| 摘要 |
A method and apparatus for controlling the operation of a gas discharge lamp including regulation of power provided to the lamp for maintaining a preselected illumination intensity, automatic lamp shut down for preventing a catastrophic failure of the lamp, and automatic selection of operating frequencies for increasing efficiency and extending useful life of the lamp. An appropriate quality factor Q is achieved by including a low pass filter followed by a high pass filter in the lamp network so as to allow deep dimming of the lamp. Preferably, the arc power delivered to the lamp network is sensed and regulated. By sensing the arc power instead of only the lamp current, the illumination intensity of the lamp is accurately regulated. Further, the lamp ballast is automatically shut down near the end of the lamp's useful life, before operation in partial rectification. Preferably, power to the lamp is shut off based on the arc power entering the lamp network instead of relying only on the voltage of the lamp to avoid unnecessarily shutting down the lamp. The lamp network is automatically operated at an appropriate frequency selected from among a plurality of predetermined frequencies according to the lamp's present mode of operation including: preheating, starting, and continuous operation. Preferably, each frequency is optimized for the particular lamp and for the particular mode of operation.
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