F.E. Bisogno

A practical comparison among high-power-factor electronic ballasts with similar ideas

This paper provides a comparative analysis among four electronic ballast topologies with high power factor, employing the same switch for inverter and power factor correction stage. The analyses done are based on experimental results. A commercial electromagnetic ballast (EMB) is tested to provide a comparison with implemented electronic ballasts. The features of each topology are shown through the discussion of their advantages and disadvantages. The electronic ballasts are made for two 40-W fluorescent lamps at 50-kHz switching frequency and for a 110-V/sub rms/ 60-Hz utility line.

Self-oscillating dimmable electronic ballast

This paper presents a simple alternative for an electronic ballast operating in self-sustained oscillating mode with dimming capability for fluorescent lamps. A simple modification in one of the gate drivers side circuit allows the lamp to dim without compromising the simplicity, reliability, and low cost which characterize the self-oscillating electronic ballast (SOEB). A qualitative analysis is presented to explain the behavior of the proposed self-oscillating electronic ballast with dimming feature. In addition, the stability and the key equations for the design are derived using the extended Nyquist criterion and describing function method. Experimental results from two 40-W electronic ballasts are presented to demonstrate the performance and to validate the analysis carried out.

A Design Methodology for a Self-Oscillating Electronic Ballast

This paper presents a design methodology and analysis of electronic ballast employing the self-oscillating-command circuit. The self-oscillating electronic ballast is represented as a relay control system in order to determine its parameters using the describing-function method and an extended Nyquist stability criterion. Simulation and experimental results of the electronic ballast supplying a 40-W fluorescent lamp are presented in order to confirm the feasibility of the performed design methodology.

Resonant filter applications in electronic ballast

In this paper an analysis is presented of the resonant filter used in an electronic ballast through the phase angle from the input resonant filter current to the input resonant filter voltage. The proposed analysis allows evaluation of the resonant filter characteristics. The main characteristics that are analyzed are: lamp starting, soft commutation, DC current in the lamp, resonant filter influence in the converters and lamp pre-heating. This work allows a choice of the best filter to employ in an electronic ballast for fluorescent lamps.

Fluorescent lamp model based on the equivalent resistance variation

A circuit model simulating the electrical characteristics of a fluorescent lamp operating at high frequency is proposed. The model is based on exponential approximation that represents the equivalent resistance variation as function of power, constructed by experimental results for several power levels. Simulations and experimental results are presented to verify the feasibility of the model and, moreover, an electronic ballast example using the proposed model is presented to further demonstrate its applications.

Effects of the Junction Temperature on the Dynamic Resistance of White LEDs

This paper deals with the thermal characteristics of the I-V curve of GaN-based white LEDs, focused on the variations of the dynamic resistance. The final goal of this study is to improve the static and dynamic operation of the LED driver within a wide range of temperature. Four LEDs from different manufacturers were chosen for this study. The first part of the paper shows the thermal characterization of the forward voltage at a given injected current. After that, the experimental data are fitted in order to calculate the junction temperature accurately. Then, a small-signal analysis where the LEDs are supplied with dc current and an ac perturbation superimposed at the operation point under variable junction temperature is covered. This analysis allows the dynamic resistance to be experimentally determined for a wide junction temperature range. Furthermore, the experimental data have been fitted in order to establish the relationship between junction temperature and dynamic resistance variation, so the dynamic resistance can be determined for a given operation point. Finally, an illustrative example is presented as a case study in order to analyze the implications of the dynamic resistance on the output current ripple and on the closed-loop operation of an LED driver. The experimental results confirm that the junction temperature shift induces a variation in the dynamic resistance, which might have a significant effect on the output current ripple and closed-loop performance in certain LED fixtures.

Self-oscillating electronic ballast design based on the point of view of control system

This paper presents a design methodology, analysis, and practical considerations of self-oscillating drive circuit for electronic ballasts by considering the self-oscillating electronic ballast as a relay control system. The first section of the paper analyzes the design of resonant elements, the nonlinearity present in the circuit and consideration to apply the methodology proposed. The second section of the paper shows the design of self-oscillating electronic ballast using control tools such as: describing function, extended Nyquist criterion and block diagrams that allows an expression for designing the self-oscillating electronic ballast to be found.

Simple valley-fill self-oscillating electronic ballast with low crest factor using pulse-frequency modulation

This paper presents an alternative to achieve fluorescent lamp current low crest factor, using the valley-fill filter as a passive power-factor-correction method. Pulse frequency modulation is used to reduce lamp current high crest factor. Self-oscillating electronic ballast is employed in order to avoid complex circuitry. The partial smoothing valley-fill DC-link bus voltage is used to control the switching frequency. Crest factor correction is achieved through a low power bipolar transistor, which connects a low power passive circuit parallel within the self-oscillating gate-driver circuit. The switching frequency changes in order to keep the lamp current crest factor lower than 1.7 and a modified valley-fill filter is used to meet IEC61000-3-2 requirements. Simulations and experimental results are presented to demonstrate the simplicity, and feasibility of the proposed system.

A design method for electronic ballast for fluorescent lamps

This paper presents a new design methodology, analysis, and practical considerations about series parallel resonant filter, LCC, for electronic ballasts employing the self-oscillating driver circuit. Designs equations and graphic methods are presented, obtained by analysis of Fourier series, Tsypkins Locus and stability tests. The lamp high frequency supply is given by the half-bridge converter, and the verification of this approach is guaranteed by simulation and experimental results.

A unity power factor electronic ballast for fluorescent lighting

This paper describes a high power factor electronic ballast for fluorescent lamps. The converter offers a high power factor and high-frequency supply to the lamp. In spite of its simplicity an excellent performance concerning load and supply is achieved, ensuring a sinusoidal and in-phase supply current. High power factor is achieved by using a flyback converter operating in discontinuous-conduction mode. Operating principle, design equations, control characteristics, component stress, and efficiency are presented. Experimental results have been obtained for one 40 W fluorescent lamp operating at 50 kHz switching frequency and 220 V line voltage.