Using high frequency current square waveforms to avoid acoustic resonances in low wattage metal halide lamps

Nowadays, one of the main drawbacks in lighting electronics is the appearance of acoustic resonances in HID lamps. In this paper, a new electronic inverter for HID lamps is presented. This inverter provides a high frequency quasi-square current waveform to the lamp. As it is not an ideal waveform, some power harmonics are present in the power frequency spectrum. Nevertheless, a proper design of the inverter can be done in order to keep this power harmonics below the acoustic resonances activation energy threshold level for this kind of lamps. This way, lack of acoustic resonances in low wattage metal halide lamps, with a high fixed frequency, has been obtained. Thus, two features are obtained: lamp stability, and lack of acoustic resonances with a single power stage. A prototype has been built, and successful experiments have been carried out.