Rafael A. Pinto

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 These systems are considered outdated due the lack of communication capabilities, not allowing system feedback.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

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.

Compact Lamp Using High-Brightness LEDs

This paper proposes a circuit for a compact lamp based on high-brightness LEDs. It aims energy savings, high luminous efficacy and high useful life when substituting incandescent or compact fluorescent bulbs for LEDs without any change in the electric system installation. In order to supply the LEDs by mains with a forward current, the Buck converter has been chosen. The load can be composed by 36 to 52 LEDs of 5 mm connected in series, resulting in a converter output voltage between 90 V and 187 V. The advantage of series connection is that all LEDs produce the same brightness since its luminous intensity is proportional to the supplied current. The disadvantage is that the damage of one LED could results in an open-circuit, turning off the entire group. To fix this problem, the proposed idea on this work is the introduction of Diacs connected in parallel with groups of LEDs. So, if one LED burns the breakdown voltage is reached, and the Diac in parallel with this group become a short- circuit guaranteeing the operating of the others groups. To verify the proposed idea, the compact lamp has been implemented and tested.

A Review on Variable Inductors and Variable Transformers: Applications to Lighting Drivers

This paper presents a literature review on magnetically-controlled devices, variable inductors and variable transformers, and their applications in lighting gear. It describes the fundamentals and basic operating principle of such devices. Then, it focus on the review of specific techniques and circuits taking advantage of the presence of a controlled inductance value, by covering recent applications regarding discharge and solidstate lamp drivers.

High-power-factor street lighting system to supply LEDs without energy consumption during the peak load time

This paper presents two topologies for street lighting system with high power factor (HPF) based on light emitting diodes (LEDs). The main characteristic of this work is to develop a circuit that supplies the LEDs by an alternative source (battery) during the peak load time (PLT). The peak load time is considered as the period in which the demand for power from the mains is maximum, and therefore the generation of the power plants and transmission lines must be able to meet this demand. In this work, a bidirectional flyback converter with two outputs is used to supply the LEDs from the mains and also to charge the battery. One topology uses an auxiliary winding to supply the LEDs from the battery. The other uses the same primary winding to supply the LEDs from the battery or from the mains. The flyback converter is composed of a single core for both topologies. Besides, a buck converter is used as Power Factor Correction (PFC) stage. The integration of these converters is performed in order to reduce the number of components and consequently, the volume and cost of the circuit. The converters were implemented and experimental results are shown in order to validate the design methodology, and to compare both topologies.

A bidirectional buck-boost converter to supply LEDs from batteries during Peak Load Time

This paper presents a design methodology for a street lighting system based on light emitting diodes (LEDs) without energy consumption from the mains during the Peak Load Time (PLT) that uses batteries to supply the circuit during this period. Besides, when a failure on the mains occurs, the batteries can keep the system working as an emergency lighting system. The decrease in energy demand from the generation power plants and transmission lines, and the reliability improvement of the street lighting system (SLS) justify these applications. The use of LEDs for lighting applications presents benefits owing to its long useful life added to its high luminous efficacy, high color rendering index and directional light emission. In this system, a single DC-to-DC converter (buck-boost) supplies the LEDs from the mains, and also from a battery when necessary. The proposed system has high efficiency, high power factor, and complies with the IEC 61000-3-2 standard.

Design procedure for a compact lamp using high-intensity LEDs

This paper proposes a circuit to a compact lamp based on light emitting diodes (LEDs). It aims energy savings, high luminous efficiency and high useful life with the replacement of incandescent or compact fluorescent lamps by LEDs without any change in the electrical system installation. In order to supply the LEDs by mains with a constant current, the Buck converter has been used because it provides an output voltage lower than the input one. The circuit has been designed to supply 36 to 52 high-brightness LEDs connected in series, resulting in a converter output voltage between 90 V and 187 V. The load can also be composed of power LEDs. The main disadvantage of series connection is that the damage of one LED can results in an open-circuit, disconnecting the entire group. The proposed idea to solve this problem is the introduction of Diacs connected in parallel with groups of LEDs. So, if one LED burns, the Diac in parallel with this group keeps the current path, guaranteeing the operation of the others groups. To verify the proposed idea, prototypes of the lamp have been implemented and tested.

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.

Single-stage high-power-factor dimmable lighting system for electrodeless fluorescent lamp

The use of the electrodeless fluorescent lamps has been increasing, because of their features such as lifetime and lumen efficiency, when compared to conventional fluorescent and high pressure sodium lamps. The single-stage high-power-factor electronic ballast for electrodeless fluorescent lamp with dimming feature is presented on this paper. It is obtained by integrating a SEPIC converter with a Half-Bridge asymmetric LCC resonant inverter, which can effectively regulate the lamp power. Experimental results are shown, in order to validate the proposed idea. The implemented topology presented a power factor of about 0.995, a total current harmonic distortion of 9.61% and an efficiency of 86%.