Series Igniters Effects in Metal Halide Lamps Operation With High Frequency Ballasts: Study and Minimization

The use of high frequency (HF) square waveforms is a possible metal halide (MH) lamps supply method which can be implemented by means of non-resonant electronic inverters. This strategy can successfully avoid acoustic resonances appearance in such kind of lamps (theoretically, in a perfect square waveform, no power modulation is found). The main drawbacks of this kind of inverters are the electromagnetic interference emissions and the parasitic effects of the series igniters. This effect can spoil the square waveforms on the lamp, hence injecting HF harmonics in the lamp supply power spectrum, eventually leading to acoustic resonances appearance. In this paper, this effect is studied, in order to limit the values of the parasitic elements of the series igniter compatible with a proper operation of the HF inverter. Once these values are estimated, such an igniter has been built and tested, thus obtaining a practical HF (100 kHz) square waveform inverter with series igniter for 35-W MH lamps