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Even though, nowadays, piezoelectric transformers (PTs) are only available with low power rating, there exist several low-power applications of ozone generation in which the use of this novel technology could be advantageous. Hence, the aim of this paper is to evaluate the possibilities of using PTs in the implementation of high-voltage power supplies for ozone generation. First, the possible topologies that can be used to drive the PT are identified. Then, the half-bridge inverter operating under zero-voltage switching (ZVS) is investigated, and the effect of the silent discharge generator (SDG) on the converter operation is analyzed. A new control circuit that allows the ZVS operation is proposed. The control circuit operates in dosed loop by measuring the phase between the PT's resonant current and the switching pattern and adjusting the switching frequency to the optimum value to assure ZVS. A laboratory prototype for a 6-W SDG was tested, and obtained experimental results are shown. Index Terms--Control method, half-bridge inverter, high frequency, ozone generation, piezoelectric transformer (PT), Rosen-type PT, zero-voltage switching (ZVS).

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. Index Terms--Electronic lighting, high-brightness LEDs, light dimming.

Summary: Zero‐voltage‐switching boundaries of dual‐active‐bridge (DAB) converter operating with phase‐shift modulation is largely studied in literature. However, several practical considerations are neglected to simplify the ZVS analysis. This paper proposes the full analysis of DAB converter ZVS range considering the switches capacitance, dead time, series inductance design, and input/output voltage variation. Three different designs of series inductance were developed. The prototypes were tested under different voltage conditions considering the whole power range. The experimental results show the considerable difference in ZVS region of the classical analysis and the proposed in this paper, proving the feasibility of the paper analysis. [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. Index Terms--Dimming, electronic ballast, fluorescent lamp, magnetic regulator, resonant tanks, variable inductance.

In this paper, a novel single-stage electronic ballast with a high power factor is presented. The ballast circuit is based on the integration of a buck converter to provide the power factor correction, and a flyback converter to control the lamp power and to supply the lamp with a low-frequency square-waveform current. Both converters work in discontinuous conduction mode, which simplifies the control. In spite of being an integrated topology, the circuit does not present additional stress of voltage or current in the main switch, which handles only the flyback or buck current, depending on the operation mode. To supply the lamp with a low-frequency square-wave current to avoid acoustic resonances, the flyback has two secondary windings that operate complementarily at a low frequency. The design procedure of the converters is also detailed. Experimental results from a 35-W metal halide lamp are presented, where the proposed ballast reached a power factor of 0.95, a total harmonic distortion of 30 % (complying with IEC 61000-3-2), and an efficiency of 90%. Index Terms--Acoustic resonance (AR), electronic ballast, high power factor (HPF), integrated buck flyback converter, metal halide lamp (MHL), single stage (SS).

This paper investigates the integrated buck-flyback converter (IBFC) as a good solution for implementing low-cost high-power-factor ac-dc converters with fast output regulation. It will be shown that, when both buck and flyback semistages are operated in discontinuous conduction mode, the voltage across the bulk capacitor, which is used to store energy at low frequency, is independent of the output power. This makes it possible to maintain the bulk capacitor voltage at a low value within the whole line voltage range. The off-line operating modes of the IBFC are also investigated to demonstrate that the control switch of the proposed converter handles lower root-mean-square currents than those in similar integrated converters. The off-line operation of the IBFC is analyzed to obtain the design characteristics of the bulk capacitor voltage. Finally, the design and experimental results of a universal input 48 V-output 100 W ac-dc converter operating at 100 kHz is presented. Experiments show that the IEC-61000-3-2 input current harmonic limits are well satisfied and efficiency can be as high as 82 %. Index Terms--Fast output regulation, integrated buck-flyback converter (IBFC), low cost, low current stress, power factor correction, single-stage (SS) ac-dc converter.

In this paper, a new control strategy that allows zero-voltage-switching (ZVS) operation of power converters using piezoelectric transformers (PTs) is proposed. The control circuit operates in a closed loop by measuring the phase between the PTs resonant current and the switching pattern and adjusting the switching frequency to the optimum value so that ZVS operation is assured. An innovative nonlinear regulator based on an analog multiplexer is presented. The regulator automatically swaps the signs of the sensed signal and the reference signal to allow generation of the adequate control action. A laboratory prototype for a 6 W resonant inverter was tested; obtained experimental results are also shown. Index Terms--Control circuit, half bridge converter, piezoelectric transformer (PT), power supply, zero-voltage-switching (ZVS).

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. Index Terms--Dimming, electronic ballast, fluorescent lamp, high frequency, magnetic regulator, soft start, variable inductor.

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 nmnber 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. Index Terms--Acoustic resonance (AR), ballast, high-intensity discharge (HID) lamps, integrated circnits, power electronics.

The use of high frequency (HF) square waveforms is a possible metal halide (MH) lamps supply method which can be implemented by means of non-resonant electronic inverters. This strategy can successfully avoid acoustic resonances appearance in such kind of lamps (theoretically, in a perfect square waveform, no power modulation is found). The main drawbacks of this kind of inverters are the electromagnetic interference emissions and the parasitic effects of the series igniters. This effect can spoil the square waveforms on the lamp, hence injecting HF harmonics in the lamp supply power spectrum, eventually leading to acoustic resonances appearance. In this paper, this effect is studied, in order to limit the values of the parasitic elements of the series igniter compatible with a proper operation of the HF inverter. Once these values are estimated, such an igniter has been built and tested, thus obtaining a practical HF (100 kHz) square waveform inverter with series igniter for 35-W MH lamps. Index Terms--Acoustic resonances, high frequency (HF) transformers, metal halide (MH) lamps, series igniters, square waveform inverters.

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.

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. Index Terms--Acoustic-resonance (AR) characterization, AR maps, electronic ballast, high frequency, metal-halide (MH) lamp, power harmonics.

In this article, an integrated parallel buck–boost and boost converter (IPB3C) is proposed as an electrolytic-capacitor-less light-emitting diode (LED) driver. The IPB3C provides a high power factor (PF) and low total harmonic distortion (THD). The driver is composed of two converters that are connected in parallel, using just one controlled switch. The buck–boost duty is to deliver constant power to the LED, while ensuring a good PF. The boost converter is employed to cancel the low-frequency ripple at the LED. In return, this decreases the flicker effect and only a relatively small capacitance is needed to fulfill the standard requirements. The buck–boost converter handles the full power of the LED, while the boost converter handles only a portion of the LED power. Thus, better efficiency is ensured by this parallel configuration compared to conventional cascaded integrated converters. Moreover, the voltage across the switch is low, as it is the higher, whether buck–boost or boost converter, but not the addition of both. In this article, the IPB3C is analyzed, and its design methodology is presented. A universal input voltage range prototype of the proposed converter supplying an LED lamp of 108-V/ 0.35-A is presented. The prototype shows high PF, nearly equal to one, very small THD, nearly zero, output voltage ripple of 4.5%, output current ripple of 19%, and high efficiency, equal to 92.4%. Moreover, the converter requires the use of a bulk capacitance of only 68 μF, while the required output capacitance is just 1 μF. [ABSTRACT FROM AUTHOR]

This article presents a deep analysis of the low-frequency ripple transferred from the bus voltage to the light-emitting diode (LED) current in integrated two-stage power converters, operating as offline LED drivers. This analysis presents a design methodology to select the optimum power control stage converter to the LED load and to reduce the bulk capacitance. The main focus is to analyze the ripple transfer ratio of the three main nonisolated dc–dc converters, namely buck, boost, and buck–boost. Moreover, this article presents a step-by-step case study for an existing converter and the proposed converter supplying a 26.9-W Luxeon 3014 LED load. The experimental results show that the integrated buck and boost converter requires a bus capacitance of 1200 μF, whereas in the integrated buck and buck–boost converter, the capacitance is reduced to 680 μF by applying the method proposed. This represents that the replacement of a boost converter by a buck–boost converter on the second stage allows a 50% reduction of the bus capacitance while keeping the same current ripple. [ABSTRACT FROM AUTHOR]

This letter presents a fluorescent-lamp improved arrangement in the half-bridge topology, putting one lamp in each branch of the converter. This arrangement allows a multilamp independent behavior. So, if one lamp is damaged, the other one keeps on working. In order to prove this independent arrangement, experimental results of one electronic ballast supplying two lamps with different wattage were shown. Index Terms--Fluorescent, lamp arrangement, multilamp.

In this article, a high-power-density off-line light-emitting diode (LED) driver is proposed. The proposed ac–dc driver is the novel integrated buck and boost converter (IBBC). Besides the high-power-density, the converter shows a high power factor (PF), and a low total harmonic distortion (THD). The IBBC is a two-stage driver that features just one controlled switch, which leads to high PF and low THD operation ensuring high efficiency, and size and cost reduction. Moreover, the switch current is minimized as it conducts the higher of the buck or boost converter, but not the addition of both as in other integrated converters. Moreover, for a further increase of the power-density, a magnetic integration is made by integrating the two inductors of both the buck and boost converters in one core. Thus, the proposed converter has been named as fully integrated buck and boost converter (FIBBC). In this paper, the IBBC is analyzed, and a design methodology is proposed. Also, this article presents a magnetic analysis of the novel FIBBC. In addition, a comparison between two prototypes is presented, one for the IBBC and another for the FIBBC, both of them supplying an LED luminaire of 46 V/ 0.575 A. The FIBBC shows a high PF equal to 0.994, very small THD of 10%, output current ripple of 6%, and efficiency of 92.62%, which represents a landmark on the efficiency of integrated converters. [ABSTRACT FROM AUTHOR]

In this study, the analysis of the quad-U variable inductor (VI) is presented. This is an alternative structure of VI to other ones previously presented and analysed in the literature, as for example the double-E structure and the triple-E structure. Compared to them, the quad-U structure shows some advantages, namely more symmetrical operation and zero voltage reflected across the bias winding. The superposition law is applied to the equivalent reluctance model in order to solve for DC and AC operation separately. Using the proposed methodology, both AC winding inductance and DC winding inductance can be obtained. An example of analysis is presented for a particular quad-U VI. Simulation and experimental results prove the validity of the proposed analysis and modelling methodology. [ABSTRACT FROM AUTHOR]

This paper presents a study of the losses in the integrated buck–flyback converter (IBFC) used as high-power-factor LED driver. The aim of the study is to investigate the possibilities of increasing the efficiency of the IBFC converter. The procedure of the improvement is done by obtaining the equations of the current through each component in terms of converter parameters. The current is found in an average value or rms value, depending on the type of the parasitic component, whether it is modeled by a parasitic forward voltage source or by a parasitic resistance, respectively. Using these equations and the parasitic model, the losses of each element of the converter are estimated. This paper proposes a technique to increase the efficiency of the IBFC by redesigning the converter parameters. Furthermore, this paper presents a case of study with a step-by-step efficiency enhancement process of an existing driver. The driver is operating under universal input conditions, and 38 V output, supplying an LED luminary of 26.5 W. The new design shows an improvement of the efficiency from 82% in the old design to 89% in the proposed one. Moreover, the new design shows an improvement in the power factor and the THD and a 50% reduction in the output current ripple. Furthermore, a reduction in the number of components has been achieved, as it is found by the analysis that by adjusting the converter parameters, one diode can be removed. Finally, the presented methodology is explained in detail so that it can easily be applied to other dc–dc converters. [ABSTRACT FROM AUTHOR]

This paper presents the analysis and experiments of a variable inductor (VI) based LED driver for dc grid lighting applications. The proposed driver requires only a series inductor and a transformer as major components to drive the LED lamp from a half-bridge inverter. By introducing a VI as the series inductor, the LED current can be controlled independently from any other parameter, which makes it possible to drive and regulate several LED branches from the same half-bridge output. Other advantages of the proposed converter include inherent open-circuit and short-circuit protections, zero-voltage switching for the bridge transistor and zero-current switching for the output rectifier diodes, simple dynamics, possibility of analog and pulse width modulation dimming, constant switching frequency operation, and high efficiency. The converter is thoroughly analyzed and modeled for both steady-state and dynamic operation. As another novelty of this paper, the dynamic response of the VI has been studied and taken into account to obtain the complete transfer function of the VI-controlled system. In addition, some housekeeping issues that usually arise when dealing with VI, e.g., how to drive the VI bias winding, are solved in this work. Experimental results provided from a 50 W laboratory prototype demonstrate the correctness of the performed analysis and the good possibilities of the proposed converter. [ABSTRACT FROM PUBLISHER]

This paper presents a design, simulation, and evaluation procedure of a variable inductor (VI) for a recently proposed dc-grid LED driver. The design procedure is based on the use of SPICE behavioral modeling to implement the different elements of the equivalent reluctance model of the VI. Thus, the model merges both electrical and magnetic behavior of the VI, including magnetic and geometric features. The basic components of the model are presented in detail, making it possible their use in future designs of VI and other complex magnetic devices. Experimental results from both VI and LED driver prototypes are provided to compare with the simulation results. Obtained outcomes prove that the proposed design and modeling technique is an excellent way to verify theoretical designs and attain further insight about the operation of these complex magnetic devices. [ABSTRACT FROM PUBLISHER]

The effect of ultraviolet-C (UV-C) radiation (doses of 5.4 and 9.46 kJ/m²) on microbiological and lipid and protein oxidation of chicken drumsticks was evaluated at different temperatures of application (5 and 25C). Products were stored 12 days at 5C, showing a reduced number of total aerobic and psychrotrophic bacteria (P < 0.05) along almost all storage period for products treated with UV-C. However, the same effect was not observed for yeasts and molds. Samples treated at 25C presented lower amount of polyunsaturated fatty acid (PUFA) n-6 and n-3 and higher levels of conjugated diene (CD) (P < 0.05) than those treated at 5C. The results suggested the application of UV-C at 5C to provide a lower number of total aerobic and psychrotrophic bacteria with higher levels of PUFA and lower levels of CD. [ABSTRACT FROM AUTHOR]

This paper presents a multifunctional bidirectional converter applied to street lighting and photovoltaic (PV) microgeneration systems. The proposed converter works as an electronic driver supplying a street lighting luminaire based on light emitting diodes (LEDs) at night, from ac single-phase mains with high power factor and reduced harmonic distortion. During daylight hours, the converter injects the produced energy by a PV panel to the grid, working as a grid-tie inverter. The proposed topology is based on the integration of two flyback converters, one for each half-cycle of the grid voltage, avoiding the usual diode bridge rectifier for LED lamps drives, thus providing a bidirectional power flow. A prototype of the proposed electronic stage has been designed, built, and tested, in order to validate the system. Finally, experimental results are presented. In rectifier mode, an efficiency of 86% was achieved, whereas an efficiency of 89% was obtained in inverter mode. [ABSTRACT FROM PUBLISHER]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM PUBLISHER]

This paper proposes an offline single-stage light-emitting diode (LED) driver based on a novel approach to reduce low-frequency ripple in LED arrays supplied from mains, while assuring high input power factor (PF). The proposal employs a series resonant dc–dc converter integrated into a bridgeless boost power factor correction (PFC) stage. The resonant stage works to reduce the low-frequency ripple transmitted from the output of the PFC stage to the LEDs with only small power losses. This solution achieves three main goals: 1) reduction of the bulk capacitance used at the dc bus, allowing for the use of long-life film capacitors; 2) increase in the overall efficiency of the LED driver owing to the low switching and conduction losses in the shared switching network; and 3) assuring high input PF. Experimental results of a driver without electrolytic capacitors for a 100-W street lighting LED luminaire are presented, showing overall efficiency in excess of 92%, input PF greater than 0.97, and line current harmonic content in compliance with the IEC 61000-3-2 standard. [ABSTRACT FROM AUTHOR]

This paper presents a converter structure applied to supply high-power light-emitting diodes (LEDs) from the ac line in a street lighting system, based on the reduced redundant power processing principle. To guarantee high power factor and low harmonic distortion for the input ac current, a buck–boost operating in discontinuous conduction mode is employed as a power factor corrector. The second converter of the structure controls the current on the LED string, but it does not process all the power. This is done by summing the voltages of the first with the second converters. Avoiding the double processing of the power, the efficiency is improved. In addition to that, the capacitance value of the first converter is dramatically reduced by increasing the ripple limits, making possible the use of film capacitors to increase the life span of the system. The power and control designs are shown in detail. A laboratory prototype, with a rated power of 75 W for a rated input voltage of 220 Vrms, was built to show the feasibility of the idea. [ABSTRACT FROM PUBLISHER]

In this paper, a straightforward methodology to modeling high power factor (HPF) ac–dc converters is presented. The proposed methodology is based on the averaging technique directly applied to the converter under modeling. An averaged large-signal equivalent circuit is thus generated, which is useful to perform extremely fast simulations. From the large-signal model, both a steady-state and a small-signal analysis can be carried out to completely model the converter, achieving any desired steady-state characteristic and small-signal transfer function. The presented methodology is very intuitive and allows designers to achieve a natural understanding of the converter behavior. The methodology is illustrated with a HPF buck–boost converter operating in discontinuous conduction mode. Simulation and experimental results are provided to validate the proposed methodology. [ABSTRACT FROM AUTHOR]

A long-life high-power-factor integrated converter able to supply light-emitting diode (LED) lamps in high-pressuresodium lamp retrofitting applications is presented. The proposed converter is the integration of a buck-boost converter with a buck converter, thus providing the necessary high input power factor and voltage transformation ratio to supply the low-voltage LED array from the mains. The analysis of the converter is carried out, and a design procedure is proposed. The design is also performed so that low capacitances are needed at the output of each semi-stage. This allows for the use of long-life film capacitors, thus matching the converter lifetime to that of the LED lamp. A laboratory prototype supplied from 230 Vrms/50 Hz mains used to drive two LED arrays in series with a total output power of 100 W is presented. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM PUBLISHER]

This paper proposes an electronic driver for public lighting systems. The input stage is based on the integration of two flyback converters with different polarities, in order to avoid the use of the input diode bridge rectifying stage. The output stage is a boost converter with an output current control. The proposed circuit is introduced and analyzed, and a design example for a 50-W light-emitting diode lamp is presented. The most relevant simulation and experimental results are also shown, in order to validate the idea. A comparison in terms of efficiency for the input stage is carried out between the proposed topology and the conventional flyback converter, showing an efficiency enhancement in the proposed converter. However, the most important advantage of the proposed converter is outlined in the final part of this paper. This advantage comes from the avoidance of the input diode bridge, thus enabling the bidirectional power flow at the input stage. Therefore, the topology can be used to deliver energy into the power grid. In recent lighting applications, the use of micro renewable generators in lighting points has made the use of special electronics to handle the energy flows in the ballast necessary. The present topology is an alternative to standard bidirectional input stages. [ABSTRACT FROM AUTHOR]

This paper presents the analysis, design, simulation and experimental results of a digital control strategy applied to an electronic ballast to supply a 70-W high-pressure-sodium lamp. The electronic ballast consists of a single-stage converter that integrates a buck converter to provide power factor correction and two flyback converters to supply the lamp, with low frequency square waveform, in order to avoid the acoustic resonance phenomenon occurrence. The proposed digital control strategy is composed of three control loops: voltage loop for lamp ignition and warm-up, an inner current loop for steady state, and a slow outer power loop to maintain the lamp power constant during its useful life. The lamp dynamic model is included to the ac model of the converter, so the effects of its right-half-plane zero are considered to design the digital control system. Fixed-point simulation is presented using Q base number format, where the exact variable values employed in the microcontroller code are used. Experimental results are included to demonstrate the performance of the proposed digital control strategy. [ABSTRACT FROM PUBLISHER]

This paper presents the analysis, design, and experimentation of a closed-loop metal halide (MH) lamp ballast, which supplies the lamp with a low-frequency square waveform. First, a discussion related to the lamp parameter that should be regulated (power or current) is presented, since this issue has not been well addressed in the previous literature. Experiments demonstrated that lamp current can be chosen to be kept constant during lamp life, because it can attenuate the effect of lumen depreciation with lamp ageing, and, on the other hand, the lamp power does not reach overrated values during lamp life. Second, in order to analyze the open-loop characteristic and design a suitable controller for the closed-loop operation, a dynamic model of the lamp-ballast system is developed. Therefore, a phase-lag controller is proposed to minimize the steady-state error and provide a phase margin of about 80^\circ (fully stable system). Experimental results using a flyback-based ballast supplying 35-W MH lamps with 100, 2500, and 5000 burning hours are presented to validate the theoretical analysis. It is demonstrated that the lamp current is kept constant at rated value (0.42 A) within the entire input voltage range. The time response of the complete closed-loop system is about 5 ms. [ABSTRACT FROM PUBLISHER]

The analysis, design, and implementation of a microcontroller-based electronic ballast to supply metal halide (MH) lamps are presented. The proposed topology is based on the integration of the buck and flyback converters, the former providing power factor correction and the latter controlling lamp power. The lamp is supplied by a low-frequency square-waveform current, which is a convenient way to avoid acoustic resonances in high-intensity discharge lamps. Both converters operate in discontinuous conduction mode, thus allowing the use of only one high-frequency switch and simplifying the control. The electronic ballast is digitally controlled by using a low-cost microcontroller PIC16F684. The microcontroller performs all the necessary tasks during starting, warming-up, and steady state, including closed-loop control of lamp current and protections. The closed-loop control takes into account the lamp dynamical impedance. Experimental results for a 35-W MH lamp are presented, and the obtained overall efficiency is 90%. [ABSTRACT FROM AUTHOR]

This paper presents a compact emergency lamp using light-emitting diodes (LEDs). The goal is to develop a compact and low-cost electronic circuit to drive and control the current of LEDs arranged in a single enclosure. The main advantage of the proposed idea is to use the same equipment in the daily activities, supplied by the ac line, and under a mains failure, supplied by a battery. The proposal also aims to achieve energy saving, higher luminous efficacy, and higher useful life when replacing traditional fluorescent-based emergency lighting systems. The use of the E-27 socket provides the advantage of easy installation, with the simple replacement of the lamp without any change in the electrical wiring. Buck and boost converters were employed in order to supply the LEDs by mains and by battery, respectively. However, the converters are designed in order to work without electrolytic capacitors, which have advantages such as reducing size and cost of the circuit, THD reduction, and increasing the useful life of the driver. The battery can be composed of three rechargeable Ni-MH batteries (1.2 V) or a Li-ion battery (3.6 V). The design complies with the Brazilian and international standards for emergency lighting systems and IEC 61000-3-2. The proposed circuit was implemented, and the experimental results were satisfactory. [ABSTRACT FROM AUTHOR]

This paper presents a feedforward fluorescent lamp power regulation method for self-oscillating electronic ballast for different line voltages. The proposed method consists in maintaining the lamp power regulated through the feedforward switching frequency variation using the output resonant filter feature and self-oscillating gate driver circuit. Experimental results demonstrate the feasibility of the proposed solution that allows regulating the lamp power in a wide input voltage range (110 to 220 \Vrms) with an error of up to 12%. [ABSTRACT FROM AUTHOR]

This paper proposes some topologies for developing electronic ballasts, supplying high-intensity discharge lamps fed by a pulsewidth-modulation ac–ac converter, implemented with bidirectional switches. The lamp operates directly from the ac mains; thus, operation with low frequency so as to prevent the occurrence of destructive acoustic resonance is provided. The features of the proposed solution are high efficiency, high power factor, low cost, and the absence of electrolytic capacitors. This paper includes the design of passive elements, the transfer function, and the development of the control strategy. The experimental results qualify the viability of the system feasibility. [ABSTRACT FROM AUTHOR]

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]