| 摘要 |
POWER SUPPLY Arc discharge lamps driven at frequencies in excess of 20kHz may exhibit the phenomenon of 'acoustic resonance' in which longitudinal and lateral acoustic waves are supported in the arc tube. This is a problem because the acoustic wave may give rise to an instability in the discharge arc, causing it to stretch or gyrate and invariably to extinguish. In some cases damage may be caused to the arc tube. A power supply suitable for an arc discharge lamp (1) comprises a drive circuit (10) arranged to supply voltage to the lamp (1) and control means (20) for causing a characteristic of the voltage to vary, with time, in accordance with a pseudo random sequence in order to reduce, or eliminate, acoustic resonance in the lamp (1). |
