1983 Volume 67 Issue 2 Pages 55-61
High frequency characteristics of operating HID lamps were presented over a frequency range of 60 Hz to 20, 000 Hz. But in order to develope a new solid state ballast, it is necessary to investigate the characteristics over 20, 000 Hz.
While operating HID lamps on high frequency power, the arc instability is observed. Arc flutters, snakes and sometimes extinguishes. This is called an acoustic resonance. This phenomenon occurs when the sound wave inside the arc tube specified by the tube shape and gases is resonant with the imposed high frequency power.
Metal-halide lamp is difficult to operate stably on high frequency power because the wide unstable frequency range exists between 20 kHz and 50 kHz.
The resonant frequency ranges of high pressure sodium lamp are narrow and exhibited at intervals. Therefore, HPS lamp is easy for the stable high frequency operation at the suitable selected frequency.
The stable frequency range of mercury lamp is relatively narrow and it can be easily shif ted with the lamp tolerance and the lamp watt variation for the same rated lamp. And so the high frequency operation is difficult for mercury lamp.
To eliminate the acoustic resonance, four ways of stable operation are presented. The first is to operate HID lamp at a frequency above all the acoustic resonancl frequencies. Secondly, square wave operation is good way for the stable operation The third is to operate with suitable frequency modulated waves. The last is to operate sinuous high frequency wave superposed with the 3rd harmonic frequency.
The third and the last are better for designing ballast. That is because these ways of operation would be realized by the practical circuit (approxmately 20-50 kHz) as the fluorescent lamp is operated.
The HID lamp solid state ballast should be developed by the way described in this paper.