Marcelo R. Cosetin

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.

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.

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.

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.

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 Systematic Approach to Modeling Complex Magnetic Devices Using SPICE: Application to Variable Inductors

In this paper, a methodology to develop SPICE-based models of complex magnetic devices is presented. The proposed methodology is based on a reluctance equivalent circuit, which allows the user to study both the magnetic and electric behavior of the structure under any operating conditions. The different elements required to implement the reluctance model, namely, constant reluctances, variable reluctances, and windings, are implemented using SPICE behavioral modeling. These elements can thus be used to build a complete model for any magnetic device. The modeling process is illustrated with a particular example for a variable inductor. Simulations and experimental results are presented and compared to evaluate the accuracy and usefulness of the proposed modeling procedure.

Long-lifetime SEPIC-buck integrated converter for LED lighting application

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.

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.

Off-line single-stage SEPIC-Buck converter for dimmable LED lighting with reduced storage capacitor

This paper presents an analysis and design of a Light Emitting Diode (LED) driver aiming to 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 longer lifetime capacitor, increasing the overall system life span. A Proportional Integral (PI) controller is designed to reduce the output current ripple. Consequently, it reduces the bus voltage which allows working with reduced bus capacitances. The input current distortion limit must be observed. The power factor correction (PFC) stage is based on a Single Ended Primary Inductance Converter (SEPIC) operating under discontinuous conduction mode (DCM) because of its 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 107 W LED driver prototype is implemented resulting in 15.2% total harmonic distortion (THD), 50% current ripple on the LED and an efficiency of 90.1% using a 35μF bus film capacitor. Furthermore a dimming strategy is proposed and implemented by an LED parallel active switch.