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%.

A Single-Stage High-Power-Factor Electronic Ballast Based on Integrated Buck Flyback Converter to Supply Metal Halide Lamps

The increasing speed of modern power electronics opens a way to study the stability of high-intensity-discharge lamps at very-high-frequency operation. In this paper, a lamp stability study based on a simplified theory on acoustic resonance frequency distribution in a small-wattage metal-halide (MH) lamp is presented. The frequency characteristic of a low-wattage MH lamp has been analyzed. Up to 700 kHz, extensive experiments using resonant-type electronic ballast have been conducted on 35-W MH lamps to investigate different control methods for avoiding acoustic resonance. The results indicate that a randomized switching scheme cannot always eliminate are instabilities caused by acoustic resonances in small-wattage MH lamps. The stability frequency regions should be identified. A stable arc can be obtained when the lamp is operated above the highest acoustic resonance frequency.

Stability study and control methods for small-wattage high-intensity-discharge (HID) lamps

In this paper, a study about acoustic resonance (AR) in low-wattage metal halide lamps is presented. The lamps are supplied with a typical low frequency square waveform on which a high frequency sinusoidal ripple is superposed. The goal is to emulate the same waveforms generated by a low frequency electronic ballast. In this way, the ARs that appear in the lamp can be characterized against ripple amplitude and frequency. Different lamp's manufacturers and burning hours are used. The obtained results are intended to be employed in further reliable designs of low-frequency square-waveform electronic ballasts. An example of application of the accumulated AR signatures in this type of electronic ballasts is carried out, and a standard proposal is presented

Acoustic Resonance Characterization of Low-Wattage Metal-Halide Lamps Under Low-Frequency Square-Waveform Operation

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

Acoustic-Resonance Characterization of Low-Wattage Metal–Halide Lamps

This paper presents a novel single-stage electronic ballast with high power factor. 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 current in the main switch, which handles only the flyback or buck current, depending on the operation mode. In order to supply the lamp with a low frequency square-wave current, to avoid acoustic resonances, the flyback has two secondary windings that operate complementary at low frequency. Results of acoustic resonances excited by the high-frequency ripple in the square waveform applied to the lamp are presented, in order to design the circuit. 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 0.956, a total harmonic distortion of 30%, complying with IEC 61000-3-2, and an efficiency of 90%.

https://ieeexplore.ieee.org/iel5/10182/32506/01518510.pdf

A novel low-cost electronic ballast to supply metal halide lamps

A novel type of solid-state ballast, which operates in the megahertz-range frequency, is presented in this paper. A circuit composed of a voltage-fed half-bridge inverter, a distributed constant line, and a parallel LC resonant circuit has been developed for this purpose. The high-intensity discharge (HID) lamp is connected to the output terminal of the inverter through the distributed constant line. Here, since the length of the line is adjusted to 1/4 of the propagation wavelength /spl lambda/, the output voltage of the voltage-fed inverter can be converted to a current source on the load side. Based on the experiment results, the ballast appears to be able to supply not only high voltage, but also constant current for ignition of the HID lamp. The experimental results from a prototype system are used to verify the theoretical procedure.

H. Takagi

Papers

Megahertz operation of voltage-fed inverter for HID lamps using distributed constant line