Tiago B. Marchesan

A practical comparison among high-power-factor electronic ballasts with similar ideas

This paper provides a comparative analysis among four electronic ballast topologies with high power factor, employing the same switch for inverter and power factor correction stage. The analyses done are based on experimental results. A commercial electromagnetic ballast (EMB) is tested to provide a comparison with implemented electronic ballasts. The features of each topology are shown through the discussion of their advantages and disadvantages. The electronic ballasts are made for two 40-W fluorescent lamps at 50-kHz switching frequency and for a 110-V/sub rms/ 60-Hz utility line.

Capacitance Reduction With An Optimized Converter Connection Applied to LED Drivers

This paper presents a new control method and a detailed project methodology for the optimized connection method of two converters, aiming to reduce the redundant power processing, in order to supply high-power light-emitting diodes (LEDs) with reduced capacitance and high efficiency, directly from the ac line. This connection method allows dealing with two major issues related to the LED driver: capacitance reduction and efficiency increasing. The first converter provides power factor correction, whereas the second converter controls the current through the LED. The basic idea consists in making the second converter to process only the low-frequency ripple (LFR) of the first converter, thus smoothing the LED current. In this way, the LFR is managed by the second stage, so that the capacitance of the first stage can be significantly reduced. The proposed control method can achieve better results for the low-frequency compensation. In addition to that, a high power factor and a low harmonic content are obtained, fulfilling the IEC 61000-3-2 Class C requirements. A laboratory prototype with a rated power of 75 W and an input voltage of 220 Vrms/60 Hz was built in order to show the feasibility of the idea. The measured overall efficiency of the converter was 91%, and electrolytic capacitors were avoided.

Integrated Zeta–Flyback Electronic Ballast to Supply High-Intensity Discharge Lamps

This paper proposes a metal halide lamp electronic ballast based on the integration of zeta and flyback converters, which are used to achieve power factor correction and lamp current stabilization, respectively. The proposed integrated converter allows to reduce the number of ballast components without increasing the current stress in the shared switch. Thus, the lamp is supplied with a low-frequency square waveform that avoids the acoustic resonance phenomenon. The proposed topology has been implemented and validated by experimental results.

Static and Dynamic Photoelectrothermal Modeling of LED Lamps Including Low-Frequency Current Ripple Effects

In this paper, a static and dynamic photoelectrothermal model including the impact of low-frequency current ripple on light-emitting diodes (LEDs) performance is proposed. The objective of this study is to evaluate the dynamical interaction among thermal, photometrical, and electrical properties of the LEDs when they are supplied by a dc constant current with a superposed low frequency sinusoidal ripple, which is the common case in offline LED drivers. Therefore, this paper presents both a model and experimental data for analyzing the LED photometrical behavior in terms of luminous flux, efficacy, flicker, and chromaticity. Three laboratory prototypes with different heat sinks and LED models have been tested. Experimental results are presented to evaluate the LED photometrical behavior under the aforementioned operating conditions and to validate the proposed modeling methodology.

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.

Solid-State Lighting: A Concise Review of the State of the Art on LED and OLED Modeling

This article presents an overview of technologies for solid-state lighting (SSL). In recent years, light-emitting diodes (LEDs) have developed characteristics desirable for lighting applications. The success of these light sources for general lighting depends on the system design, which comprises an understanding of electrical and photometrical characteristics under the temperature effect on device performance. This review focuses on the main theoretical models for the characterization of SSL devices, regarding the electrical and thermal aspects to reach the desired photometrical characteristic for a lighting system. An approach about inorganic LEDs and organic LEDs (OLEDs) will be presented along with the application of these devices in SSL systems.

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 semiconductor lighting system controlled through a LIN network to automotive application

This paper proposes an intelligent lighting system for bus interior environment using LEDs (light emitting diodes) controlled through an automotive communication network. The system consists on a master central control and slaves lighting modules, using a LIN (local interconnect network) network to perform communication. This network is a low cost alternative to the proposed system requirements, due to its low bit rate and physical needs. The slaves are independent lighting modules that supply a group of LEDs and measure the environment lighting level. The master sets LEDs module parameters (slaves), such as the state (on/off), and desired lighting level The master makes the user interface, sets the lighting parameters, as timer and lighting level and, more over, it establishes communication with other bus systems through a CAN (controller area network) gateway. This paper presents a complete logical description, including block and state diagrams, a physical description and some relevant experimental results.

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.

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.