Cláudio R. B. S. Rodrigues

An experimental comparison between different technologies arising for public lighting: LED luminaires replacing high pressure sodium lamps

This work deals with the analysis and photometric comparison between different systems concepts for public lighting, hence the solid state lighting (SSL) employing LED luminaires with electronic drivers and the conventional high pressure sodium (HPS) lamp based luminaires along with electromagnetic ballasts. The study and comparison raise question on the relative perception of the human eye to different light sources with different spectral distributions, devoting special attention to low luminance conditions (scotopic) such as those present on public roadway lighting. Different LED-based luminaires are tested, in the lab and in loco. Photometric data of a SSL system being currently installed for the replacement of current HPS luminaires at the School of Engineering of the Federal University of Juiz de Fora are provided for the analysis and comparison.

A novel method of current equalization in LED strings based on simple linear circuit

This paper focuses on the problem of driving parallel strings of LEDs while ensuring current equalization between them. This issue is addressed in terms of proposing a small and simple linear topology that can be used on a number of series-associated LEDs, working as a constant current source for each string. Such topology employs a four-component circuit, with low dependence on transistor parameters, ensuring easy repeatability and good current regulation. Mathematical description of the circuit and experimental results are provided.

Experimental characterization regarding two types of phosphor-converted white high-brightness LEDs: Low power and high power devices

This paper describes an experimental photometrical analysis regarding two mainstreams inside the high-brightness LED family: the power devices, socalled high power LEDs, and the low power devices. Focus is given to white phosphor-converted LEDs, which are used in LED-based luminaires for indoor and outdoor lighting. Data from several LEDs used in available luminaires are compiled and provided as photometrical references for the design considerations in light output of LED drivers which employ power electronic converters.

Evaluation of lighting systems through adaptation of photometric quantities

The human eye presents different visual responses for different luminosity conditions. Thus, it can be defined different regimes of operation of the human visual system, like photopic and scotopic regimes, for high and low luminance levels respectively. All the classic photometry is based on the vision sensibility under the photopic regime. However, in several situations, it is common to face intermediate conditions known as mesopic. So, in order to convert photometric quantities between photopic and mesopic regimes, there is an equation in literature that describes the relationship between photopic and scotopic luminous fluxes as a function of the color correlate temperature. However, there are some evidences that this expression does not apply accurately to all technologies of light sources. Thus, this paper presents laboratory data showing that the equation in question does not apply to all lighting technologies, pointing towards a review of that relationship.

Single electronic ballast for HPS and HPMV lamp testing

This paper describes the analysis and design of an electronic ballast devised to drive both, high pressure sodium vapor (HPS) and high pressure mercury vapor (HPMV) lamps, in dimmed operation with no need of parameter modification. The main objective is to achieve weight and volume reduction of a public lighting components bench test equipment, used to perform basic operational tests in a Brazilian electric utility company. Specifically, the analysis, design and implementation of an electronic ballast, based on a series-parallel loaded resonant inverter, for 70W HPS and 125W HPMV lamps testing is presented. Experimental results from a lab prototype, performing high intensity discharge (HID) lamp tests in dimmed operation and no discharge arc instability, evidences the feasibility of the proposed ballast concerning the intended application.

Um estudo comparativo de sistemas de iluminação pública: Estado sólido e lâmpadas de vapor de sódio em alta pressão

This work deals with the viability analysis and photometric comparison between two different systems concepts for public lighting, hence the solid state lighting (SSL) employing high power LED luminaries with integrated electronic converters and the conventional high pressure sodium (HPS) lamp based luminaries along with electromagnetic ballasts. The study and comparison stem on the relative perception of the human eye to different light sources with different spectral distributions, devoting special attention to scotopic conditions of illumination. Photometric data of a SSL system being currently installed for the replacement of current HPS luminaries at the School of Engineering of the Federal University of Juiz de Fora is provided for the analysis and comparison.