Marcelo Freitas da Silva

An Intelligent System for Street Lighting Control and Measurement

One of the major challenges at the moment is the improvement of the present street lighting system. These systems are considered outdated due the lack of communication capabilities, not allowing system feedback. This work aims to add communication capabilities to the systems already in use, through the integration of a ZigBee™ compatible transceiver to the photoelectric relay used to turn the HPS lamps on/off. This change will turn each device into a node of a large wireless network across the city.

A new technique to equalize branch currents in multiarray LED lamps based on variable inductor

In this paper, a new technique to equalize light-emitting diode (LED) currents in multiarray LED lamps is proposed. The current through the LEDs is controlled by changing the inductance of a variable inductor. The proposed technique can be employed to control the current through each LED branch independently. The operation principle of this technique and a design example of the proposed system are presented in detail in this paper. As an example, a forward converter has been selected to supply the LED branches, which can be designed to operate with one or several outputs. The component values of the converter as well as the LED current control circuit are also calculated as a design example. A prototype of the circuit has been implemented. The experimental results obtained at the laboratory are satisfactory and in accordance to the proposed design methodology. The proposed technique can prove to be very cost-effective for LED drivers in the range of 100 W and beyond with multiple independent LED arrays.

Universal Input Voltage Self-Oscillating Electronic Ballast with Feedforward Control

This paper presents a universal input voltage electronic ballast supplying a 32 W fluorescent lamp. The electronic ballast is formed by a self-oscillating command circuit and an additional circuit. This circuit is used to guaranty the rated power of the fluorescent lamp through the voltage gain variation of the resonant filter. Thus, the switching frequency changes based on feedforward control to keep the nominal lamp power. Simulation and experimental results of the electronic ballast are presented to demonstrate the feasibility of the proposed system.

Comparison of single stage SEPIC and integrated SEPIC-Buck converter as off-line LED drivers

This paper presents comparison of single-stage Single Ended Primary Inductance Converter (SEPIC) and integrated SEPIC-Buck converter to drive Light Emitting Diodes (LED) in general lighting from a storage capacitance reduction point of view. Considering the low lifetime of electrolytic capacitors compared to that of LEDs, this study aims to compare which topology allows for using the smaller bus capacitance replacing it by a longer lifetime capacitor technology, increasing the overall system reliability. The analysis considers the same input/output parameters for both converters. The single-stage topology is a SEPIC operating in discontinuous conduction mode (DCM), which performs both power factor correction (PFC) and power control (PC) functions. In the integrated topology the PC stage is implemented by a Buck converter taking advantage of its output current source behavior, suitable for LED application. The design and implementation allows for a quantitative analysis between both topologies. The single-stage topology requires a 2.119 mF storage capacitance and achieves 85.12% efficiency, while the integrated topology requires a 187.5 μF storage capacitance and attains 83% efficiency for the same input/output parameters.

An integrated insulated buck-Flyback converter to feed LED's lamps to street lighting with reduced capacitances

This paper presents the project of an integrated insulated converter to feed a LEDs lamp to street lighting systems. An integrated Buck-Boost-Flyback was designed, as well a control technique to reduce the capacitances value and the paper also presents the parameters and experimental results of the integrated converter.

An integrated insulated Buck-Boost-Flyback converter to feed LED's lamps to street lighting with reduced capacitances

This paper presents the project of an integrated insulated converter to feed a LEDs lamp to street lighting systems. An integrated Buck-Boost-Flyback was designed, as well a control technique to reduce the capacitances value and the paper also presents the parameters and experimental results of the integrated converter.

Conception and design of a lighting system based on Light Emitting Diodes for spectrum simulation

This work aims to develop an electronic system based on Light Emitting Diodes (LEDs) to emulate a reference light spectrum. Light Emitting Diodes are used due to their well-known advantages over other light sources. As an example of application, this work focuses on the design and implementation of a solid-state solar simulator whose spectrum resembles the natural daylight to support research on photosynthetic organisms. The system design and a spectrum optimization process are presented. Mixed Integer Programming (MIP) is adopted to set the optimal amount of LEDs that result in the most accurate response. The study of the LED spectrum, power converters for LED driving and control are discussed.

Dimmable Single-stage Sepic-buck Converter For Led Lighting With Reduced Storage Capacitor

This paper presents an analysis and design of a Light Emitting Diode (LED) driver aiming to eliminate/substitute the electrolytic capacitors. Considering the low lifetime of electrolytic capacitors compared to LEDs, this topology aims for reducing the storage capacitance and replaces it by a film capacitor, increasing the system lifetime. This reduction is based on designing of the control dynamic with a compromise between the input current distortion and the output current ripple. The power factor correction (PFC) stage is based on a Single Ended Primary Inductance Converter (SEPIC) because of its intrinsic low input current distortion characteristic making it possible to eliminate the electromagnetic interference (EMI) filter. The power control (PC) stage is performed by a Buck converter using its output current source behavior, suitable for LED application. A 100 W LED driver prototype is implemented resulting in a 6.9% total harmonic distortion (THD) and 30% current ripple on the LED.

LED Lamp with a Compact Emergency Lighting System

This paper presents an efficient and compact emergency lighting system using high intensity light emitting diodes (LEDs). The proposal aims energy saving, high luminous efficacy and high useful life when replacing traditional emergency lighting systems and incandescent or compact fluorescent lamps by LEDs without any change in electrical system installation. A Buck converter is used to supply the LEDs and charge the battery by mains, with universal input voltage (90 VAC - 240 VAC), and a Boost converter is used to supply the LEDs by battery. The converters operate at high frequency and control the LEDs current independently. A Li-Ion battery was chosen because it has higher voltage and density of energy than Ni-MH one. The design attends the Brazilian standard (NBR 10898) and IEEE standard (IEEE Std 446-1995) for emergency lighting systems. The complete circuit was implemented and the experimental results show a satisfactory behavior of the lamp.

Universal input voltage self-oscillating electronic ballast based on switching frequency control

This work presents a universal input voltage electronic ballast supplying a 32 W T8 fluorescent lamp. The electronic ballast is formed by a self-oscillating command circuit and an additional circuit. The additional circuit is used to guaranty the rated power of the fluorescent lamp through the voltage gain variation of the resonant filter. Thus, the switching frequency changes based on feedforward control to keep the nominal lamp power. Simulation and experimental results of the electronic ballast are presented to demonstrate the feasibility of the proposed system.