M. Rico

A single stage fluorescent lamp ballast with high power factor

The steady state operation modes and the commutation zones of a single stage, high power factor ballast are studied. The design criteria to allow the ballast to operate at the optimum soft switching conditions are given. A control circuit is also proposed. High efficiency is achieved by soft switching. Experimental results verify the theoretical study.

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 power 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.

A microcontroller-based emergency ballast for fluorescent lamps

This paper presents a new emergency ballast for fluorescent lamps. The fundamental block is the microcontroller-based control circuit, which performs the supervision and control function. High-frequency electronics techniques are proposed for the high power factor battery charger and the lamp driver, which provides high luminous efficacy. In this way, size and weight have been minimized for the whole system. With the introduction of the microcontroller, the system has the capability of testing itself, checking its functional state, and displaying internal faults. Thus, the reliability of the system is improved and, concurrently, maintenance cost is decreased.

Analysis, design, and optimization of the LCC resonant inverter as a high-intensity discharge lamp ballast

A complete study of the clamped-mode (CM) series-parallel (LCC) resonant inverter together with some of the control-to-output characteristics are presented in this paper. Also, a new control method for the CM LCC resonant inverter is introduced. With this method, the inverter is forced to operate with optimum commutations and without handling reactive energy, thus minimizing both switching and conduction losses. The corresponding design procedure is illustrated with a design example. Finally, some experimental results obtained from a prototype at the laboratory are also shown to validate the analysis and evaluate the proposed control method.

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.

A novel low-loss clamped-mode LCC resonant inverter for HID lamp supply

A novel clamped-mode LCC resonant inverter with very low losses is presented in this paper. Switching and conduction losses are minimized forcing the inverter to operate with optimum commutations and without handling reactive energy. Output power is controlled via switching frequency and the clamped interval is self-adjusted by the resonant current to obtain optimum commutation. In this way, a very simple circuit can be used to control the inverter and the efficiency achieved is very high.<<ETX>>

An estimator of luminous flux for enhanced control of high brightness LEDs

Usually, PWM operation is selected to drive High Brightness LEDs, because the dimming behavior is more linear than in DC operation. Nevertheless, to obtain an enhanced operation of the device (full output light control), the luminous flux should be measured. This paper proposes a control method based on an estimator of the luminous flux emitted by the LED. Firstly, the LEDs are characterized. Based on these characterization, an estimator of the flux emitted by the LED is defined. The estimator provides this flux value from only two temperature values (the case temperature and the ambient temperature). The estimator is defined and validated in steady state as well as in the transient stage. The flux estimator is then validated with actual measurements. Once the estimator is defined and validated, the electronic driver to supply the LEDs as well as the digital control scheme are presented. Finally, a built prototype is presented, and the experimental results are shown. Conclusions of this work show that with the presented estimator, both the steady state and the transient luminous flux 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 a DC operation of the LEDs.

A new topology for high voltage, high frequency transformers

When a DC high voltage needs to be obtained from low voltage inputs (mains voltage), the necessary power converter needs a high value for its transformation ratio; consequently, a large number of turns is often necessary for secondary windings and some parasitics appear (large leakage inductance and large capacitance). Thus, it is usual to design a resonant converter to include both inductance and capacitance in the power topology. However, as the parasitics are used to obtain the resonance, their value (and their spreads) are critical. The paper proposes several criteria in order to establish an adequate method for constructing the transformer, and a new topology for transformers and a model for parasitic capacitances are also presented taking into account high voltage and high frequency problems and limitations of materials.<<ETX>>

Arc Dynamic Stabilization in Low-Frequency Square-Wave Electronic Ballast for Metal Halide Lamps

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.

Small signal dynamic characterization of HID lamps

In the literature, several low-signal dynamic models for fluorescent lamps have been presented. These models can be used to analyze the lamp-ballast interaction in high frequency electronic ballasts. However, the small signal characteristics of HID lamps differ from those of fluorescent lamps, so the models described in previous literature cannot be applied to the analysis of HID lamp ballasts. In the present paper the small-signal characteristics of a mercury vapor lamp and a high pressure sodium lamp are obtained and compared to the typical characteristics of fluorescent lamps. The main differences between HID and fluorescent lamp small-signal characteristics are remarked upon. The key points for the stability analysis of the lamp-ballast system are also addressed in this paper. Using the multi-frequency averaging technique the interaction between a high pressure sodium lamp and a resonant inverter is analyzed and verified using a laboratory prototype.