LED Lighting Applications Research Articles

A novel Na2Ca2Si3O9: Tb3+ glass ceramic with high luminescence efficiency and robust thermal stability for white LED lighting application

Given the increasing demand for white light emitting diode (WLED) lighting devices marked by high color rendering indices (CRI) and exceptional thermal stability, there is a burgeoning interest in developing emitters with enhanced performance. Rare earth (RE) ion-activated glass ceramics (GCs) have garnered significant attention due to their outstanding physicochemical and thermal stability, alongside their high luminescence efficiency. In this study, the GCs doped with Tb3+ ions in the Na2O-CaO-SiO2 system matrix were synthesized, incorporating Na2Ca2Si3O9 nanocrystals averaging less than 100 nm in size. Notably, these GC materials demonstrated superior luminescence efficiency in the green light emission under the irradiation of 376 nm light compared to the parent glass. A comprehensive analysis of fluorescence spectra revealed an impressive internal quantum efficiency of 87.34 % for this Tb3+-doped GC. Furthermore, the GC retained 90 % and 84 % of the initial luminescence intensity at 150 °C and 200 °C in comparison to the luminescence level at room temperature, showcasing exceptional resistance to fluorescence thermal quenching. Verification experiments utilized UV LED chip, (Sr, Ca)AlSiN3: Eu2+ red phosphor, BaMgAl10O17: Eu2+ blue phosphor, and Tb3+-doped GC to encapsulate the WLED device, achieving a remarkable CRI of 92, CIE chromaticity coordinates (0.3547, 0.3361), and a correlated color temperature (CCT) of 4550K. In conclusion, the experimental outcomes unequivocally underscore the significant application potential of these Tb3+-doped GCs in the territory of warm WLED lighting.

A Ripple Free Soft-Switched Integrated Series Resonant Converter for Main and Local LED Lighting Application

A Ripple Free Soft-Switched Integrated Series Resonant Converter for Main and Local LED Lighting Application

A Three Leg Asymmetrical Voltage Resonant Converter With Independent Dimming Control for Multiple Load LED Lighting Applications

A Three Leg Asymmetrical Voltage Resonant Converter With Independent Dimming Control for Multiple Load LED Lighting Applications

Considerations on Practical Implementation of Current Source Mode Single-Inductor Multiple-Output LED Driver

There are many possible LED lighting applications where separate regulation of the LED current (luminous flux) of individual LED strings would be desirable—specialized variable correlated color temperature lights for ambient lighting, decorative lighting, surgical lights, horticultural lights, etc. Separate regulation of the current or light flux of individual LED strings is associated with a known problem: the necessity of using a controllable LED driver for each string, which increases the total component count, overall system complexity and costs. One of the possible solutions—a current source mode single-inductor multiple-output LED driver—was discussed in previous different papers. However, the practical implementation of this solution was not discussed in detail. This article aims to correct this omission.

55.3: One‐step extruding method for fabricating perovskite quantum dot light diffusers

All‐inorganic perovskite quantum dots (PQDs) exhibit excellent physics properties and application prospects in the field of LED lighting applications and display devices. However, poor long‐term stability to light irradiation, water, heat, and oxygen hinders the further development of commercialization. Using polymer plastics, such as PS (polystyrene), PC (polycarbonate), PMMA (polymethyl methacrylate), PP (polypropylene), as the matrix along with proper Cs, Pb and halogen (X) sources as perovskite precursors, CsPbX3 PQDs/polymer composites can be synthesized via a solvent‐free and in‐situ polymeric melt encapsulation method. Special attention was paid to the effects of growth conditions on the photoluminescent quantum yield (PLQY) of the composites. The optimized CsPbX3 PQDs/polymer composite demonstrated excellent performance with more than 90% PLQY and 22 nm full width at a halfmaximum (FWHM) for green and 35 nm FWHM for red. Particularly, we combined this in‐situ melting synthesis technology with industrial production, and used a melting extruder to directly fabricate perovskite quantum dot optical diffuser products for backlight display. Under the protection of multi‐layer structure, the PQD diffusers exhibited remarkable long‐term stability. This study provides a novel solvent‐free and in‐situ synthesis route for fabricating diffuser products, which is quite friendly to industrialization and commercialization for perovskite materials.

Study on the application of LED lighting in seedling production of some chryanthemum varieties in Hanoi

Chrysanthemum is a high commercial value plant, which is accounted for a large proportion of the total export of cut flowers in Vietnam. Therefore, the demand for seedling plants is very high. As a short-day plant, chrysanthemum requires supplemental lighting during the 2nd propagation stage in the autumn-winter period. This study aimed to evaluate the applicability of energy-saving LED lights to replace traditional lights in the propagation of some chrysanthemum varieties in Hanoi. The results show that the B3R7 660 nm LED (450 nm blue LED and 660 nm red LED combined in the ratio 7:3) was the most suitable for the 2nd propagation process in the greenhouse of 3 varieties (Pha le Chrysanthemum indicumyellow, Kim cuong C. morifolium cv Kim Cuong and Farm C. morifolium Hibiki). Plants grown under this LED light had a higher shoot multiplication efficiency than those under compact lamps (67.91, 18.47, and 26.89% respectively for Pha le, Kim cuong and Farm). Besides, the quality of seedlings is equivalent to chrysanthemums grown under compact lights. The power-saving efficiency when using LED light was approximate lower 55.21% compared to compact lamps.

Efficient GaN-based hybrid DC-DC converter with simple and low-cost bootstrap gate drivers for LED lighting applications

This paper presents a 40 V-to-8 V GaN-based hybrid DC-DC converter design using 5-to-1 Dickson switched-capacitor structure. The converter, supporting a wide range of output voltage up to the input voltage, is suitable for LED driver applications in smart homes. We propose simplified and minimal gate driving schemes for N level Dickson switched-capacitor scheme where the number of gate driver chips is limited to only 3 that leads to a substantial decrease of circuit board size and cost. Detailed loss analysis, considering soft charging effect from the output inductor, is presented. To examine the effectiveness of the proposed scheme, a GaN-based hybrid DC-DC converter prototype is implemented and experimentally verified using commercial LED lamps. The circuit offers a peak efficiency of over 94% and a peak current of ∼1A at an output range from 4 V to 28 V from a 40 V input for the simplified gate driving scheme. The converter prototype using the minimal gate driving scheme achieves a peak efficiency of ∼93% with ∼43% reduction in gate driver chips and ∼35% reduction in gate driver area, promising a compact and low-cost solution for future LED drivers.

Implementation of sliding mode backstepping controller for boost converter in real‐time for LED application

AbstractThis paper describes the real‐time implementation of a sliding mode backstepping controller for boost converters for LED lighting applications. The sliding surface is used to calculate the first error value in the backstepping control procedure, which ensures the system's robustness over a wide range of disturbances by achieving an asymptotically stable system based on the Lyapunov function. Due to the non‐minimum phase nature of boost converter, the system will become unstable. Hence the output voltage is indirectly controlled by controlling the sliding surface in the proposed sliding mode backstepping controller in order to achieve the asymptotically stable system. The detailed simulation is carried out on the MATLAB/Simulink platform, and the results are compared to that of a conventional proportional‐integral‐derivative (PID) controller and a traditional sliding mode controller, which ensures system robustness across a wide range of load resistance and input voltage changes, resulting in enhanced transient and, steady‐state responses. In the laboratory, a prototype of proposed controller is designed to ensure its accuracy in real‐time. By comparing the proposed control technique to the conventional sliding mode controller and PID controller, the flexibility of the proposed control method is validated for any variation at the input and output sides. From the experimental results, it is apparent that the proposed controller responds accurately and rapidly regardless of the disturbances caused to the system.

TECHNOLOGICAL METHODS FOR CORIANDER CULTIVATION ON VERTICAL RACKS

The research is aimed at specifying the possibility of cultivation and gain of marketable coriander products with minimum energy consumption in photoculture conditions. Growth of vegetative part, root system, the quality and photosynthetic activity of coriander (Coriandrum sativum L.) were evaluated with application of LED lighting in different spectral ratios. Coriander varieties were grown hydroponically on vertical racks using flooding technology. Illumination lamps based on blue, green and red LEDs were used as lighting, with a total PAR intensity of 150 mmol/m²s. Far red 6-12% was added to the main spectrum of illumination. The results showed that application of LED light (mainly red and green, and to a lesser extent blue light) significantly influenced a wide range of parameters of plant growth and development, including photosynthetic activity of pigments, the biomass of shoots and roots. The photosynthetic ability of the leaves was significantly higher under the radiation in the second variant with the addition of far red spectrum of 6% compared to other illumination variants. The root system parameters in different variants of the experiment differed slightly. The most appropriate ratio of LED emission spectra are B(23) :G(53):R(74) mmol/m²s with a far red spectrum share of 12% (option 1) for 'Santo' variety and B(21):G(59) :R(70) mmol/m²s with 6% far red (option 2) for 'Caribe' variety. The conditions of light culture ensure formation of economically useful biomass of coriander plants in a short period of 22-25 days, on average, in the amount of 1.81 kg/m². Studies showed that in case of growing coriander varieties on vertical hydroponics racks, it is possible to obtain high-quality green marketable products in the early stages at threshold values of photosynthetic irradiance.

Functional optical design of thickness-optimized transparent conductive dielectric-metal-dielectric plasmonic structure

Dielectric/metal/dielectric plasmonic transparent structures play an important role in tailoring the high-optical performance of various optoelectronic devices. Though these structures are in significant demand in applications, including modification of the optical properties, average visible transmittance (AVT) and colour render index (CRI) and correlated colour temperature (CCT), obtaining optimal ones require precise thickness optimization. The overall objective of this study is the estimation of the optimal design concept of MoO3/Ag/WO3 (10/dAg/dWO3 nm) plasmonic structure. To explore the proper use in optoelectronic devices, we are motivated to conduct a rigorous optical evaluation on the thickness of layers. Having calculated optical characteristics and achieved the highest AVT of 97.3% for dAg = 4 nm and dWO3 = 6 nm by the transfer matrix method, it is quite possible to offer the potential of the structure acting as a transparent contact. Notably, the colour coordinates of the structure are x = 0.3110 and y = 0.3271, namely, it attributes very close to the Planckian locus. This superior colour performance displays that MoO3/Ag/WO3 shall undergo rapid development in neutral-colour windows and LED technologies. Structure with dAg = 6 nm and dWO3 = 16 nm exhibits the highest CRI of 98.58, thus identifying an optimal structure that can be integrated into LED lighting applications and imaging technologies. Besides the colour of structure with dAg = 4 nm and dWO3 = 8 nm is equal for D65 Standard Illuminant, the study reports that the range of CCTs are between 5000 and 6500 K. This optimization makes the structure employable as a near-daylight broadband illuminant. The study emphasizes that optimal MoO3/Ag/WO3 plasmonic structures can be used effectively to boost optoelectronic devices' performance.

K replaces Rb towards cyan to red ultra-wideband perovskite-type phosphors for full-spectrum lighting

Near-ultraviolet-excited high-performance broad-emission phosphors are still an important challenge in full-spectrum LED lighting. According to the perovskite structure Rb2CaPO4F and K2CaPO4F, the broadband phosphor Rb2-wKwCaPO4F: Eu2+ (w = 0–2) suitable for near-ultraviolet excitation was studied, especially the phosphors with w of 0.5, 1 and 1.5. These three phosphors emit green, yellow and red light under excitation at 395 nm, and the full width at half maximum (FWHM) is 144 nm, 182 nm, and 174 nm, respectively, which is wider than the FWHM of commercial phosphors. Through the calculation of the formation energy and the change of the average bond length after Eu2+ doping, it can be determined that Eu2+ mainly occupies Ca2+ site. As K replaces Rb to change the coordination environment of Eu2+, the emission wavelength is continuously red-shifted and the FWHM is also changed. The series of phosphors Rb2-wKwCaPO4F: Eu2+ (w = 0–2) have high quantum efficiency and excellent thermal stability (more than 80%@150 °C of the integrated emission intensity at room temperature). The white LED synthesized by using the series of phosphors have a high color rendering index (Ra is greater than 90), a wide spectral range and a suitable correlated color temperature. These results indicate that Rb2-wKwCaPO4F: Eu2+ (w = 0–2) phosphors have great potential in full-spectrum LED lighting applications. This research also verifies that the photoluminescence adjustment strategy through cation substitution is the key to achieve tunable emission.

DCM Boost PFC for High Brightness LED Driver Applications

This paper is concerned with the derivation of a discontinuous conduction mode boost PFC rectifier as a driver for high-power LED lighting applications. The proposed driver is operated in the current mode regime while emulating a resistance towards the line, thus attaining a near unity power factor and low total harmonic distortion of the line current. Theoretical analysis is reported and conditions for the low LED flicker are derived. A method of design for minimum THD is also suggested. Simulation and experimental results are reported.

Luminescence enhancement of La4Ti9O24:Eu3+ red-emitting phosphors via cation-substitution of M (Ga, Nb, Ta, Zr, Al) ions

Eu3+- and M (Ga3+, Nb5+, Ta5+, Zr3+, Al3+)-co-doped La4Ti9O24 phosphors were prepared by the solid-state reaction method. The structural phase formation, luminescence properties, and possible LED-lighting application were investigated. The undoped La4Ti9O24 shows an indirect transition with a band-energy of 2.88 ​eV La4Ti9O24 has a broad intrinsic emission band (350–700 ​nm) peaked at 530 ​nm (2.34 ​eV) at 300K. Eu3+-doped La4Ti9O24 presents red luminescence from 5D0→7FJ (J ​= ​0, 1, 2, 3, 4) transitions, which was obviously enhanced with the cation-substitution of M (Ga3+, Nb5+, Ta5+, Zr3+, Al3+) on Ti4+ sites in the lattices. The typical thermal quenching of La3.72Eu0.28Ti8.55M0.45O24 (M ​= ​Al) phosphor is ΔE ​= ​0.342 ​eV. Importantly, the optical excitation of the samples fit well with the commercial LED-chip because of its efficient absorption in near-UV region (395 ​nm) and blue (465 ​nm) wavelength region. The red-LED device packaging with the optimal phosphor was achieved, which has a luminous efficiency of 42 lm/W with a working current of 200 ​mA and a testing voltage of 3.2 ​V. The experiments suggest that the phosphor could be potential for solid-state LED-lighting and display.

Assessment of Outdoor Lighting: Methods for Capturing the Pedestrian Experience in the Field

This study assessed whether methods for capturing the pedestrian experience of outdoor lighting, previously evaluated in a full-scale laboratory, were applicable in a real-world setting. It applied an approach capturing the human response to outdoor lighting in a systematic way, by assessing perception, evaluation and behaviour in the lit environment. The study involved 81 participants from two age groups (Young—n: 48, mean age: 26, 63% women; Elderly—n: 33, mean age: 69, 67% women) and was carried out on a pedestrian path in a park in the centre of Malmö, Sweden, in the evenings during wintertime. Two LED lighting applications, differing in light distribution, uniformity and horizontal illuminance, were presented, and the pedestrians’ perception (facial expression recognition and sign reading), evaluation (arousal, valence and perceived outdoor lighting quality) and behaviour (pedestrian flow) were assessed. The results from the perceptual tasks differed significantly between the lighting applications, in favour of the lighting application with greatest uniformity and horizontal illuminance. There was a significant difference in sign reading distance between the two age groups. The methods applied in this study are feasible to administer and could be used to assess lighting solutions in order to capture the needs of vulnerable groups.

Effect of digestate loading rates on microalgae-based treatment under low LED light intensity

ABSTRACT Low red-LED irradiances are an attractive alternative for enhancing microalgae photobioreactors treating digestate due to their potential contribution in decreasing area footprints with low energy consumptions. However, more information is required regarding the influence of digestate load on treatment performance and biomass valorisation when low-intensity red-LEDs are applied. Thus, this study assessed microalgae-based photobioreactors treating food waste digestate under different concentrations (5%, 25%, 50%, and 75%, v/v) at low red-LED irradiance (15 µmol·m−2·s−1). The removal efficiencies of soluble chemical oxygen demand (sCOD) at the end of the experiment ranged from 45% to 75% when treating influent loads between 5.3 and 79.1 g sCOD·m−3·d−1 (5% and 75%-digestate), respectively. Total ammonia nitrogen (TAN) was applied in loading rates between 3.2 and 48.5 g TAN·m−3·d−1 (5% and 75%, respectively) and removed with maximum efficiencies of 90%–100% in all trials. Nitrification-denitrification was proportionally more relevant when treating 5%-digestate, whereas volatilisation was the primary process in 25%, 50% and 75% concentrations. Microalgae presented adequate yields in all treatments, except in 75%-digestate, likely due to the blocking of light by the high solids concentrations. The assessment of the microalgae community and chlorophyll-a and carotenoids suggested that chlorophytes, mainly Dictyosphaerium pulchellum and Scenedesmus sp. grew autotrophically, whereas cyanobacteria Pseudanabaena sp. grew mixotrophically. Moreover, the sustainability of red LED lighting applications can be increased by anaerobic digestion or agricultural valorisation of the biomass, enabled by its high N and P contents. Low-intensity red-LEDs may have promissory applications in the treatment of high-strength wastewaters.

Generating-function approach for double freeform lens design.

Many LED lighting applications involve the design of multiple optical surfaces. A prime example is a single lens with two refractive surfaces. In this paper, we consider an LED light source approximated as a point and a far-field target intensity. Using Hamilton's characteristic functions, the design problem is converted into two generalized Monge-Ampère equations by deriving a generating function for each optical surface. The generating function is a generalization of the cost function in optimal transport theory. The generalized Monge-Ampère equations are solved using an iterative least-squares algorithm. To compute the first optical surface, we choose an intermediate far-field target intensity. By choosing different intermediate target intensities based on the source and target intensity, we develop a "knob" to distribute the refractive power over both surfaces of the lens. We apply the algorithm on two example problems and show it is capable of producing complicated target distributions.

Research and application of LED lighting in the healing stage of grafted vegetable seedlings

Research and application of LED lighting in the healing stage of grafted vegetable seedlings

Alkylamine screening and zinc doping of highly luminescent 2D tin-halide perovskites for LED lighting

Highly luminescent and stable two-dimensional tin-halide perovskites for LED lighting applications were achieved through alkylamine screening and zinc doping.

The state of art in the horticulture lighting

The article presents an overview of currently used greenhouse lighting systems. It does not apply to traditional sodium lighting systems, but only to the most modern LEDs. The publication presents descriptions of lamp designs, both foreign and Polish. The aim of the work is not only to review solutions, but also to identify the reasons for the low transfer of scientific and technical solutions to business. There are several barriers to overcome, mainly subjective ones, so that new solutions can be implemented and developed. Full Text: PDF ReferencesS. Ki-Ho, J. Yu-Min, O. Myung-Min, "Application of supplementary white and pulsed light-emitting diodes to lettuce grown in a plant factory with artificial lighting", Springer 57(6), 561 (2016). CrossRef M. Gilewski, "The role of light in the plants world", Phot. Lett. Poland 11, 4 (2019). CrossRef K.J. McCree, Agricultural Meteorology (Elsevier Publishing Company 1972). CrossRef G. Trouwborst, J. Oosterkamp, S. Hogewoning, V. Ieperen, "The application of LEDs as assimilation light source in greenhouse horticulture: A simulation study", the 6th Int. Symposium on Light in Horticulture. Tsukuba. Japan, Nov. 2009. CrossRef K. Jaworski, A. Szmidt-Jaworska, J. Kopcewicz, " Two calcium dependent protein kinases are differently regulated by light and have different activity patterns during seedling growth in Pharbitis nil", Springerlink.com, Journal: 10725, Article: 9609, 2011. CrossRef Philips Lighting, Horticultural LED lighting applications, 2020: https://www.lighting.philips.com/main/products/horticulture. DirectLink E. de Beer, P.H. van Baar, 3 reasons why intercanopy lighting is effective for high-wire vegetables, 2020: www.lighting.philips.com. DirectLink HLG, Refurbished HLG 550, 2020, https://horticulture-lightinggroup.com/collections/lamps/products/refurbished-hlg-550-v1 DirectLink Neonica Polska, 2020, www.growy.eu CrossRef I. Fryc, T. Dimitrova-Grekow, "An automated system for evaluation of the quality of light sources", 6th IEEE Lighting Conference of the Visegrad Countries : LUMEN V4, Sept. 2016. CrossRef EconoLux Ind. Ltd., "What Light do Plants Need", Hong Kong, 2016, http://econoluxindustries.com/light-plants-need.html. DirectLink Heliospectra AB, heliospectra DYNA, 2020, https://www.heliospectra.com/led-grow-lights/dyna. DirectLink Plantlux, Horticulture LED SMD lamp Plantalux XX640W, 2020, https://plantalux.pl/en/plantalux-xx640w-en/. DirectLink M. Gilewski, "An Adaptive and Monoculture Oriented LEDs Lamp", 978-1-5386-7924-1/18/$31.00 ©2018 IEEE, 2018. CrossRef

Design and Evaluation of Uniform LED Illumination Based on Double Linear Fresnel Lenses

Redistribution of LED radiation in lighting is necessary in many applications. In this article, we propose a new optical component design for LED lighting to achieve a higher performance. The design consists of a commercial collimator and two linear Fresnel lenses. The LED radiation is collimated by a collimator and redistributed by double linear Fresnel lenses to create a square-shaped, uniform distribution. The linear Fresnel lenses design is based on Snell’s law and the “edge-ray principle”. The optical devices are made from poly methyl methacrylate (PMMA) using a high-speed computer numerical control (CNC) machine. The LED prototypes with complementary optics were measured, and the optical intensity distribution was evaluated. The numerical results showed we obtained a free-form lens that produced an illumination uniformity of 78% with an efficiency of 77%. We used the developed LED light sources for field experiments in agricultural lighting. The figures of these tests showed positive effects with control flowering criteria and advantages of harvested products in comparison with the conventional LED sources. This allows our approach in this paper to be considered as an alternative candidate for highly efficient and energy-saving LED lighting applications.