Ricardo Nederson do Prado

Compact Emergency Lamp Using Power LEDs

This paper presents a compact emergency lamp using light-emitting diodes (LEDs). The goal is to develop a compact and low-cost electronic circuit to drive and control the current of LEDs arranged in a single enclosure. The main advantage of the proposed idea is to use the same equipment in the daily activities, supplied by the ac line, and under a mains failure, supplied by a battery. The proposal also aims to achieve energy saving, higher luminous efficacy, and higher useful life when replacing traditional fluorescent-based emergency lighting systems. The use of the E-27 socket provides the advantage of easy installation, with the simple replacement of the lamp without any change in the electrical wiring. Buck and boost converters were employed in order to supply the LEDs by mains and by battery, respectively. However, the converters are designed in order to work without electrolytic capacitors, which have advantages such as reducing size and cost of the circuit, THD reduction, and increasing the useful life of the driver. The battery can be composed of three rechargeable Ni-MH batteries (1.2 V) or a Li-ion battery (3.6 V). The design complies with the Brazilian and international standards for emergency lighting systems and IEC 61000-3-2. The proposed circuit was implemented, and the experimental results were satisfactory.

An intelligent system for street lighting monitoring and control

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 These systems are considered outdated due the lack of communication capabilities, not allowing system feedback.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 an IEEE 802.15.4 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.

Analysis and Design of a Single-Stage High-Power-Factor Dimmable Electronic Ballast for Electrodeless Fluorescent Lamp

A methodological study of an electronic ballast for electrodeless fluorescent lamps (EFLs) including design and development issues is presented in this paper. The ballast is intended to feed a 100-W EFL at 250 kHz with dimming feature. The proposed topology is composed of a single-ended primary-inductance converter, used as power-factor (PF)-correction stage, integrated with a resonant half-bridge inverter, used as lamp-power control stage. The integration of both stages is proposed in this paper, in order to reduce the number of active switches, as well as to simplify the required driving and control circuitry for this application. Experimental results demonstrate the feasibility of the proposed solution that achieves 54% lamp-power dimming (46 W). The implemented topology attained very high PF (0.989) and low line-current total harmonic distortion (14.929%), without using electromagnetic interference filter, while the measured efficiency was 87% at nominal lamp power.

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.

Two Flyback-Based Integrated Converters for the Implementation of LFSW Electronic Ballasts

In this paper a new configuration of the two-flyback-based high-power-factor electronic ballast is proposed. The ballast is aimed to supply high intensity discharge (HID) lamps with a low frequency square waveform (LFSW), so that acoustic resonance (AR) phenomenon can be avoided. The proposed topology is compared to a previously presented one, which integrated the two flyback converters in a different manner. Therefore, this paper is focused on the comparison of both configurations by analyzing voltage and current waveforms and components stress. The proposed electronic ballast presents a high efficiency with a reduced number of components and no over current stress in the shared switch, which improves its efficiency. Experimental results validate both integrated configurations, but demonstrate a higher efficiency for the new arrangement proposed in this paper.

A geographic routing hybrid approach for void resolution in wireless sensor networks

Abstract: Geographic routing is one of the most suitable routing strategies for large scale wireless sensor networks due to its low overhead and high scalability features. A geographic routing scheme usually combines a geographic greedy forwarding with a recovery mechanism to solve the local minima problem. Solutions proposed in the literature commonly combine greedy forwarding with the well known face routing for achieving this goal. However, the average path length in number of hops produced by face routing could be much worse than the optimal topological path in most realistic scenarios. In this paper, we propose a new intermediate procedure between the geographic greedy mode and the recovery mode in order to improve routing efficiency in number of hops, without network overhead. It exploits the optimal topological route to base stations, obtained by beacon messages, as a resource to find better routes than the ones created by face routing. We show by simulations that the proposed hybrid approach leads to a significant improvement of routing performance when applied to combined greedy-face routing algorithms.

Design Methodology for Light-Emitting Diode Systems by Considering an Electrothermal Model

The knowledge about thermal, electrical, and photometrical characteristics of Light-Emitting Diodes (LEDs) is essential to achieve a good performance to the lighting system. This paper presents a methodology for designing LED systems. The main purpose is to provide an optimal operating point, considering the electrothermal design to achieve the maximum luminous flux for a given LED system. Based on two design routines, the proposed methodology brings the possibility to consider driver output current, heatsink size, and LED junction temperature in the system design. A mathematical analysis taking into account an LED electrothermal model is presented. Computational fluid dynamics simulation employing finite element method and experimental results validate the proposed methodology.

Feedforward Regulation Method for Self-Oscillating Electronic Ballast for Fluorescent Lamps

This paper presents a feedforward fluorescent lamp power regulation method for self-oscillating electronic ballast for different line voltages. The proposed method consists in maintaining the lamp power regulated through the feedforward switching frequency variation using the output resonant filter feature and self-oscillating gate driver circuit. Experimental results demonstrate the feasibility of the proposed solution that allows regulating the lamp power in a wide input voltage range (110 to 220 Vrms ) with an error of up to 12%.

Control network for modern street lighting systems

This paper proposes a control network for a LED street lighting system. The use of LEDs is being considered a promising solution to modern street lighting systems, due to their longer lifetime, higher luminous efficiency and higher CRI. The proposed control network enables disconnection of the street lighting system from the mains during peak load time, reducing its impact in the distributed power system automatically at overload conditions. It also allows to reduce the power consumption, decrease the management cost and monitor the status information of each street lighting unit. In order to meet the system requirements, a wireless sensor network based on IEEE 802.15.4™ standard is employed. Its network layer is implemented using geographic routing strategy, which provides low overhead and high scalability features. However, due to well known drawbacks of the existing techniques, a novel routing algorithm is proposed. Simulations show that this algorithm leads to a significant improvement of routing performance when applied to sparse large scale scenarios, which is the case of a street lighting system. Field tests have been performed on IEEE 802.15.4-compliant wireless control units. The obtained experimental results show that the proposed control network is able to meet the requirements of a LED street lighting system.

Digital Control Strategy for HID Lamp Electronic Ballasts

This paper presents the analysis, design, simulation and experimental results of a digital control strategy applied to an electronic ballast to supply a 70-W high-pressure-sodium lamp. The electronic ballast consists of a single-stage converter that integrates a buck converter to provide power factor correction and two flyback converters to supply the lamp, with low frequency square waveform, in order to avoid the acoustic resonance phenomenon occurrence. The proposed digital control strategy is composed of three control loops: voltage loop for lamp ignition and warm-up, an inner current loop for steady state, and a slow outer power loop to maintain the lamp power constant during its useful life. The lamp dynamic model is included to the ac model of the converter, so the effects of its right-half-plane zero are considered to design the digital control system. Fixed-point simulation is presented using Q base number format, where the exact variable values employed in the microcontroller code are used. Experimental results are included to demonstrate the performance of the proposed digital control strategy.