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High-power light-emitting diodes (LEDs) and high-brightness LEDs have revolutionized the lighting industry. The availability of cost-effective LEDs with high luminous flux, efficacy, and reliability has expanded their application to replace incandescent and fluorescent light sources. They have also enabled many new applications that were considered infeasible before, due to the inherent limitations of traditional sources of light. This survey provides a comprehensive overview of ac- and dc-supplied LED lighting systems and their applications, corresponding specifications and their similarities to/differences from regular power supplies. Restrictions imposed by LEDs characteristics, safety considerations, and dimmers are discussed. Also, LED driving approaches are categorized and their suitability for different applications is provided.

This paper reports a study into the possibility of using LED systems of ultraviolet radiation for air ionization and disinfection of air and indoor surfaces in the presence of people. It has been established that UV LED lamps with 120° opening angles have parameters under which radiation intensity does not exceed 30 J/m2 at distances of 2 meters. Based on experimental data, a methodology for designing the placement of lamps in the room was devised, which meets the requirements of the SBM-2015 standard and the European Directive 2006/25/EU. The use of LED emitters with a total intensity of up to 25 J/m2 increases the concentration of aero ions. The background concentrations were 140‒180 cm-3 (positive) and 160‒190 cm-3 (negative). The minimum permissible level is 500 cm-3. As a result of irradiation, the concentrations were 1100‒1460 cm-3 (positive) and 1260‒1470 cm-3 (negative). The influence of the recirculator-air purifier on the concentration of aero ions has not been established. The ionization process began immediately after turning on the irradiation systems in the entire volume of the premises (4‒5 meters from the source). The dynamic equilibrium of aero ion concentrations was established within 10‒15 minutes after the irradiation was switched on. The presence of a large number of people (up to 0.97 m2 per person) did not affect the concentration of aero ions. Under the combined effect of ultraviolet radiation and a recirculator-air purifier, the number of mold fungi colonies decreased by 20 times. Under the influence of only ultraviolet radiation – by 2.3 times. The decrease in the number of microbes under the combined effect was 1.6 times, and under the effect of only ultraviolet radiation – 2.8 times [ABSTRACT FROM AUTHOR]

Human civilization revolves around artificial light. Since its earliest incarnation as firelight to its most recent as electric light, artificial light is at the core of our existence. It has freed us from the temporal and spatial constraints of daylight by allowing us to function equally well night and day, indoors and outdoors. It evolved from open fire, candles, carbon arc lamp, incandescent lamp, fluorescent lamp to what is now on our door step: solid state lighting (SSL). SSL refers to a type of lighting that uses semiconductor light-emitting diodes (LEDs), organic or polymer light-emitting diodes (OLED/PLED) as sources of illumination rather than electrical filaments, plasma (used in arc lamps such as fluorescent lamps), or gas. SSL applications are now at the doorstep of massive market entry into our offices and homes. This penetration is mainly due to the promise of an increased reliability with an energy saving opportunity: a low cost reliable solution. An SSL system is composed of a LED engine with a micro-electronics driver(s), integrated in a housing that also provides the optical, sensing and other functions. Knowledge of (system) reliability is crucial for not only the business success of the future SSL applications, but also solving many associated scientific challenges. In practice, a malfunction of the system might be induced by the failure and/or degradation of the subsystems/interfaces. This paper will address the items to ensure high reliability of SSL systems by describing LED degradation from a component and a system perspective. [ABSTRACT FROM AUTHOR]

Current imbalance among parallel light-emitting diode (LED) strings could put excessive current and thermal stress on some of the LEDs in the systems, resulting in reduction in system lifetime. For LED road lighting systems, reliability is the paramount factor. This paper first explains how existing current-mirror (CM) circuits cannot cope with LED open-circuit faults and then describes a self-configurable CM circuit that can withstand open-circuit faults in LED systems with parallel LED strings. The ability to withstand open-circuit faults means that the LED systems can still function with reduced luminous output even if one LED string is cut off. The proposed circuit, which retains the feature of not requiring an auxiliary dc power supply, has been practically implemented and successfully tested in a 70-W LED system with three parallel strings. [ABSTRACT FROM AUTHOR]

Reliability is an essential scientific and technological domain intrinsically linked with system integration. Nowadays, semiconductor industries are confronted with ever-increasing design complexity, dramatically decreasing design margins, increasing chances for and consequences of failures, shortening of product development and qualification time, and increasing difficulties to meet quality, robustness, and reliability requirements. The scientific successes of many micro/nano-related technology developments cannot lead to business success without innovation and breakthroughs in the way that we address reliability through the whole value chain. The aim of reliability is to predict, optimize and design upfront the reliability of micro/nanoelectronics and systems, an area denoted as 'Design for Reliability (DfR)'. While virtual schemes based on numerical simulation are widely used for functional design, they lack a systematic approach when used for reliability assessments. Besides this, lifetime predictions are still based on old standards assuming a constant failure rate behavior. In this paper, we will present the reliability and failures found in solid-state lighting systems. It includes both degradation and catastrophic failure modes from observation towards a full description of its mechanism obtained by extensive use of acceleration tests using knowledge-based qualification methods. A use case will be presented in more details. • In this paper, we will present the reliability and failures found in solid-state lighting systems. • It includes both degradation and catastrophic failure modes from observation towards a full description of its mechanism obtained by extensive use of acceleration tests using knowledge-based qualification methods. • A use case will be presented in more details. [ABSTRACT FROM AUTHOR]