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In order to increase the power density and the lifespan of light-emitting diodes (LED) drivers, several studies have proposed active ripple compensation (ARC) techniques for minimizing the converter bulk capacitance. However, a common side effect of the ARC method is the increase in the total harmonic distortion (THD) of the converter input current. In this context, a frequency-based ARC technique is proposed as an alternative to the conventional ARC methodology, in which the duty cycle is modulated. The analyses presented in this article show that the frequency-based ARC approach applied to resonant converters has a better performance than the one used in hard-switching converters, since it allows for a huge capacitance reduction with a small THD increase. Furthermore, this article presents a generalized analysis of ARC techniques applied to integrated offline LED drivers, which reduce the number of components and the overall LED driver cost. The input current harmonic content and the output ripple reduction have been theoretically predicted for several converters. Experimental results gathered from a 96-W laboratory prototype supplied from a 127-V 60-Hz grid attested the superior performance of the frequency-based active ripple compensation, since a capacitance reduction of 66.6% has been obtained with an increase of only 0.9% in the THD. [ABSTRACT FROM AUTHOR]

Nowadays, there are few commercial types of ballasts that are able to control fluorescent lamps with different power ratings. One of the main issues is how to get optimum operation for each lamp in this condition. This paper tries to demonstrate how to accomplish this objective using a magnetic regulator, i.e., using a variable inductor. This variable inductor is controlled by a dc current delivered by a forward converter directly supplied from the ballast dc bus voltage. This control current allows changing the resonant tank and adapting it to the working parameters imposed by each lamp, ensuring near-resonance working conditions. Design criteria and practical verifications are included to confirm this new technique. Theoretical predictions are verified with the experimental results for three TLD Philips fluorescent lamps, from 18 to 58 W. Index Terms--Fluorescent lamps, half-bridge inverter, magnetic regulators, resonant tank, universal ballasts, variable inductance.

Discharge lamps present a negative dynamic characteristic that makes necessary to use a current limiting element. In high-frequency resonant ballasts, current limitation is performed by the output resonant tank; but in low-frequency square-wave electronic ballasts, arc stabilization is accomplished by the stage feeding the square wave inverter. Therefore, the design of the input converter must be made taking into account the lamp dynamic characteristic. In the present paper, a new procedure to obtain the small-signal dynamic characteristic of metal halide lamps is proposed. Using the proposed methodology, the small-signal characteristic of a 70-W lamp is obtained. This characteristic is then used for the design of an electronic ballast based on a buck-boost converter followed by a full bridge inverter. The limits for stable operation obtained are verified using a laboratory prototype. Index Terms--Arc stabilization, electronic ballasts, metal halide (MH) lamps.

In this paper, a study about acoustic resonance (AR) in low-wattage metal halide lamps is presented. The lamps are supplied with a typical low frequency square waveform on which a high frequency sinusoidal ripple is superposed. The goal is to emulate the same waveforms generated by a low frequency electronic ballast. In this way, the ARs that appear in the lamp can be characterized against ripple amplitude and frequency. Different lamp's manufacturers and burning hours are used. The obtained results are intended to be employed in further reliable designs of low-frequency square-waveform electronic ballasts. An example of application of the accumulated AR signatures in this type of electronic ballasts is carried out, and a standard proposal is presented. Index Terms--Acoustic resonance (AR), electronic ballast, metal halide (MH) lamp, square waveform operation.

In this paper, a simple method to obtain the small-signal model of discharge lamps, and particularly metal halide (MH) lamps, is proposed. A dc voltage source with a series resistor is used to supply the lamp at the required power level. Then, the lamp response against an input voltage step transient is analyzed. From this analysis, the parameters of the equivalent lamp model can be calculated. The proposed method allows obtaining the lamp model in a straight manner from a single test. With this technique, a 35-W MH lamp is modeled at two different power levels. A validation circuit, which includes a resistive ballast and a capacitance, is analyzed to evaluate the possibilities of the proposed modeling technique. The obtained experimental results are in good agreement with the theoretical analysis. The derivation of a time domain lamp model for SPICE-based computer simulators is also introduced. Finally, an example of application in low-frequency square-waveform electronic ballasts is presented. Index Terms--High intensity discharge (HID) lamp, low-frequency square-waveform (LFSW), metal halide discharge (MHD) lamp.

A non-resonant electronic ballast based on one power switch and on one reactive element-one inductance-is described in this paper. The special current mode control implementation provides an intrinsic short-circuit protection and a very simple control circuitry. Filament heating time, current during the heating period, and protection against broken tube can be easily implemented with the proposed circuitry. A greenhouse application with a 120-V dc bus power distribution is presented in this paper. The dc bus voltage is easily obtained (in this particular application) from a classical series-connected 12-pulse rectifier in combination with a transformer with two secondary windings (one in Wye connection and other one in Delta connection). An additional advantage of this configuration is the high power factor obtained at the input stage. Index Terms--Boost inverter, current mode control, electronic ballast, fluorescent lamp, greenhouse lighting.

A novel single-stage high-power-factor electronic ballast obtained from the integration of a buck dc-to-dc converter and a half-bridge resonant inverter is analyzed in this paper. The buck converter is operated in discontinuous conduction mode and at constant frequency providing an input power factor high enough to satisfy present standard requirements. The operation of the proposed ballast is also investigated in detail in this paper, obtaining the important equations and characteristics in order to allow interested readers to perform an easy design. A ballast prototype supplying two 36 W fluorescent lamps has been both simulated and implemented at the laboratory. The results predict good market possibilities for the proposed topology in terms of reliability, cost, efficiency, and lamp life. Index Terms--dc-to-dc converter, discontinuous conduction mode, electronic ballasts, half-bridge resonant inverter.

This paper proposes a single-stage electronic ballast for high-intensity discharge lamps. The ballast consists of the integration of a boost converter in discontinuous conduction mode (DCM) and a full-bridge LCC resonant inverter. The boost semi-stage working in DCM functions as a power factor corrector and the inverter semi-stage operated above resonance is employed to drive the lamp. The sine-wave approximation is used to design the inverter at steady-state. The proposed electronic ballast can save a controller, reduce size and possibly increase system reliability compared to conventional two-stage system. The proposed ballast is analyzed, simulated and experimentally verified with a 125 W HPS lamp. Index Terms--Electronic ballast, high-intensity discharge lamps, power factor correction, resonant inverter.

This paper presents some design issues and experimental results regarding the use of the input current shaper (ICS) technique to implement high power factor electronic ballasts. The ICS is placed between main rectifier and bulk capacitor to increase the conduction angle of the main rectifier diodes up to a minimum value to obtain low current harmonics injected to the mains. Two possibilities to implement ICS-based ballast are considered in this paper: the forward-based ICS and the flyback-based ICS. Experimental results obtained from two 40-W fluorescent lamp ballasts are also presented. Index Terms--Fluorescent lamp, high-frequency operation, input current shaper, power factor correction, single-stage ballast.

A complete study of the clamped-mode (CM) series-parallel (LCC) resonant inverter together with some of the control-to-output characteristics are presented in this paper. Also, a new control method for the CM LCC resonant inverter is introduced. With this method, the inverter is forced to operate with optimum commutations and without handling reactive energy, thus minimizing both switching and conduction losses. The corresponding design procedure is illustrated with a design example. Finally, some experimental results obtained from a prototype at the laboratory are also shown to validate the analysis and evaluate the proposed control method. Index Terms - Clamped-mode series-parallel resonant inverter, high-intensity-discharge lamp ballast, lighting, low-losses control method, optimum commutations, soft switching.

A new single-stage high-power-factor electronic ballast based on a flyback converter is presented in this paper. The ballast is able to supply a fluorescent lamp assuring a high-input power factor for the utility line. Other features are lamp power regulation against line voltage variations and low lamp current crest factor, both assuring long lamp life. The ballast is analyzed at steady-state operation, and design equations and characteristics are obtained. Also, a procedure for the ballast design is presented. Finally, simulation and experimental results from a laboratory prototype are shown. Index Terms-- Dimming, electronic ballast, high frequency, lamp power regulation, power factor correction, single-stage converter.

A foreword to the May 2007 issue of "IEEE Transactions on Power Electronics" is presented.