M. Cervi

Fluorescent lamp model based on the equivalent resistance variation

A circuit model simulating the electrical characteristics of a fluorescent lamp operating at high frequency is proposed. The model is based on exponential approximation that represents the equivalent resistance variation as function of power, constructed by experimental results for several power levels. Simulations and experimental results are presented to verify the feasibility of the model and, moreover, an electronic ballast example using the proposed model is presented to further demonstrate its applications.

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.

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 Family of Electronic Ballasts Integrating Power Factor Correction and Power Control Stages to Supply HPS Lamps

This paper presents a family of high power factor electronic ballasts applied to the public lighting system. Flyback, buck-boost, boost or SEPIC converter is employed in the power factor correction stage, integrated to the power control stage through a single active switch. The use of a half-bridge inverter, to supply the lamp, becomes possible through the employment of a flyback converter in the lamp power control stage. The lamp is supplied in a low frequency voltage square waveform in order to guarantee the safe lamp operation, regarding to the acoustic resonance phenomenon. The presented solutions to supply HPS lamps take the advantage of low cost and simplicity. The shared switch characteristics are analyzed and discussed during this work. A comparative analysis among the presented electronic ballasts is performed

Fluorescent lamp model employing tangent approximation

A circuit model simulating the electrical characteristics of a fluorescent lamp operating at high frequency is proposed. The model is based on exponential approximation that represents the lamp equivalent resistance variation as a function of power, constructed by experimental results for several power levels. Simulation results and experimental data are presented to verify the feasibility of the model and, moreover, an electronic ballast example using the proposed model is presented to further demonstrate its applications.

Electronic Ballasts for HID Lamps

This article presents a general analysis of several integrated topologies with high power factor in supplying metal halide (MH) lamps. The analyzed topologies that provide power-factor correction (PFC) are buck, boost, buck-boost, flyback, sepic, and zeta converters. The design methodology employed to calculate the circuit parameters and the simulation results are also presented.

An electronic ballast to supply automotive HID lamps in a low frequency square waveform

This paper presents an electronic ballast to supply a 35 W high intensity discharge (HID) xenon lamp for automotive applications. The ballast consists on a bidirectional flyback operating in discontinuous conduction mode (DCM) and an igniter circuit. The converter supplies the lamp in a 400 Hz square waveform and the igniter is responsible for providing the necessary voltage for lamp start up. The purpose of this work is to supply the xenon lamp from a 12 V battery with a reduced number of components, decreasing the system final costs without penalty the reliability. Some experimental results are presented to validate the proposed ballast behavior.

Analysis of the Output Capacitor and Lamp voltage Inversion for the Bidirectional Flyback Converter

This paper presents a lamp voltage inversion methodology and output capacitor analysis applied to a bidirectional flyback converter. The converter integrates the power control and the inversion stage, feeding a HPS lamp with a low frequency symmetrical square waveform, avoiding the acoustic resonance phenomenon occurrence. A detailed design of the lamp parallel capacitor is developed with parameters of stability, lamp power high frequency ripple and the lamp voltage inversion time to avoid lamp re-ignition. Experimental results are presented to validate the proposed topology.

Generalized Analysis and Comparison of High-Power-Factor Integrated Topologies to Supply Metal Halide Lamps with Low Frequency Square Waveform

This paper presents a generalized analysis of several integrated topologies with high power factor to supply metal halide lamps. The analyzed topologies that provide power factor correction are: buck, boost, buck-boost, flyback, sepic and zeta converters. These topologies are integrated with an output flyback converter to obtain the complete ballast. The output flyback converter is composed of one primary and two secondary windings that are switched at low frequency. In this way, the lamp is supplied with a low frequency square waveform, and acoustic resonances can be avoided. The proposed analysis makes use of the graft switch technique to obtain the different integrated topologies. The design methodology that can be employed to calculate the circuit parameters is also presented in detail. Finally, some simulation results are shown in order to confirm the design methodology and to compare the proposed integrated converters.

Integration Methodology of DC/DC Converters to Supply HPS Lamps: An Experimental Approach

This paper presents the integration of power stages in order to supply HPS lamps with a low frequency square waveform. This waveform is chosen to avoid the acoustic resonance phenomenon occurrence. Conventionally, the electronic ballast to supply the lamp in this way should have three power stages: power factor correction (PFC), power control (PC) and inverter. In this work, a methodology to integrate these power stages is defined. Seven different topologies are proposed and their experimental results are obtained in order to compare each one.