| 摘要 |
A closed loop control scheme regulates the lamp intensity of a PL-S lamp at one wavelength by sensing light output by the lamp at another wavelength and controlling lamp power through AC phase modulation. Preferably, the scheme regulates lamp intensity in response to sensed light emitted by the lamp. This scheme provides compensation for lamp and ballast manufacturing variability, temperature effects, line voltage fluctuations, and lamp aging. The controller can set the intensity of a number of banks of lamps, and any lamp can be assigned to any bank. Once set sensing a visible light wavelength and controlling a UV wavelength, the variability of UV light intensity is controlled to within (+/-40 mu W/cm<2> at a 12,000 mu W/cm<2> level (measured substantially at the lamp), representing a 33 % error; and the need to measure the intensity of the process occurs only at regular PMS intervals. The controller monitors and reports lamp failure and near end of lamp life. Soft start circuitry eliminates on/off cycling stresses and cycling lamps on only when needed yields increased lamp useful life. Further, the system reduces typically long warm-up periods experienced in the prior art to a few minutes.
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