Fernando J. Nogueira

An experimental study on the photometrical impacts of several current waveforms on power white LEDs

Since light-emitting diodes (LEDs) are a rising lighting technology, a great amount of research is currently being focused on driving techniques for these current-fed semiconductor devices. For realizing efficient current drivers, power electronics is usually employed. This work focuses on studying the impacts that several high and low frequency current waveforms commonly found on power electronic drivers may have on the photometrical and colorimetrical performance of the LEDs themselves. Empirical evidence obtained under controlled experiments is provided to correlate important features of the LEDs to the current levels and waveforms.

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.

Street lighting LED luminaires replacing high pressure sodium lamps: Study of case

This paper deals with the study of the pilot project of street lighting using LED luminaires on the campus of Federal University of Juiz de Fora. Over twenty nine months the system was monitored in order to evaluate the performance of this technology that is gaining ground in the lighting industry. Photometric and electrical results obtained during this period will be presented as well as a comparison with the old lighting system that employs high-pressure sodium lamps based on classical photometry and mesopic photometry, which takes into account the dynamic visual response of the human eye. In addition, will be done a simplified economic analysis aiming to show the saving generated by the new lighting system and a calculation of payback of the new luminaires.

Street lighting LED luminaires using telemanagement systems: Study of case

The main purpose of this paper is to analyze the performance of LED luminaries and to analyze the remote management integrated into them. These luminaires come with a remote monitoring system based on ZigBee protocol, and it allows wireless communication using GSM / GPRS, the most used technology around the world provided by mobile network operators. With photometric tests, electrical and performance analysis of the luminaires in according to the standards, this paper aims to study the operation of the whole system in a pragmatic way and to evaluate the actual performance and the possible positive and desired results on the public lighting system.

A comparative study regarding linear fluorescent and LED lamps for indoor lighting

A study methodology aimed to compare two low power lamp technologies, T8 fluorescent and linear T8 LED lamps, is presented. Electrical parameters and temperature measurements are compared as well as an analysis of the obtained results from digital simulations concerning photometric characteristics. A new method for measuring photometric parameters is proposed to replace the current standards. A payback retrofit study concerning LED technology to be applied in a typical educational building is also given.

Simplified control techniques applied to a boost-based low frequency offline LED driver

This paper presents an offline LED driver based a low-frequency boost converter and its application to street lighting luminaires. The analysis of the boost pre-regulator is revised and two simplified methods of microcontrolled control are proposed. Experimental results are shown to an LED luminaire operating in 165W.

Modeling And Control Of A Low Frequency Offline Led Driver Based On Boost Pre-regulator

This work presents the state-space average modeling of the low frequency off-line LED driver based on the boost pre-regulator converter with an LC filter output. The small signal modeling of the converter was derived. A control strategy of the current through the LED arrangement is also proposed. The converter was designed to supply power to a street lighting LED luminaire. The LED driver prototype was able to present a high power factor (PF) and a low total harmonic distortion (THD). The output power of the LED driver was 186 W with 93 % efficiency, when fed by 220 V, 60 Hz mains. The modeling presented in this paper aimed to seek a more precise derivation of the control to output transfer function, i. e., the transfer function concerning the output current and the duty cycle switch parameter. The paper also provides details of the frequency domain design of the current compensator by employing the improved transfer function. The compensator must perform two main tasks, which are the output luminous control (dimming feature) and the rejection of input voltage disturbances. In addition, the compensator transfer function was discretized for future implementation in a microcontroller. Simulation results of the digital compensator in open-loop and closed-loop are presented to validate the small signal modeling and to observe the dynamic response of the proposed compensator.

Design of a transformeless high power factor low frequency LED driver applied to street lighting

This paper presents a discussion about the use of a low frequency boost pre-regulator as offline LED driver and its application to a street lighting LED luminaire. This simple and low cost converter may provide high power factor, low input current distortion, high efficiency and compliance with IEC 61.000-3-2 Class C standard, which limits the emission of harmonic currents of lighting equipment. The analysis of the boost pre-regulator is revised. Computational simulation and experimental results are shown to an LED luminaire operating in 155W. In this case, no transformers and electrolytic capacitors are required, which define higher converter efficiency and an extended lifetime for this driver.

Low frequency led driver based on the Ćuk converter applied to street lighting luminaires

This paper presents a discussion about the use of a low frequency Ćuk-based pre-regulator as an offline LED driver and its application to a street lighting LED luminaire. This simple AC-DC converter may provide high power factor, low input current distortion and compliance with IEC 61.000-3-2 Class C standard, which limits the emission of harmonic currents of lighting equipment. Computational simulation and experimental results are included regarding an LED luminaire adopting 48 high power LED unities associated in series. In this case, no transformers neither electrolytic capacitors are required, which define an extended lifetime for this driver. Moreover, the proposed LED driver can make use of conventional choke inductors employed in nowadays HID-ballasts. Authors believe that this feature will contribute to reduce the solid waste thrown away to the environment, since it is expected a boom on the use of LED luminaires for outdoor lighting at the near future.