric layer of different thermal conductivities. Another batch of LEDs was prepared in a similar way, but a layer of TIM was embedded between the LED package and substrate. The TIMs were thermally conductive epoxy (TCE) and thermally conductive adhesive (TCA). The LED parameters were measured by using the integrated system of thermal transient tester (T3Ster) and thermal-radiometric characterization of LEDs at various input currents. Findings With the employment of TIM, the authors found that the LED’s maximum luminous flux was significantly higher than the value mentioned in the LED datasheet, and that a significant reduction in thermal resistance and junction temperature was revealed. The results showed that for a system with low thermal resistance, the maximum luminous flux appeared to occur at a higher power level. It was found that the maximum luminous flux was 24.10, 28.40 and 36.00 lm for the LEDs mounted on the FR4 and two MCPCBs, respectively. After TCA application on the LEDs, the maximum luminous flux values were 32.70, 36.60 and 37.60 lm for the FR4 and MCPCBs, respectively. Moreover, the findings demonstrated that the performance of the LED mounted on the FR4 substrate was more affected by the employment of the TIM than that of MCPCBs. Research limitations/implications One of the major problems in the lighting industry is the thermal management of the device. In many low-power LED applications, the air gap between the two solder pads is not filled up. Heat flow is restricted by the air gap leading to thermal build-up and higher thermal resistance resulting in lower maximum luminous flux. Among the significant factors that increase the light output of the LED system are efficient substrate and TIM. Practical implications The findings in this work can be used as a method to improve thermal management of LP LEDs by applying thermal interface materials that can offer more efficient and brighter LP LEDs. Using aluminium-based substrates can also offer similar benefits. Social implications Users of LP LEDs can benefit from the findings in this work. Brighter automotive lighting (signalling and backlighting) can be achieved, and better automotive lighting can offer better safety for the people on the street, especially during raining and foggy weather. User can also use a lower LED power rating to achieve similar brightness level with LED with higher power rating. Originality/value Better thermal management of commercial LP LEDs was achieved with the employment of thermal interface materials resulting in lower thermal resistance, lower junction temperature and brighter LEDs.

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The effects of temperature and driving current on the key parameters of commercially available, high-power, white LEDs

Cited by 23 publications

References 6 publications

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

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

Energy Effıcıent Human Centered Offıce Lıghtıng: A Case Study on Open Plan Offıce wıth Absent Access to Daylıght

Impact of thermal interface material on luminous flux curve of InGaAlP low-power light-emitting diodes

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