J. Ribas

Single-stage constant-wattage high-power-factor electronic ballast with dimming capability

A novel single-stage high-power-factor electronic ballast is presented in this paper. The ballast is obtained from the integration of a buck-boost converter and a half-bridge LC resonant inverter. The ballast features lamp power regulation against line voltage fluctuations together with high power factor and dimming capability. The steady-state analysis of the ballast is performed and a low-frequency model of the input stage is derived. A design example, including closed-loop circuitry, is also presented. Finally some experimental results from a lab prototype are shown.

Analysis, design and experimentation of a high voltage power supply for ozone generation based on the current-fed parallel-resonant push-pull inverter

The use of supply frequencies above 50-60 Hz allows for an increase in the power density applied to the ozonizer electrode surface and an increase in ozone production for a given surface area, while decreasing the necessary peak voltage. Parallel-resonant converters are well suited for supplying the high capacitive load of ozonizers. Therefore, in this paper the current-fed parallel-resonant push-pull inverter is proposed as a good option to implement high-voltage high-frequency power supplies for ozone generators. The proposed converter is analyzed and some important characteristics are obtained. The design and implementation of the complete power supply are also shown. The UC3872 integrated circuit is proposed in order to operate the converter at resonance, allowing us to maintain a good response disregarding the changes in electric parameters of the transformer-ozonizer pair. Experimental results for a 50-W prototype are also provided.

Evaluation of a low-cost permanent emergency lighting system based on high-efficiency LEDs

Nowadays, Permanent Emergency Lighting Systems (PELSs) are widely used in many applications, including emergency exit indication and lighting in critical or strategic points. Limitation in operation hours in classical lamps (10 000-20 000 h for fluorescent lamps) implies short lamp replacement times and, therefore, high maintenance costs. This paper shows an alternative solution based on high-efficiency LEDs. The long operation life (above 100 000 h) of high-efficiency LEDs with a very simple electronics circuitry implies an interesting solution for these types of applications. A 30-lm and 1-h PELS has been built and tested. A low-cost power supply has been built and used as a battery charger and LED driver.

Low cost electronic ballast for a 36-W fluorescent lamp based on a current-mode-controlled boost inverter for a 120-V DC bus power distribution

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.

High Voltage Power Supply for Ozone Generation Based on Piezoelectric Transformer

Even though nowadays piezoelectric transformers (PT) 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 closed loop by measuring the phase between the PTs 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.

High Frequency Testing and Modeling of Silent Discharge Ozone Generators

This paper deals with high frequency modeling of silent discharge ozone generators (OGs). The electrical characteristics of two simple silent discharge OGs operated at low and high frequency are analyzed and compared. An equivalent electric model is proposed for the operation of the OG at high frequency. This model can be used to optimize the electronic power converter used to supply silent discharge OGs at high frequency. Experimental results measured in the laboratory for two particular OGs are presented to validate the proposed model.

Electronic driver without electrolytic capacitor for dimming High Brightness LEDs

This paper presents a full ballast for driving an assembly of High Brightness LEDs, based on a new dc to dc converter. The converter provides a constant current waveform to the load parting from a DC bus voltage. The converter, operating with a peak current control, keeps the current through the LEDs constant independently of the bus voltage. This is carried out internally by self-adjusting the switching frequency of the converter. Thus, the requirements of the capacitance of the bus capacitor are greatly diminished, allowing the avoidance of electrolytic technology. Also, low frequency PWM dimming can be carried out easily. The present work shows the design procedure and the experimental results obtained after building a prototype of a full ballast for HB LEDs.

Analysis and design of a novel single-stage high-power-factor electronic ballast based on integrated buck half-bridge resonant inverter

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.

Arc stabilization in low-frequency square-wave electronic ballast for metal halide lamps

Discharge lamps present a negative dynamic characteristic that makes necessary using 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 stage feeding the square wave inverter. Therefore, the design of the input converter must be made taking into account the lamp dynamic characteristic. This paper presents a new procedure for obtaining the small-signal dynamic characteristic of metal halide lamps is proposed. Using the proposed methodology the small-signal characteristic of a 70 W 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.

Analysis and experimental results of a single-stage high-power-factor electronic ballast based on flyback converter

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.