Ballast For Metal Halide Lamps Research Articles

SINGLE STAGE LOW FREQUENCY ELECTRONIC BALLAST FOR HID LAMPS

The paper presents a single-stage high-power-factor electronic ballast for metal halide lamps. The proposed ballast integrates a buck-boost converter, a buck converter and a full-bridge inverter into a single power conversion circuit. The buck-boost converter served as a power factor corrector (PFC) is designed to operate at discontinuous conduction mode (DCM) to achieve nearly a unity power factor at the input line. By adjusting the duty-ratio of the active switches of the PFC, the lamp power is remained at rated value for universal input voltage ranged from 90 Vrms to 264 Vrms. The four active switches of the full-bridge inverter, an inductor and a capacitor form a bidirectional buck converter which supplies a low frequency square-wave currentfor the lamp at to avoid the lamp from happing acoustic resonance. The circuit operation is analyzed in detail to derive the design equations. A prototype electronic ballast for a 70 W metal halide lamp is built and tested.

Analysis and Design of Self-Oscillating Full-Bridge Electronic Ballast for Metal Halide Lamp at 2.65-MHz Operating Frequency

This paper presents the analysis and design of the self-oscillating full-bridge electronic ballast for the metal halide lamp at 2.65-MHz operating frequency. In order to avoid the acoustic-resonance problem of the metal halide lamp and meet the electromagnetic interference limitation by International Electrotechnical Commission (IEC) regulation, the self-oscillating full-bridge electronic ballast is operated at 2.65-MHz radio frequency (RF). However, the effect caused by the gate-to-source capacitor Cgs of the mosfets on the self-oscillating gate-drive network becomes significant to influence the design of the operating frequency at RF. Therefore, the gate-to-source capacitor Cgs of the mosfets is considered to derive the design equation of the magnetizing inductor for the current transformer in the self-oscillating gate-drive network. Finally, based on the prototype circuit of a 35-W self-oscillating full-bridge electronic ballast with constant-lamp-current control and no-lamp-protection scheme at 2.65-MHz operating frequency, the SIMPLIS simulation and experimental results are used to validate the effect from gate-to-source capacitor Cgs, the proposed design equation, and the design criteria.

A Novel Single-Stage High-Power-Factor Electronic Ballast for Metal-Halide Lamps Free of Acoustic Resonance

This paper proposes a novel single-stage high-power-factor electronic ballast for metal-halide lamps. By integrating two buck-boost converters, a full-bridge inverter and a bidirectional buck converter, a single-stage electronic ballast with symmetrical circuit topology is derived. The circuit component count can be effectively reduced and circuit energy-conversion efficiency is improved. With a tactful control scheme, the proposed electronic ballast can output a low-frequency square-wave voltage to drive metal-halide lamps. The problematic phenomena of acoustic resonance can be eliminated. Both the buck-boost converters serve as power-factor correction (PFC) circuits, which are operated at discontinuous conduction mode (DCM) to obtain a unity power factor at the input line. The operation modes, design equations, and design steps for the circuit parameters are proposed. A prototype circuit designed for a 70-W metal-halide lamp was built and tested to verify the analytical predictions. Satisfactory performances are obtained from the experimental results.

Digital Control Methods of Two-Stage Electronic Ballast for Metal Halide Lamps with a ZVS-QSW Converter

This paper presents a new kind of digital control metal halide lamp electronic ballast. A zero-voltage-switch quasi-square-wave (ZVS-QSW) dual Buck converter is adopted here. In this paper, a digital control method is proposed to achieve ZVS for the converter. This ZVS can be realized during the whole working condition. Single-cycle-peak-current control is proposed to solve the problem of excessive inductor current during a low-frequency reversal transient. Power loop control is also realized and its consistency for different lamps is good. An AVR special microcontroller for a HID ballast is used to raise the control performance, and the low-frequency square-wave control method is adopted to avoid acoustic resonance. A 70W prototype was built in the laboratory. Experimental results show that the electronic ballast works reliably. Furthermore, the efficiency of the ballast can be higher than 92%.

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.

Design and implementation of frequency-modulated electronic ballast for metal-halide lamps

A two-stage, frequency-modulated (FM), high-frequency-driven electronic ballast for metal-halide (MH) lamps is proposed. The presented ballast consists of a power-factor-correction (PFC) converter as the first stage, a half-bridge series-resonant parallel-loaded (HB-SRPL) inverter as the second stage, and a frequency-modulation controller. The advantageous features of the high-frequency-operated ballast are its compact size and reduced weight. With constant-frequency control, the switching frequency of the ballast must be carefully designed within a frequency window that is free from acoustic resonance, and the envelope of the lamp current is large owing to the DC-bus voltage ripple that occurs on the PFC output. However, if the switching frequency of the inverter is operated outside of the stable operation window or if the energy of some eigenfrequency is sufficiently higher, then acoustic resonances will exist. An FM-controlled electronic ballast for MH lamps is proposed. The switching frequency of the HB-SRPL inverter, whose centre frequency is intentionally designed at a frequency at which acoustic resonances occur, is periodically modulated by the voltage ripples of the PFC output. The presented ballast offers a lower envelope of lamp current in order to expand the power spectrum of the lamp and to decrease the energy of the eigenfrequency that supplies the lamp. Owing to its FM operation that allows for an adequately modulated index, no acoustic resonance occurs. The ballast offers cost-effectiveness, a simple control circuit without an external modulation signal, and a low crest factor (<1.45). Design guidelines and experimental results are presented for a 70 W MH lamp ballast that utilises the FM control method with universal-line input voltage.