Influence of driving current waveforms on lighting characteristics of HID lamp

摘要

Short-arc-type metal halide lamps have some better features of a higher efficacy and color rendering property among many kinds of HID lamps (High Intensity Discharge Lamps), and they are widely used as light sources for liquid crystal projectors of small size. However; this metal halide lamp has a problem that optical flickers occur due to the irregular movement of arc position. Previously; a method of suppressing those optical flickers has been proposed. This is to suppress the arc-position movement by superposing a pulse on the rectangular waveform of lamp current just before its polarity changes. This paper discusses the influence of superposed waveforms on the lighting state. In the experiment, many kinds of waveforms were superposed on the rectangular current, and the occurrence of optical flickers was checked. As a result, the effectiveness of some waveforms for the optical-flicker suppression was confirmed.