| Summary: | 碩士 === 義守大學 === 電機工程學系碩士班 === 96 === The conventional three-stage electronic ballast for high-intensity-discharge (HID) lamps is composed of a boost pre-regulator to achieve a high power factor, a DC/DC buck converter to regulate lamp power, and a full-bridge inverter for supplying low frequency square-wave sources to the lamps. The drawbacks of the conventional ballast are large size, high losses, and more circuit elements.
Therefore, this thesis presents a novel two-stage low-frequency square-wave driven electronic ballast for HID lamps. The 1st-stage DC/DC converter is a boost converter for input utility-line voltage 85V-rms to 265V-rms and is able to achieve high power factor. The two-stage low-frequency combining with high-frequency driven half-bridge inverter provides low-frequency square-wave sources to the lamp for avoiding acoustic resonance. The thesis also presents a constant power controller which can prevent the lamp from burning or diminishing during start-up periods and supply rated lamp power to the lamp at steady-stage without aging effect. Since the low-frequency combining with high frequency driven half-bridge inverter is designed to be operated at low frequency of 200 Hz, acoustic resonance is not occurre.
A prototype ballast for a 70-W HID lamp is developed and tested under the utility-line voltage(110V-rms, 60Hz). The experimented results show that the measured total efficiency is above 85% and the power factor is above 0.99.
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