High-power white light-emitting diodes (LEDs) have attracted much attention due to their versatility in a variety of applications and growing demand in markets such as general lighting, automotive lamps, communications devices, and medical devices. In particular, the need for high reliability and long lifetime poses new challenges for the research and development, production, and application of LED lighting. Accurate and effective prediction of the lifetime or reliability of LED lighting has emerged as one of the key issues in the solid-state lighting field. Prognostic is an engineering technology that predicts the future reliability or determines the remaining useful lifetime of a product by assessing the extent of deviation or degradation of a product from its expected normal operating conditions. Prognostics bring benefits to both LED developers and users, such as optimizing system design, shortening qualification test times, enabling condition-based maintenance for LED-based systems, and providing information for return-on-investment analysis. This paper provides an overview of the prognostic methods and models that have been applied to both LED devices and LED systems, especially for use in long-term operational conditions. These methods include statistical regression, static Bayesian network, Kalman filtering, particle filtering, artificial neural network, and physics-based methods. The general concepts and main features of these methods, the advantages and disadvantages of applying these methods, as well as LED application case studies, are discussed. The fundamental issues of prognostics and photoelectrothermal theory for LED systems are also discussed for clear understanding of the reliability and lifetime concepts for LEDs. Finally, the challenges and opportunities in developing effective prognostic techniques are addressed.

A Review of Prognostic Techniques for High-Power White LEDs

A simple graph with four nodes and eleven branches is defined. Its branches are filled in different ways with passive elements (capacitors, inductors, diodes) or replaced by shortcircuits in order to get potential voltage step-up switching cells. These cells are inserted in boost converter, obtaining thus non-isolated power electronics circuits with a very high dc gain. Such circuits are necessary today in the green energy systems. The proposed circuits feature a lower voltage stress on its semiconductors (both switch and diodes) than that on the equivalent devices of a boost stage. A state-space-based dc and ac analysis allows for deriving the dc gain, the switches voltage and current stresses, and the frequency characteristics of the obtained converters. The steady-state analysis is performed for both the continuous and discontinuous conduction mode operations. The converters belonging to the new family are compared between them and then compared with available solutions of similar complexity as defined by the component count. Simulation and experimental results confirm the theoretical equations.

Generation of a Family of Very High DC Gain Power Electronics Circuits Based on Switched-Capacitor-Inductor Cells Starting from a Simple Graph

Street lighting characterizes many smart city initiatives around the world. In fact, significant savings can be achieved by not only replacing traditional luminaires with low-power LEDs, but also providing streetlights with smart light controllers and network connectivity, allowing the introduction of a sensible light intensity management and reduction of maintenance costs. Moreover, if designed with a far-looking view, smart lighting infrastructure could also support city-wide Internet of Things services, becoming key enablers of the smart city revolution, also in the 5G perspective. In this paper, we provide a thorough discussion on network architectures and communication technologies that could be adopted for smart public lighting applications, showing their benefits and downsides. Starting with significant activity on research, implementation and in-field testing, we also outline the steps required for the deployment of a smart public lighting infrastructure, each discussed in accordance with the network topology considered. Finally, we introduce some additional services that a smart public lighting infrastructure could support and discuss the benefits that would arise from integration with the upcoming 5G cellular network.

https://www.mdpi.com/2076-3417/9/16/3281/pdf

Design, deployment and evolution of heterogeneous smart public lighting systems

Light-emitting diodes (LEDs) are solid-state devices with specific $v$ – $i$ characteristics. In this paper, we study the basic requirement of the driving circuits and discuss the proper approach to drive LEDs in view of their characteristics. We compare voltage source driving and current source driving, and discuss their relative advantages and constraints. We specifically introduce the use of circuit duality principle for developing new current-source-mode (CSM) drivers that are less known but are theoretically more versatile compared to their conventional voltage-source-mode counterparts. The study highlights the effects of the choice of driving circuits in terms of the number and size of circuit components used, duty cycle variation, sensitivity of control, nonlinearity and control complexity of LED drivers. We propose a CSM single-inductor multiple-output (SIMO) converter, which demonstrates the advantage of having inductorless and easily controlled current-source drivers, and present a comparison of the CSM SIMO converter with the existing SIMO converters. We further illustrate that a high-voltage-step-down ratio can be naturally achieved by the CSM high-voltage-step-down converter without the use of transformers. This paper presents a systematic and comparative exposition of the circuit theory of driving LEDs, with experimental evidence supporting the major conclusions.

/pdf/basic-circuit-theoretic-considerations-of-led-driving-579jxk5mq8.pdf

Basic circuit theoretic considerations of LED driving: Voltage-source versus current-source driving

A first approach to universal daylight and occupancy control system for any lamps: Simulated case in an academic classroom

Abstract For the modern smart lighting systems one of the most attractive LED advantages is the dimming possibility. Many researchers and engineers from the field of lighting engineering are trying to find compromise between the efficiency of LED dimming process and the ease of its implementation. This paper also presents an attempt to improve LED dimmer parameters. Comparative investigation of the operation of buck LED drivers in continuous conduction mode and discontinuous conduction mode are discussed here. The first section of paper briefly describes the controllability parameters of the converter in both of these modes. The positive impact of discontinuous conduction mode on the controllability parameters as well as the results of the analytical estimation and the results of associated experiments are summarized at the end of the first section. The second section describes the impact of discontinuous conduction mode on the losses of LED dimmer. The analytical estimation of power losses in the main converter components for both operation modes as well as the summary of the experiments to identify distribution of power losses between these components are presented in this section. Finally, the conclusions about using discontinuous conduction mode for dimmable LED lamps as well as guidelines for the choosing of the components with the most appropriate parameters are drawn

/pdf/dimmable-led-drivers-operating-in-discontinuous-conduction-4svnbhba95.pdf

Dimmable LED Drivers Operating in Discontinuous Conduction Mode

The given paper deals with equipment for smart lighting systems. A hypothesis, that current fed dimmable electrical ballasts with amplitude modulation of light could improve the controllability of such systems, is brought forward. Since there are very few natural current sources it is proposed to use a combination of a voltage source, switch mode voltage-to-current converter and current regulator. The first part can be built as a buck converter, while the regulator is similar to a boost converter. Together this gives a topology known as non-inverting buck-boost converter which, however, in the given case has to be controlled as two modules of “current source” nature. The control rules suitable for such strategy are discussed in the paper. In order to verify the idea a laboratory prototype of such converter has been built and tested. The features of the converter are given in the paper below. The obtained results show that the idea works in general, but certain instability and efficiency problems have to be solved. That is why it was concluded that a more accurate control method for the voltage-to-current source part has to be developed.

Validation of direct current control in LED lamp with non-inverting buck-boost converter

Energy saving importance is growing year-to-year and effective lighting is considerable part of overall consumption reduction Modern light sources (LED based lamps) are much less consuming than traditional ones Furthermore, the saving can be increased, by implementing smart lighting control systems over theses lamps High initial costs set investment bounds on wide use of systems of this kind The main elements that give LED lamp smart functionality are: 1) dimmable driver; 2) communication module; 3) sensor/s (ambient light, movement, gas etc); 4) controller This paper gives the insight on cost reduction by integration of microwave motion sensor in LED lamp to build a smart system

Integration of microwave sensor into low cost indoor LED lamp — Element of smart lighting system

This paper is an attempt of authors to consider most likely scenario of the further development of street lighting systems, based on current trends in sensors, telecommunication technology and auto industry. Street lighting system previously already was considered as the element of the Smart City by researchers, however, the precise functionality, role and the importance of such a system was considered rather mediocre (ordinary). This article is a holistic view of the Smart Street management system with the street lighting system, which plays great importance of whole transportation and mobility infrastructure functionality and safety enhancement.

Potential Role of Street Lighting System for Safety Enhancement on the Roads in Future

The high power LED driver based on non-inverting buck-boost converter is considered in this paper. The special regulation approach of this converter is described in order to simplify the control strategy. Thus, the implementation of this control strategy in microcontroller based closed loop regulation system allows to increase number of regulation steps (to achieve higher resolution) and to utilize timers of the microcontroller in more efficient way. Also the considerations on the configuration of MOSFET gate driver circuits are given in the paper.

Olegs Tetervenoks

Papers

Dimmable LED Drivers Operating in Discontinuous Conduction Mode

Validation of direct current control in LED lamp with non-inverting buck-boost converter

Integration of microwave sensor into low cost indoor LED lamp — Element of smart lighting system

Potential Role of Street Lighting System for Safety Enhancement on the Roads in Future

The study of microcontroller based embedded system for smart lighting applications