Research

9 pages, 1697 KiB

Open AccessArticle

Blue-Light Levels Emitted from Portable Electronic Devices Compared to Sunlight

by David Baeza Moyano, Yolanda Sola and Roberto Alonso González-Lezcano

Energies 2020, 13(16), 4276; https://doi.org/10.3390/en13164276 - 18 Aug 2020

Cited by 19 | Viewed by 5622

Over recent years, a technological revolution has taken place in which conventional lighting has been replaced by light emitting diodes (LEDs). Some studies have shown the possibility that blue light from these artificial sources could have deleterious effects on the retina. Considering that [...] Read more.

Over recent years, a technological revolution has taken place in which conventional lighting has been replaced by light emitting diodes (LEDs). Some studies have shown the possibility that blue light from these artificial sources could have deleterious effects on the retina. Considering that people spend a non-negligible time in front of screens from computers and mobile phones, the eyes receive blue light of different intensities depending on the source. Nevertheless, any study about the visual and non-visual effects of blue light must consider precise measurements taken from actual artificial sources. For this reason, we have analyzed the spectral emission of 10 different electronic devices and weighted them according to the hazard caused by blue light to the eyes, comparing the results with solar radiation simulated with a radiative transfer model. The maximum spectral irradiance of the measured electronic devices at 10 cm from the detector was located between 440 nm and 460 nm. The irradiance for blue light hazard ranged from 0.008 to 0.230 Wm⁻² depending on the particular characteristics of each electronic device. In contrast, the solar radiances in the same spectral range are larger both under clear and cloudy conditions. Full article

(This article belongs to the Special Issue Technology Evolution and Power Quality Issues in Designing Future Lighting Systems)

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18 pages, 5672 KiB

Open AccessArticle

AC–DC Flyback Dimmable LED Driver with Low-Frequency Current Ripple Reduced and Power Dissipation in BJT Linearly Proportional to LED Current

by Yeu-Torng Yau, Kuo-Ing Hwu and Kun-Jie Liu

Energies 2020, 13(16), 4270; https://doi.org/10.3390/en13164270 - 18 Aug 2020

Cited by 5 | Viewed by 2979

Abstract

In this paper, a dimmable light-emitting diode (LED) driver, along with the low-frequency current ripple decreased and the bipolar junction transistor (BJT) power dissipation reduced, is developed. This driver is designed based on a single-stage flyback converter. On the one hand, the low-frequency [...] Read more.

In this paper, a dimmable light-emitting diode (LED) driver, along with the low-frequency current ripple decreased and the bipolar junction transistor (BJT) power dissipation reduced, is developed. This driver is designed based on a single-stage flyback converter. On the one hand, the low-frequency output current ripple reduction is based on the physical behavior of the linear current regulator. On the other hand, when the voltage across the LED string is decreased/increased due to dimming or temperature, the output voltage of the flyback converter will be automatically regulated down/up, thereby making the power dissipation in the BJT linearly proportional to the LED current. By doing so, not only the power loss in the linear current regulator will be decreased as the LED current is decreased or the LED temperature rises, but also the output current ripple can be reduced. Furthermore, the corresponding power factor (PF) is almost not changed, and the total harmonic distortion (THD) is improved slightly. In addition, the LED dimming is based on voltage division. Eventually, a 30 W LED driver, with an input voltage range from 85 to 295 V_rms and with 24 LEDs in series used as a load, is developed, and accordingly, the feasibility of the proposed LED driver is validated by experimental results. Full article

(This article belongs to the Special Issue Technology Evolution and Power Quality Issues in Designing Future Lighting Systems)

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22 pages, 7492 KiB

Open AccessArticle

Modeling of Selected Lighting Parameters of LED Panel

by Krzysztof Baran, Antoni Różowicz, Henryk Wachta and Sebastian Różowicz

Energies 2020, 13(14), 3583; https://doi.org/10.3390/en13143583 - 11 Jul 2020

Cited by 17 | Viewed by 2410

Abstract

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 [...] Read more.

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. Full article

(This article belongs to the Special Issue Technology Evolution and Power Quality Issues in Designing Future Lighting Systems)

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24 pages, 5188 KiB

Open AccessArticle

Analysis of the Input Current Distortion and Guidelines for Designing High Power Factor Quasi-Resonant Flyback LED Drivers

by Claudio Adragna, Giovanni Gritti, Angelo Raciti, Santi Agatino Rizzo and Giovanni Susinni

Energies 2020, 13(11), 2989; https://doi.org/10.3390/en13112989 - 10 Jun 2020

Cited by 7 | Viewed by 3006

Abstract

Nowadays, LED lamps have become a widespread solution in different lighting systems due to their high brightness, efficiency, long lifespan, high reliability and environmental friendliness. The choice of a proper LED driver circuit plays an important role, especially in terms of power quality. [...] Read more.

Nowadays, LED lamps have become a widespread solution in different lighting systems due to their high brightness, efficiency, long lifespan, high reliability and environmental friendliness. The choice of a proper LED driver circuit plays an important role, especially in terms of power quality. In fact, the driver controls its own input current in addition to the LED output current, thus it must guarantee a high power factor. Among the various LED drivers available on the market, the quasi-resonant (QR) flyback topology shows interesting benefits. This paper aims at investigating and analyzing the different issues related to the input current distortion in a QR flyback LED driver. Several effects, such as the distortion caused by the ringing current, crossover distortion due to transformer leakage inductance and crossover distortion due to the input storage capacitor have been experimentally reported. These effects, not previously studied for a high power factor (Hi-PF) QR flyback, have been analyzed in depth. Finally, some practical design guidelines for a Hi-PF QR flyback driver for LED applications are provided. Full article

(This article belongs to the Special Issue Technology Evolution and Power Quality Issues in Designing Future Lighting Systems)

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16 pages, 7494 KiB

Open AccessArticle

Three-Legs Interleaved Boost Power Factor Corrector for High-Power LED Lighting Application

by Salvatore Musumeci, Radu Bojoi, Eric Armando, Stefano Borlo and Fabio Mandrile

Energies 2020, 13(7), 1728; https://doi.org/10.3390/en13071728 - 04 Apr 2020

Cited by 13 | Viewed by 2878

Abstract

In this article, a three-leg interleaved boost Power Factor Corrector (IBPFC) converter for energy-efficient LED lighting systems connected to the main grid was discussed. This IBPFC circuit presented features 60 kHz of commutation frequency and up to 3 kW of power rating. The [...] Read more.

In this article, a three-leg interleaved boost Power Factor Corrector (IBPFC) converter for energy-efficient LED lighting systems connected to the main grid was discussed. This IBPFC circuit presented features 60 kHz of commutation frequency and up to 3 kW of power rating. The controlled rectifier front-end boost PFC supplied a DC/DC converter to drive power LEDs suitable for street lighting or a lighting system for a stadium, etc. The IBPFC operated in continuous current mode (CCM). The ripple impact of the IBPFC converter was analyzed and a novel methodology of inductance design was presented. In the proposed design approach, the derivative calculation of the current ripple peak compared with the derivative of the input current was used to define a critical inductance value to ensure the CCM condition. Experimental validation was provided on a 3kW prototype. Full article

(This article belongs to the Special Issue Technology Evolution and Power Quality Issues in Designing Future Lighting Systems)

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33 pages, 3311 KiB

Open AccessArticle

Analysis of Approaches for Modeling the Low Frequency Emission of LED Lamps

by Adam J. Collin, Sasa Z. Djokic, Jiri Drapela, Zekun Guo, Roberto Langella, Alfredo Testa and Neville R. Watson

Energies 2020, 13(7), 1571; https://doi.org/10.3390/en13071571 - 31 Mar 2020

Cited by 19 | Viewed by 2710

Abstract

Light emitting diode (LED) lamps are now an established lighting technology, which is becoming prevalent in all load sectors. However, LED lamps are non-linear electrical loads, and their impact on distribution system voltage quality must be evaluated. This paper provides a detailed analysis [...] Read more.

Light emitting diode (LED) lamps are now an established lighting technology, which is becoming prevalent in all load sectors. However, LED lamps are non-linear electrical loads, and their impact on distribution system voltage quality must be evaluated. This paper provides a detailed analysis of time domain and frequency domain approaches for developing and evaluating models suitable for use in large scale steady-state harmonic power flow analysis of the low frequency (LF) emission of LED lamps. The considered approaches are illustrated using four general categories of LED lamps, which have been shown to cover the vast majority of LED lamps currently available on the market. The aim is an in-depth assessment of the ability of commonly applied models to represent the specific design characteristics of different categories of LED lamps. The accuracy of the models is quantitatively evaluated by means of laboratory tests, numerical simulations, and statistical analyses. This provides an example, for each LED lamp category, of comprehensive information about the overall accuracy that can be achieved in the general framework of large scale LF harmonic penetration studies, particularly in the assessment of voltage quality in low voltage networks and their future evolution. Full article

(This article belongs to the Special Issue Technology Evolution and Power Quality Issues in Designing Future Lighting Systems)

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22 pages, 13367 KiB

Open AccessArticle

Adaptive Luminaire with Variable Luminous Intensity Distribution

by Marcin Leśko, Antoni Różowicz, Henryk Wachta and Sebastian Różowicz

Energies 2020, 13(3), 721; https://doi.org/10.3390/en13030721 - 07 Feb 2020

Cited by 15 | Viewed by 2869

Abstract

The field of indoor lighting covers a wide range of lighting uses with varying requirements for lighting conditions to be satisfied by properly selected lighting equipment. The need to frequently change the arrangement of useable areas entails the necessity to adapt the lighting [...] Read more.

The field of indoor lighting covers a wide range of lighting uses with varying requirements for lighting conditions to be satisfied by properly selected lighting equipment. The need to frequently change the arrangement of useable areas entails the necessity to adapt the lighting to new requirements. A good solution for reducing costs and saving time is a luminaire adjusting the luminous flux and spatial luminous intensity distribution in a wide range. The authors present the concept of an adaptive luminaire and its construction assumptions. In addition, the results of studies on the development of the concept are shown together with conditions and limitations that influenced the construction of the luminaire. The analysis of the surface of the moveable reflector is presented, and the results of testing the luminaire prototype are compared with the results of simulation tests. Full article

(This article belongs to the Special Issue Technology Evolution and Power Quality Issues in Designing Future Lighting Systems)

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20 pages, 9898 KiB

Open AccessArticle

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

by Krzysztof Baran, Antoni Różowicz, Henryk Wachta, Sebastian Różowicz and Damian Mazur

Energies 2019, 12(20), 3941; https://doi.org/10.3390/en12203941 - 17 Oct 2019

Cited by 19 | Viewed by 3178

Abstract

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 [...] Read more.

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. Full article

(This article belongs to the Special Issue Technology Evolution and Power Quality Issues in Designing Future Lighting Systems)

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12 pages, 5469 KiB

Open AccessArticle

Hollow Light Guide Module Involving Mini Light-Emitting Diodes for Asymmetric Luminous Planar Illuminators

by Zhi Ting Ye, Chin Lung Chen, Lung-Chien Chen, Ching Ho Tien, Hong Thai Nguyen and Hsiang-Chen Wang

Energies 2019, 12(14), 2755; https://doi.org/10.3390/en12142755 - 18 Jul 2019

Cited by 12 | Viewed by 3109

Abstract

Light-emitting diodes (LEDs) have numerous advantages. However, LEDs only offer a point light source. Therefore, transforming LEDs into planar light sources is a new objective in general lighting applications. Solid light guides have strong uniformity but are marred by their material absorption characteristics [...] Read more.

Light-emitting diodes (LEDs) have numerous advantages. However, LEDs only offer a point light source. Therefore, transforming LEDs into planar light sources is a new objective in general lighting applications. Solid light guides have strong uniformity but are marred by their material absorption characteristics and weight. Hollow light guides constitute a solution to the weight problem but exhibit poor uniformity and necessitate sacrificing efficiency to enhance uniformity. To resolve the uniformity, weight, and efficiency problems simultaneously, we propose a hollow light guide architecture involving mini-LEDs with asymmetric luminous intensity. To develop this guide module, we first optimized the aspect ratio of the cavity and then modulated the light path by using varied angles of the reflection surface on the end wall of the module. We then designed a beveled reflection surface near the mini-LEDs to further enhance uniformity. An archetype of the proposed architecture for planar light source modules had a width and depth of 51.5 and 9.95 mm, respectively. Experimental results revealed a total efficiency of 83.9% and uniformity of 92.3%. The module weight was determined to be 215 g, which was 40% lighter than that of similarly sized solid light guide modules. Full article

(This article belongs to the Special Issue Technology Evolution and Power Quality Issues in Designing Future Lighting Systems)

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12 pages, 1951 KiB

Open AccessArticle

Laser Headlamp with a Tunable Light Field

by Kuang-Wen Tseng, Ting-Hao Chen, Shiu-Jau Chen, Yuan-De Su, Hsiang-Chen Wang, Shih-Wei Feng, Zhi Ting Ye and Kuo-Hsien Tu

Energies 2019, 12(4), 707; https://doi.org/10.3390/en12040707 - 21 Feb 2019

Cited by 10 | Viewed by 3280

Abstract

This study developed an optical module for laser headlamps with a tunable light field. Laser headlamps have high and low beam lighting functions that are applied by changing the numbers of unit headlamps. For regulatory validation, we validated the project in accordance with [...] Read more.

This study developed an optical module for laser headlamps with a tunable light field. Laser headlamps have high and low beam lighting functions that are applied by changing the numbers of unit headlamps. For regulatory validation, we validated the project in accordance with the Regulation No. 112 of the Economic Commission for Europe (ECE) to determine whether the results meet the regulatory requirements or not. The proposed design increased the lighting distance by 2.14 times and decreased the size of the mechanism by 45% relative to the values for LED headlamps. High and low beam lighting functions were provided by the same laser sources. Full article

(This article belongs to the Special Issue Technology Evolution and Power Quality Issues in Designing Future Lighting Systems)

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