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In this paper, a new technique to equalize light-emitting diode (LED) currents in multiarray LED lamps is proposed. The current through the LEDs is controlled by changing the inductance of a variable inductor. The proposed technique can be employed to control the current through each LED branch independently. The operation principle of this technique and a design example of the proposed system are presented in detail in this paper. As an example, a forward converter has been selected to supply the LED branches, which can be designed to operate with one or several outputs. The component values of the converter as well as the LED current control circuit are also calculated as a design example. A prototype of the circuit has been implemented. The experimental results obtained at the laboratory are satisfactory and in accordance to the proposed design methodology. The proposed technique can prove to be very cost-effective for LED drivers in the range of 100 W and beyond with multiple independent LED arrays. [ABSTRACT FROM AUTHOR]

This paper presents a comparative investigation, design and development issues about six different single-stage topologies, applied as electronic ballasts, for electrodeless fluorescent lamps. The ballast is intended to feed a 100 W lamp at 250 kHz, with dimming feature. The proposed topologies use different converters for the power factor correction (PFC) stage: Buck-Boost, SEPIC, Zeta, Cúk, Flyback, and Boost. All of them operate in discontinuous conduction mode. A resonant half-bridge inverter is used as lamp power control (PC) stage. The integration of both stages (PFC and PC) is proposed in this paper. In this way, it is possible to reduce the number of active switches, as well as simplify the required driving and control circuitry. Experimental results demonstrate the feasibility of the proposed dimming technique that achieved around 56% lamp power dimming, from 100 W down to 44 W. The implemented topologies attained high average power factor (>0.98), and low line current average total harmonic distortion (<;15.3%). A comparison among all the proposed topologies in terms of power factor, harmonic distortion, efficiency and number of components is presented. Finally, a comparison between an integrated and a nonintegrated SEPIC half-bridge converter is also performed. [ABSTRACT FROM AUTHOR]

This paper presents an electronic ballast for driving high intensity discharge (HID) lamps with low frequency square waveform from a dc supply. From the dc source (e.g., PFC rail), a flyback arrangement is inserted into a switching structure whose output provides low frequency voltage yet avoiding instability issues. Proposal's main advantage is the use of one single choke of simple assembly and only two active switches for current control and inversion. Converter design for DCM is presented in this work, besides an equivalent circuit from a control point of view. Small signal ac model is obtained and a feedback control loop is designed, based upon frequency response stability and performance analysis. HID dynamics is inserted into converter model, with feedback directly implemented. A prototype is presented and described in detail, consisting of a complete power and sensing circuit fully referenced to the switches common ground proposal. For design conformity, experimental and simulation results from Matlab and PSIM are presented, as well as discussions about the converter feasibility. [ABSTRACT FROM AUTHOR]

In this paper, the variable transformer solution is presented as a step forward in magnetically controlled electronic ballasts. The proposed technique takes advantage of the device's equivalent series inductance to provide a new flexible way for lamp's luminous flux regulation. Output electrical isolation and constant frequency operation are also guaranteed by the proposed realization. A simple method for large-signal characterization of the variable transformer is described. An FH 14W/840 Osram lamp was chosen to validate this new technique and experimental results clearly show its adequate behavior. [ABSTRACT FROM AUTHOR]

In this paper, a digitally controlled electronic ballast is presented. The ballast corresponds to the so-called universal or multiwatt ballasts, which are intended to operate different lamps with different power ratings without performing any change in the hardware. Thus, the ballast must incorporate some kind of circuitry so that the rated power of the connected lamp can be identified. The ballast must also adjust some of its parameters in order to supply the lamp adequately, which usually means the following: 1) as close as possible to the nominal power and 2) with the best efficiency. In the proposed ballast, the parameters selected to adapt the power circuit to each lamp are the switching frequency and the resonant tank inductance. The resonant tank inductance is varied by means of a magnetic regulator whose inductance can be adjusted through a dc bias current. Due to the relatively high complexity of the proposed converter, a digital control circuit is developed to control both the resonant inverter used to drive the lamp and the dc–dc converter employed to supply the control winding of the magnetic regulator. Experimental results from a laboratory prototype for lamp powers ranging from 15 to 58 W are provided. [ABSTRACT FROM AUTHOR]

Due to the high rise in luminous efficiency that high-brightness light-emitting diodes (HB-LEDs) have experienced in recent years, many new applications have been researched. This paper covers a streetlight LED application using the offline integrated buck–flyback converter (IBFC) developed in previous works. In this application, the converter is used to provide power-factor correction from a universal ac source. A control loop using the LM3524 IC has been implemented for testing the feasibility of Enabling pulsewidth modulation dimming mode. First, the LED load has been linearized and modeled in order to calculate the IBFC topology properly. Second, the converter has been designed and tested at the laboratory. The converter has also been modeled in order to design a fixed-frequency constant-current control. The dynamics of all the stages involved in the closed loop have been taken into account in order to develop an adequate controller. Finally, the experimental results obtained from the laboratory tests are discussed. [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. [ABSTRACT FROM AUTHOR]

This paper presents a comparative analysis and experiments of resonant tanks for magnetically controlled electronic ballasts, focusing on their behavior and performance when driving hot cathode fluorescent lamps. Four different resonant tanks are analyzed: LC, LCC, capacitive impedance inverter, and CLL. The analysis is performed using a 36-W fluorescent lamp, which has been previously tested and modeled experimentally. The lamp model is used to derive the dimming characteristics of the different resonant tanks when using the resonant inductance as a control parameter. Analysis and experiments showed that instabilities appear when the lamp power is decreased below a minimum value, which effectively limits the dimming range of the ballast. Nevertheless, the proposed control method can be used to control lamp power in an adequate range provided that the resonant tank should be selected and designed properly. [ABSTRACT FROM AUTHOR]

In this paper, a new control method for electronic ballasts based on the use of a variable inductor is presented. The main goal is to perform the complete control of the electronic ballast by maintaining the switching frequency constant and without using other parameters of the power converter, such as input voltage or duty cycle. The magnetic regulator is controlled by means of a dc current, which allows performing both lamp soft starting and lamp dimming. Apart from the important advantage of keeping a constant frequency during full electronic ballast operation, the proposed method presents additional advantages when compared to other control methods, such as inherent isolated control, more linear control characteristics, constant electrode power, and higher efficiency. Experimental results from a 36-W linear fluorescent lamp prototype are presented. [ABSTRACT FROM AUTHOR]

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. [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]

In this paper, a detailed study and experimentation on acoustic-resonances (AR) in low-wattage metal-halide lamps is presented. In order to excite the AR without extinguishing the electric arc, the lamps were supplied by means of a dc current with a superposed variable-frequency ac signal. By using this methodology, theoretical and experimental resonances were compared in terms of frequency, amplitude, and threshold-power level for their excitation. The experiments were carried out on four 35-W samples from each manufacturer (Osram and Philips), each of them with burning times of 100, 2500, and 5000 h, in order to cope with the full life of this type of lamps. AR maps for each lamp were obtained. These maps show not only the frequencies at which AR appear but also the amplitude of the resonances. The obtained AR maps are intended to be used by designers in order to know if a particular instantaneous lamp power waveform would be suitable to supply the lamp without generating AR. An application example on how to use these maps is also 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]

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.

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.

The analysis and design of a dimmable electronic ballast based on the class E amplifier and fed from solar cells with 12V backup batteries is described. The class E amplifier uses a capacitive impedance inverter as resonant tank and one diode antiparallel with the switch; these elements allow implementation of a dimming feature for the ballast and ignition of the lamp while maintaining zero voltage commutations in the switch. The designed electronic ballast drives a 21W lamp and operates at a switching frequency of 370kHz. Dimming is implemented using an SG3524 in a voltage-controlled oscillator fashion. [ABSTRACT FROM AUTHOR]

Presents information on a study which evaluated a single-stage high-power-factor electronic ballast based on a flyback converter. Steady-state analysis; Simulation and experimental results; Conclusions.

Presents a novel single-stage constant-wattage high-power-factor electronic ballast. Schematic diagram of the ballast's circuitry; Steady-state analysis of the ballast; Equivalent circuits of the ballast during one cycle of operation.

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. [ABSTRACT FROM AUTHOR]