The thesis gives an overview of the issue of control of full-color RGB LED panels with a large number of rows and columns. It deals with communication protocols for image transfer and information exchange. It focuses on implementing the FPGA into the RGB LED control structure. In the first half, the thesis focuses on deepening the theoretical knowledge about LED technologies, their control and color display. It further solves communication with superior elements. The last part of the theory is dedicated to FPGA circuits. The second part of the thesis describes the practical design of the FPGA circuit from UART and SPI communication through data storage from the communication to the panel control itself.

This thesis deals with automotive headlamps, focusing on layout of temparature field and its influence on thermal stress of used materials, describes their history, kinds and ongoing research. Thesis shortly describes light and its characteristics, heat and heat transfer and means of temperature measurement. Main part of the tesis is dedicated to measuring front headlamp serving as a fog light, concretely measuring temperature field and illuminance depending of ambient temperature. Thesis contains everything from the first preparations, creation of measuring circuit, programming of measuring to processing acquired data. Thesis also compares cooler used for cooling luxmeter sensor, the comparision is between measured values and created simulation.

The coldness of outer space is a huge thermodynamic resource that can be utilized as an infinite heat sink that helps in cooling terrestrial objects without the need for electrical energy through a phenomenon known as radiative sky cooling. In the last decade, radiative cooling has seen an increasing attention as a sustainable and clean cooling method and many researchers made smart use of it as a thermal management method. One example in the literature is the radiative cooling of solar cells. Like solar cells, Light Emitting Diodes (LEDs) are semiconductor devices that deteriorate because of high temperatures. Specifically, the high temperature in LEDs lowers their efficiency and lifetime. Therefore, reducing the temperature by increasing heat dissipation can help in optimizing the efficiency of the LED. In this work, I investigate a novel low-cost solution that can help in reducing the temperature of outdoor LEDs through radiative cooling. The suggested solution utilizes the coldness of outer space to radiatively cool the LED by using a layer of a visible-reflective-infrared-transparent material, nanoporous polyethylene (nanoPE), as a cover to reflect the visible light back to earth while transmitting infrared radiation to outer space. I theoretically discuss the potential cooling performance of LEDs in the suggested design and estimate a cooling power enhancement by 128 W/m2 in ideal conditions compared to current designs. In addition, I study the fabrication and characteristics of nanoPE and show how it can be used as a reflective/diffusive cover for LEDs. Lastly, I experimentally demonstrate the use of nanoPE as a cover for LEDs and show an LED temperature reduction of 15 ⁰C in the laboratory environment and 4 ⁰C outdoor and calculate a relative LED efficiency increase of 28% in the indoor scenario and 4% in the outdoor scenario. This efficiency increase can result in an energy saving of 2.2 TWh in the United States corresponding to at least 0.44 MMT CO2 emission reduction making this cooling solution attractive due to its low cost and high impact.

付記する学位プログラム名: 京都大学卓越大学院プログラム「先端光・電子デバイス創成学」 / 京都大学 / 新制・課程博士 / 博士(工学) / 甲第24624号 / 工博第5130号 / 新制||工||1980(附属図書館) / 京都大学大学院工学研究科電子工学専攻 / (主査)教授 川上 養一, 教授 野田 進, 教授 木本 恒暢 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

According to the U.S. Department of Energy, the energy consumption for lighting is estimated to be about 22% of the total electricity generated in the U.S for the year 2001. With the very poor conversion of electrical energy to visible radiation there is an immediate need to adopt new and efficient lighting solutions. Virginia Tech with its own commitment to reduce energy consumption is continuously looking and experimenting with the latest and most efficient lighting solutions for the interiors and exteriors of buildings on its campus. This study seeks to evaluate the performance of selected exterior and interior lighting solutions through experimental and simulation means. A proposed exterior lighting solution, for the "Hokie" light, the most common outdoor lamp fixture on campus, was monitored and evaluated under control settings in the Environmental Systems Laboratory at Virginia Tech. Options for improving the performance of the Hokie light and reducing the uplight were experimentally tested and analyzed. Use of a non-perforated aluminum LiteLid® was selected as the most promising and cost effective solution after analyzing the performance of a variety of options. For general interior lighting, the feasibility of using advanced lighting methods such as Light Emitting Diodes (LEDs) was explored and analyzed. The performance of LEDs was experimentally compared with the existing fluorescent lamps. Performances of the fluorescent and LED lamps were analyzed for selected parameters such as the quality, color and quantity of the light. The annual energy consumption and utility cost of a representative building on the Virginia Tech campus with existing fluorescent lamps and the proposed LED lamps was estimated using E-Quest simulation software. The building chosen for this purpose was the newly constructed Institute for Critical Technology and Applied Science (ICTAS). Low lumen output of the LED lamps and burnout due to heat dissipation and poor color rendition index (CRI) of the LED lamps makes them unviable for interior applications at this time. / Master of Science

Lighting consumes approximately 20-25% of the energy produced worldwide. LED based lighting is rapidly becoming the preferred choice over incandescent and fluorescent based lighting. LEDs have advantages such as high efficacy, long operating lifetime and excellent lumen maintenance. Therefore, to gain benefits from LEDs for lighting purposes, they must be driven with efficient drivers which maintain high LED efficacy and long LED lifetime. A review of existing LED drivers is done, and their advantages and drawbacks are identified. Existing fault-tolerant drivers are also reviewed. Several dimming methods and their effects on the LED efficacy and lifetime are investigated. As a result, a converter with coupled inductors, suitable as an LED driver which has high efficiency and can maintain high LED efficacy, incorporated with a high efficiency dimming method, is chosen. For the proposed LED driver, a comprehensive analysis on the effects of coupling type and coupling coefficient on converter performance is done. This is carried out to establish the best coupled inductor structure and coupling coefficient, for the proposed LED driver. The coupled inductor obtained is used to achieve high LED efficacy and also used to eliminate the need for an output filtering capacitor. This results in a highly compact, high efficiency and low cost LED driver. A lossless method of LED string current sensing is proposed, so that driver efficiency is not negatively impacted. The LED driver and a digital control system are designed, with the fault-tolerant feature incorporated. The LED driver and the control system are simulated and practically implemented. The results obtained show excellent LED driver performance. The fault-tolerant feature can enable the driver to operate under fault conditions, saving repair costs and down time. Additionally, a novel digitally controlled LED driver, which can drive several independent multiple LED loads, is proposed. This novel driver is simulated and practically implemented; with the results showing excellent driver performance. The novel LED driver can simplify and reduce costs of existing LED lighting systems. / Dissertation (MEng)--University of Pretoria, 2013. / gm2014 / Electrical, Electronic and Computer Engineering / Unrestricted

Depuis le début des années 2000, les performances des diodes électroluminescentes (LED) ne cessent de s’améliorer alors que leur prix connait une diminution spectaculaire grâce à une production à grande échelle liée au marché de l'éclairage. Ainsi, les LED deviennent une source de lumière intéressante pour le pompage de lasers solides, intermédiaire entre les lampes flash et les diodes laser. C’est pourquoi, nous proposons dans cette thèse, de revisiter le pompage laser par LED, 40 ans après la première démonstration. Nous avons démontré le premier système laser Nd:YVO4 pompé directement par LED. La brillance des LEDs limitant fortement les performances, nous nous sommes intéressé au concept de concentrateur luminescent (en Ce:YAG) pompé par LED. Nous avons ainsi développé une nouvelle source d’éclairage haute brillance, améliorant les performances des LEDs d’un facteur 20 pour aboutir à des éclairements comparables à ceux des diodes laser (de l’ordre de plusieurs kW/cm²). Le pompage laser par cette nouvelle source de pompage a été validé pour la première fois sur les cristaux laser de Nd:YVO4 (3 mJ obtenus avec un profil monomode et 6 mJ en multimode) ainsi que sur des cristaux de Nd:YAG. Dans ce dernier cas, un déclenchement passif à l’aide d’absorbants saturables a permis d'obtenir ainsi des performances encore jamais atteintes pour un laser pompé par LED. Ainsi, les concentrateurs pompés par LED ouvrent de nouvelles possibilités pour le pompage de matériaux laser nécessitant de forte brillance de pompage. Les premiers essais sur le saphir dopé au titane montrent qu'il est possible d'obtenir du gain sur ce matériau en pompage par LED. / Since the early 2000s, the lighting market is constantly growing up, pulling the Light-Emitting Diodes (LED) performance forward and pushing their cost down. LED is becoming an interesting source of light for laser pumping, between flashlamp and laser diodes. Thus, 40 years after the first demonstration, we suggest to revisit laser LED pumping. In this work, we demonstrated for the first time a Nd:YVO4 laser directly LED-pumped. LED radiance being limited, we took interest in LED-pumped luminescent concentrators. By developing Ce:YAG concentrator, we were able to overcome the LEDs irradiance by a factor of 20, leading to output irradiances similar to the laser diode ones (of the order of multi-kW/cm²). We validated the concept by pumping for the first time a Nd:YVO4 crystal and a Nd:YAG crystal with luminescent concentrators. Output energies of several mJ were obtained. In addition, we succeeded to get a passively Q-switched regime for the Nd:YAG laser by using saturable absorbers leading to unpreceded performance for a LED-pumped laser. Finally, LED-pumped concentrators pave the way for new possibilities for high-radiance source pumped media. Our first tests on titanium doped sapphire show that a laser gain with a LED pumping is achievable.

Light Emitting Diode (LED) is used in traffic signals and highway illumination in the Texas Department of Transportation, Houston District (TxDOT). The thesis focuses on the cost of maintenance of the LED for signals on the highway system in the Houston District. This LED cost includes human and capital resources which are compared against the cost associated with the incandescent bulb used in traffic signals at a similar location in Houston. The analysis leads to actionable decisions to see if total migration of the LED is advisable or not, amidst budgetary constraints and the benefits thereof. / text

This master’s thesis presents new tendency in automotive lighting – matrix LED headlamp. This thesis consists of description of matrix headlamp construction, main functions of matrix headlamp and controlling by using new integrated circuit, developed by ON Semiconductor Company. The aim of this project is concept of algorithm, which provides correct function of integrated circuit. A part of this thesis is to develop and assembly evaluation kit with this integrated circuit, which will be use to present integrated circuit for customers.

Master of Science / Department of Architectural Engineering and Construction Science / Fred L. Hasler / This paper discusses the potential of using LED modules as the primary light source for office buildings’ lighting systems. The LED lamps are the newest mass-produced lamps today; they have many insurmountable advantages compared to other light sources, like long lamp life, high efficacy, and low heat emission. Because of these advantages, owners and occupants of buildings can benefit greatly from the application of LED luminaires. The main focus of this paper is in 4 categories, which include the reliability of published data, occupant comfort, energy efficiency, and the life cycle costs of building lighting systems. LED light sources are compared to other primary light sources, which include fluorescent and incandescent lamps, of low ceiling office spaces from these 4 categories. The reliability of published data discussion covers color rendering index (CRI), correlated color temperatures (CCT), lamp life, and efficacy of the different type of lamps. The criteria of LED lamps are the most emphasized point of this section. The current CRI, efficacy, and lamp life evaluation systems are not suitable for LED lamps, and this paper discusses the practical value of each of these published data in office lighting system design. Some technical reports presented in this paper show that high CRI values of LED light sources do not directly link to excellent color rendition. However, LED light sources can have similar spectrum power distributions as natural light, and offer adequate visual comfort. Efficacy and lamp life are in the same situation. Even though, the published values do not necessarily reflect the real life performance of LED lamps, they often still have the longest lamp life and highest efficacy. Human comfort is the second factor discussed. Engineers and lighting designers consider illuminance level, color rendering ability, and glare of lighting systems to be deciding factors of human comfort from a lighting design perspective. However, many medical studies show that the human is much more sensitive to the correlated color of light sources. Light sources must vary output luminous flux and correlated color temperatures over time to help occupants reach optimum office task productivity and maintain health and visual comfort. LED lamps are the only light source that can practically change both the output luminous flux and correlate color temperature without heavy extra investments in equipment, which makes it the perfect candidate for this category. Energy efficiency is the third discussion point presented in this paper. Efficacy is a widely adopted term for evaluating the energy efficiency of a lamp, which describes the ratio of the output illuminance and input power. Because the output illuminance of LED lamps is decided not only by the illuminant bodies, but also many other electronic components in the lamps, some experts suggest that using efficacy to judge LED lamps is biased. This paper states the author’s position on whether efficacy can adequately describe the efficiency of LED lamps. Costs are also an inevitable point of this paper. LED lamps have the reputation of being the most expensive type of light source, but marketing data shows that the price of LEDs has been dropping dramatically recently. Moreover, Haitz’s law predicts that the price of LEDs will drop even more in the future. In this paper, the lifecycle costs of a light system have also been addressed across different types of light sources. Some crucial drawbacks of LED lamps, such as narrow photometric distribution and thermal damage control, are also addressed in this paper. Scientists and engineers still have not found the perfect solution to these drawbacks, but they are not significant enough to jeopardize the application of LED lamps in most architectural lighting design cases. According to the finding of this paper, LED lamps are the mainstream light source of future office lighting systems. The author also gives some suggestions for using LED lamps as primary light sources in office lighting system design applications at the end of the paper.