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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.

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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 seriesassociated 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.

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.