Controls for Solid-State Lighting

Adoption of LED lighting in large scale has opened a debate on how to evaluate performance of commercially available LED lighting products. In this paper a review of existing photometric flicker metrics and measurement methods for LED lighting products is discussed. There is an urgent need to characterize potentially visible temporal light artifacts, or popularly known as flicker from light sources. Conventional light sources like incandescent and discharge lamps modulate light output, but the severity and diversity of light modulation exhibited by LED lighting products has generated curiosity in quantifying and understanding flicker and its impact on human health and productivity. Flicker metrics like flicker index and percentage flicker are not made available in datasheets of LED lighting products. It is critical for lighting designer to obtain this important information from LED luminaire manufacturers or conduct independent testing of LED luminaires to measure flicker metrics. The data reported in this paper show great inconsistency in flicker profile waveforms (flicker profiles) of some typically commercially available LED lighting products. Flicker is hence an important characteristic that the lighting designer needs to consider in assessing LED products. This paper presents a traditional method to develop a minimum suggested performance criteria for flicker measurement and reporting, understanding the performance needs of known lighting applications and including results from significant researchers in the field. It is important to minimize the chance of mismatching LED lighting products is installed in areas where flicker can be very serious health hazard or where it can hamper productivity and human comfort.

Libya is one of the countries blessed with high potential of renewable energy. Currently, the electricity in Libya is produced from fossil fuel to meet the demand on the local electricity market. In the near future, the demand on the energy will increase significantly. The growth in energy demand will lead to more oil and gas consumption in Libya. Additionally, the CO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> emissions will increase substantially. Therefore, Libya should make an urgent plan to use its alternative energy supplies to cover some of its load requirements. For example street lighting forms around 20% of the electricity consumption. The street lighting system in Libya is based on the high pressure sodium lamps which are powered from the electricity grid. The lamp rating ranges from 250 to 400 watts. As the country struggles to satisfy its electricity demands we propose replacing the conventional street lighting system with solar powered LED (Light emitting Diode) lighting system. The paper presents a case study for 4 km solar street lighting system in Almarj city. Two proposals are investigated, the conventional lighting system and the solar powered LED lighting system. A feasibility study of the street lighting system is carried out. The cost, energy savings and the CO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> emission of the two proposed systems are compared. The cost of the solar powered LED street lighting system is 1,250,200 LD, while the cost of the high pressure Sodium lamp street lighting system is 2,117,255 LD. Additionally, the solar powered LED street lighting system has no CO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> emissions.

Visual comfort is a subjective aspect related to road-lighting quality. If the degree of visual comfort is not good enough, a motorist’s level of fatigue will increase and as a consequence, his visual performance and alertness will decrease. So both visual comfort and visual performance are important for road safety. Subjective appraisal studies have shown that the lighting level, the uniformity of the roadsurface luminance pattern and glare have an influence on visual comfort. The same type of studies have been the basis for definitions of visual comfort metrics such as longitudinal uniformity, luminance gradient and discomfort glare marks. The spectrum of the light source used has an influence on the last mentioned. LEDs may sometimes have a special influence on visual comfort because they are available in a much wider range of spectra than are the conventional light sources. Their small light-emitting surfaces enable more pronounced beams to be produced, that in turn may influence visual comfort or discomfort. Most LED luminaires consist of a multiple array of small LEDs resulting in a non-uniform luminance distribution of the light-emitting surface, which may have an influence on their discomfort glare aspect.

Nowadays the three-dimensional printer has widely use in the various application including art, fashion, sculpture, and even for medical purpose. The common technique that used in the three-dimensional printer is the Stereolithography (SLA) process based on liquid resin material. This study develops a LCD-based technique to overcome the high price of the digital light processing (DLP) and digital mirror device (DMD). Experimental results show that the developed system has lower efficiency than that of the DLP method which caused by the longer exposure time. The aim of this study is also to propose a new method in the LCD based three-dimensional printer to gain its efficiency in the printing process particularly in the curing time using LED array as the lighting sources. The experiment result shows the exposure time using LED array as the lighting source in the LCD-based three-dimensional printer can reduce the exposure time being around 25-30 seconds for each layer. It means by using LED array as a lighting system in the LCD-based-three dimensional printer can increase the efficiency of the printing process around 78% instead of the using conventional light system or single light source.

The paper is to develop highly reliable LED luminaires for high-temperature applications, which are often needed in hush or hazardous industrial environments. An improved MIL-HDBK-217F method is introduced to study the reliability and predict the lifetime of different LED driving technologies, and confirmed by accelerated life testing results in order to optimize the design towards high reliability and long lifetime. Based on the analysis results of a AC-direct driving LED driver and a switched-mode LED driver, the paper demonstrates that the AC-direct driving technology is a better driving solution for LED luminaires used in high-temperature environments due to its capability to operate at higher temperatures and longer lifetime at the same temperature compared to the traditional switched-mode driving technology. Also, the paper has some discussions on optimizing the design of the AC-direct driving circuits for long lifetime in high temperature applications. As a result, a 4000+ lumen AC-direct driving LED luminaire is developed, which has achieved 2-3 times longer lifetime at 65 °C ambient and can operate safely up to 80 °C ambient (15 °C higher) compared to its switched-mode counterpart.

Numerous efforts have been made to investigate how light source color rendition affects color preference. Though the effect of light level on color appearance (known as the Hunt effect) was found in 1952, most studies investigating color preference under light sources only employed a single illuminance level and the illuminance levels were typically between 200 and 1000 lux. This article reports two psychophysical experiments that were designed to investigate how light source color rendition affected color preference across a wide range of illuminance levels, from 20 to 15,000 lux. The observers compared the color appearance of an artwork under nine nearly metameric light stimuli with a correlated color temperature (CCT) of 3000 K at different illuminance levels. These light stimuli were carefully designed to have different abilities to enhance the chroma of red and green colors, so that they had different gamut areas R g (between 100 and 124 in Experiment 1 and between 99 and 117 in Experiment 2). It was found that the illuminance level significantly affected the observers’ judgments, with a light stimulus with a greater R g being preferred at a lower light level. The light stimuli with an R g beyond 100 were preferred at the light levels from 20 to 5000 lux, whereas those with an R g around 100 were preferred at very high light levels (i.e., 10,000 and 15,000 lux). This suggested that the preference to the stimuli with an R g beyond 100, as found in many past studies, was likely due to the relatively lower illuminance levels in comparison to the daylight illuminance levels. In addition, the calculations of the color attributes of the artwork under the preferred stimuli suggested that CIECAM02 may overestimate the effect of light level on color appearance, especially when the light level was very high, which merits further investigations.

Reliability evaluation for products with long lifetime and high reliability is a great challenge in reliability engineering. LED luminaires are one of the most popular lighting solutions of the current society due to their long-lasting and energy-efficient. The system reliability of the LED luminaire is determined by the performance of the driver electronics. This paper analyzes the LED driver failure forms and the possible causes, in order to study the failure mechanism of LED driver and predict the lifetime. The accelerated life model of the driver is also established and the method to get the parameters in the model has been discussed. A high accelerated life testing platform has been built to test the sample's lifetime and get the parameters in the accelerated life model. The lifetime of sample is estimated by the model quickly and correctly.

Since the first electrical integrated circuits (ICs), the level of integration has been increasing with the scaling down of transistors. Although it is possible to integrate a number of transistors in a single chip, however, the ICs suffers from a performance bottleneck. To eliminate the performance bottleneck, an on-chip optical interconnect system has been in the limelight. However, developments in on-chip interconnect system have been made slow progress due to the absence of efficient on-chip light sources. Germanium (Ge) is the promising material for the on-chip optical interconnect system. However, Ge is not suitable for light sources because of its poor light emission efficiency. Thus, an efficient light source is the only missing key for the on-chip optical interconnect system. Throughout this thesis, we discuss our achievements about the efficient Ge based light sources, which can pave the way towards the on-chip optical interconnect system.

Easily controlled LED luminaires with a wide range of light colours and intensities have been developed recently. Their characteristics can be adjusted to mimic that of natural daylight. However, considering that the colour and intensity of daylight vary constantly with time and weather, it is necessary to verify whether the same effect can be achieved using LED luminaires for interior lighting. Therefore, this study examined a method for reproducing the correlated colour temperature (CCT) and illuminance fluctuations of daylight using LED luminaires. Two experiments were conducted using daylight or LED luminaires as the light source, and the physiological and psychological effects on the participants were compared in both experiments to verify whether the same effect can be achieved. The results showed no significant differences between daylight and LED luminaires in terms of physiological and psychological effects.

With the increasing global emphasis on energy conservation and emission reduction, LED luminaires have become a hot topic in the field of lighting due to their high efficiency and energy-saving characteristics. This paper aims to explore the design and optimization of high-efficiency and energy-saving LED luminaires to improve their luminous efficacy, heat dissipation performance, and energy efficiency. First, the optical characteristics of LED luminaires, including the principles of light emission, light intensity distribution, and beam angle, are analyzed, and the basic principles and common methods of optical design are introduced. Then, through the use of optical simulation software, the light distribution is optimized, and optimization strategies for light distribution in different application scenarios are proposed. In terms of thermal management, the selection and layout of heat sinks are studied, and the advantages and disadvantages of heat sinks made of different materials are analyzed. The thermal performance is verified through experiments and numerical simulations. In addition, the design of high-efficiency driver circuits, including constant current driving and dimming functions, is explored to enhance the energy efficiency of the luminaires. Finally, through case studies of practical applications, the importance of integrated design of optics, thermodynamics, and circuits is demonstrated, and suggestions for further optimization of luminaire design are put forward. The research results show that by comprehensively optimizing the optical design, thermal management, and driver circuits, the performance of LED luminaires can be significantly improved, contributing to energy conservation and emission reduction.

LED조명장치는 자동차분야, 항공, 디스플레이, 전송장치 그리고 특수조명등의 응용장치로의 활용이 증가하고 있다. 일반적으로 고출력 RGB 멀티칩 LED는 표시용이나 경관조명용 또는 감성조명용으로 적용되고 백색 LED는 표시용 조명에서 최근 들어 일반조명용으로 적용되고 있으며, 고출력 백색 LED의 출시와 광효율의 증가는 이를 더욱 가속화하고 있다.BR 본 논문에서는 백색 LED와 RGB 멀티칩 LED 조명장치를 동일한 사양으로 제작하여 물리적, 전기적, 광학적 조명특성을 분석하여 향후 LED조명시스템의 제작에 정량적 데이터를 제공하고자 한다. 이를 위해 LED의 주요한 물리적 특성인 방열특성에 대한 성능분석, 전기적 특성의 분석을 위한 전력 및 드라이브 효율에 대한 성능분석을 수행하였고 조명특성을 위한 연색성, 배광특성, 광효율을 측정하였다. 백색 LED와 RGB 멀티칩 LED 조명장치를 활용한 응용장치의 적용방법을 확립하고 나아가 다양한 조명시스템에 LED 조명장치를 적용하는데 참고가 되는 기초 데이터를 제시하고자 한다.

New generation of standalone LED driver platforms developed, which are more efficient These LED Drivers are more efficient (≥90%), smaller in size ( 0.15 in3/watt), lower in cost ( 12 cents/watt in high volumes in millions of units). And these products are very reliable having an operating life of over 50,000 hours. This technology will enable growth of LED light sources in the use. This will also help in energy saving and reducing total life cycle cost of LED units. Two topologies selected for next generation of LED drivers: 1) Value engineered single stage Flyback topology. This is suitable for low powered LED drivers up to 50W power. 2) Two stage boost power factor correction (PFC) plus LLC half bridge platform for higher powers. This topology is suitable for 40W to 300W LED drivers. Three new product platforms were developed to cover a wide range of LED drivers: 1) 120V 40W LED driver, 2) Intellivolt 75W LED driver, & 3) Intellivolt 150W LED driver. These are standalone LED drivers for rugged outdoor lighting applications. Based on these platforms number of products are developed and successfully introduced in the market place meeting key performance, size and cost goals.

Lighting is an indispensable energy end use of man. A significant number people in developing countries live without electric lighting and depend on oil-based lamps. Globally, lighting consumes substantial amount of energy and is a major contributor to green house emissions. Conventional electric lighting systems such as incandescent lamps are highly inefficient and waste energy while the fluorescent/CFL lamps contain toxic chemicals like mercury. Incandescent lamps with short lifespan as well as the fluorescent/CFL lamps pose environmental waste disposal problems (e.g.). The use of renewable energy resource such as solar and wind power systems for example as sources of power for the most efficient and long life lighting source such as high-brightness light emitting diodes (LEDs) (also known as solid state lighting) would reduce global energy consumption for lighting by half, with corresponding reduction in green house emissions. In developing countries solar powered solid state lighting (SPSSL) would ensure access to electric lighting by the disperse population who may not be connected to the national grid in the near feature. In this article we elaborately review the upcoming solid state lighting technology. The physics and principles of operation of LEDs are also reviewed. The impact of this new lighting technology on developing countries in the areas of commerce, education, health and environmental impacts in comparison to conventional lighting technologies is the main thrust of this review.

Road luminaries are required to provide the luminance specified in the standards according to the road characteristics. For this reason, the light from the light source should be directed according to the desired conditions. While the range of minimum average road surface luminance recommended for different classes of road are provided; at the same time, it is desirable to be economical. In this study, a freeform lens and LED luminaire design with high luminous efficacy, low glare and uniform luminance distribution with a height of 1.5 m and a distance of 7 m between poles were designed for M3 road standards. First of all, lens design was made by using optical and illumination design software. Also, lens manufacturing and luminaire production were made as a result of the success of the design simulation test. The success of the LED luminaire in providing CIE standards has been measured on the designed road. In addition, the advantages and disadvantages have been determined by comparing with High Pressure Sodium Vapor (HPS) lamps.

This paper presents a discussion about the use of a low frequency boost pre-regulator as offline LED driver and its application to a street lighting LED luminaire. This simple and low cost converter may provide high power factor, low input current distortion, high efficiency and compliance with IEC 61.000-3-2 Class C standard, which limits the emission of harmonic currents of lighting equipment. The analysis of the boost pre-regulator is revised. Computational simulation and experimental results are shown to an LED luminaire operating in 155W. In this case, no transformers and electrolytic capacitors are required, which define higher converter efficiency and an extended lifetime for this driver.