| 摘要 |
A driver (10) produces a current to generate traveling waves of voltage for low levels of illumination and an arc voltage for high levels of illumination through a gas discharge lamp (50). At the low illumination levels the traveling waves of voltage are produced in a manner so as to increase the current in the lamp at a controlled rate so that the increase in current can be stopped by an optical or ionization feedback loop (80) when the lamp reaches the glow discharge region, after the Townsend discharge region (B) and before the arc discharge region (D). Without careful control of the rate of the current increase, the desired current level can easily be overshot or undershot. Also, the feedback is critical given the varying nature of the impedance of gas discharge lamps. The process is repeated at selected intervals to produce a desired average level of illumination. The nature of the traveling waves assists the direction of ion acceleration toward the walls of the lamp (50), allowing the lamp to be brought to the glow discharge region (C) without damage to the cathode filaments (250a, 250b).
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