Minimization of acoustic resonances in HID lamps: analysis and comparison of power harmonics content in high frequency non-resonant inverters

Currently, the main drawback in high-intensity discharge lamps supplied by means of high-frequency (HF) electronic ballasts are the so-called acoustic resonances. In this paper, two HF nonresonant inverters for low wattage metal halide (MH) lamps are analyzed, from the point of view of its behavior regarding the acoustic resonances´ phenomenon. Thus, a HF electronic ballast, operating with a lack of acoustic resonances, is proposed. From a dc voltage bus, the inverters provide an ac waveform to the lamp. The power stage operation of the inverters is first analyzed. Then, the characteristics of these waveforms are analyzed, from the point of view of minimizing the acoustic resonances´ appearance. Then, upon these theoretical results, a comparison between inverters is done, selecting the most appropriate for lighting purposes. After that, a built prototype of the chosen inverter topology is presented, and the experimental results are shown. These experiments were carried out on several 70-W MH lamps. Finally, some conclusions are presented.