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Abstract-The use of high-efficiency LEDs in low-power lighting applications is growing continuously due to new advances in LED features. The lifetime of a low-power fluorescent lamp is around 5000 h. This implies short lamp-replacement times and high maintenance costs. The use of high-efficiency LEDs reduces drastically the maintenance costs due to the long lifetime (>50000 h). One of the applications where using LED is very interesting is permanent emergency light systems. Generally, these circuits are based on a two-stage design, using two magnetic cores. This paper presents offline power LED driver and battery charger integrated in one magnetic core topology. Besides, the converter allows driving the LEDs in case of a line failure and it complies with the IEC 61000-3-2 Class C Standard. [ABSTRACT FROM AUTHOR]

Usually, pulsewidth modulation (PWM) operation is selected as the best dimming strategy to drive high-brightness LEDs. Nevertheless, to obtain an enhanced full linear dimming control of the device, the luminous flux should be measured. This paper proposes a control method based on an estimator of the luminous flux emitted by the LED. Based on the characterization of the LEDs, this estimator is defined. The estimator provides the flux value from Only two temperature values (the case temperature and the ambient temperature). Once the estimator is validated, the electronic driver to supply the LEDs, as well as the digital control scheme, are presented. Such a control scheme is suitable for both AM and PWM dimming strategies. A prototype of the electronic driver has been built and tested, and experimental measurements of AM and PWM dimming are presented. It can be concluded that with the proposed estimator, the flux emitted by the LEDs can be accurately estimated. Thus, the output light control of the LEDs can be accomplished by sensing temperature rather than luminous flux. The final output characteristic of the system shows linearity between the output flux and the reference value, with AM as well as with PWM dimming of the LEDs. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

High intensity discharge (HID) lamps are the most suitable when both high light power levels and good color rendering are researched. Some remarkable theoretical advantages would be obtained if these kinds of lamps were driven with high frequency (HF) electronic ballasts. Nevertheless, at these frequencies, acoustic resonances (AR) phenomenon appears. Low wattage metal halide (MH) lamps are, among all HID lamps, the most affected by this phenomenon. To obtain lack of AR in HID lamps, lamp power frequency harmonics must have a lower amplitude than a certain threshold value, related to activation energy. An electronic ballast may be designed to guarantee power harmonics levels lower than this threshold level at nominal operation. Nevertheless, the equivalent resistance of HID lamps varies highly in starting and warm-up stages, as well as in the aging process. Therefore, the system must be designed to be adequate for the necessary "supplying conditions" for these load variations. In this paper, a new control strategy for a HF square-wave inverter is presented. This ballast keeps lamp power harmonics at low levels, regardless of the lamp equivalent load. The proposed ballast, along with the control strategy, is presented, as well as the built prototypes and experimental results carried out. From these experiments, it can be concluded that the proposed method supplies low wattage MH lamps with lack of acoustic resonances. [ABSTRACT FROM AUTHOR]

Currently, the main drawback in high-intensity discharge lamps supplied by means of high-frequency (HF) electronic ballasts are the so-called acoustic resonances. In this paper, two HF nonresonant inverters for low wattage metal halide (MH) lamps are analyzed, from the point of view of its behavior regarding the acoustic resonances' phenomenon. Thus, a HF electronic ballast, operating with a lack of acoustic resonances, is proposed. From a dc voltage bus, the inverters provide an ac waveform to the lamp. The power stage operation of the inverters is first analyzed. Then, the characteristics of these waveforms are analyzed, from the point of view of minimizing the acoustic resonances' appearance. Then, upon these theoretical results, a comparison between inverters is done, selecting the most appropriate for lighting purposes. After that, a built prototype of the chosen inverter topology is presented, and the experimental results are shown. These experiments were carried out on several 70-W MH lamps. Finally, some conclusions are presented. [ABSTRACT FROM AUTHOR]

In this paper, a low-cost power control for LCC series-parallel inverters with resonant current mode control for high intensity discharge (HID) lamps is presented. These resonant inverters require controlling the power supplied to the lamp in order to avoid exceeding the maximum lamp power recommended by the lamp manufacturer. The classical control method measures the lamp voltage and current and they are multiplied analogically, obtaining the lamp power consumption measure. This control circuitry results very complex due to the lamp voltage and current wide variations range during ignition and discharge processes. Assuming a regulated input dc voltage (bus voltage) provided by the power factor correction (PFC) pre-regulator and an inverter constant efficiency along the lamp aging, the lamp power consumption may be estimated and regulated properly measuring the inverter average input current. Also, the small-signal analysis performed allows obtaining the small-signal resonant inverter input impedance and studying the connection stability between PFC pre-regulator and inverter. The inverter small-signal analysis has been performed and an electronic ballast prototype for 250-W HPS lamps has been implemented and tested verifying the low-cost lamp power control method proposed. [ABSTRACT FROM AUTHOR]

In this paper, the optimum design of the LCC parallel-series inverter with resonant current mode control for 250-W high pressure sodium vapor lamps is presented. With this control method the inverter does not have any reactive energy, and both switching and conduction losses are minimized. Also, the design proposed performs a precise natural power control without exceeding the maximum power recommended by the lamp manufacturer without additional lamp power control circuitry. Since it is desirable implementing a low-cost and efficient power factor correction (PFC) stage for meeting the standard IEC 61000-3-2 Class C about low-frequency harmonic content injected in the line for lighting applications, a low-cost PFC buck pre-regulator is proposed. The ignition process is optimized because no additional circuitry is necessary for the lamp ignition providing low ignition inverter current. The design proposed leads to an important size and cost reduction, avoiding the additional circuitry used in the classic designs. Simulations and experimental results have validated the design proposed in this paper. [ABSTRACT FROM AUTHOR]

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 the 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. [ABSTRACT FROM AUTHOR]

Presents a study that proposed a single-stage electronic ballast for high-intensity discharge lamps. Description of the derivation of the proposed topology; Presentation of the steady-state analysis; Details of the general design procedure.

Focuses on a study that presented some design issues and experimental results regarding the use of the input current shaper (ICS) technique to implement high power factor electronic ballasts. Input current shaper characteristics and implementation; Steady-state analysis and design issues; Design examples; Experimental results.

Studies the clamped-mode (CM) series-parallel (LCC) resonant inverter together with some of the control-to-output characteristics. Introduction of a control method for the CM LCC resonant inverter; Methodology used to conduct the study; Findings of the study.