| 摘要 |
<p>An operating circuit by which the damage to the electrodes of an HID lamp is reduced when the lamp is ignited, the lamp power is controlled more minutely than the clock frequency of the computer, and the heat generated from the lamp power control circuit is suppressed. The operating circuit comprises a control unit (C) provided with ignition start control means for suppressing the lamp power below the rated working power after the ignition of the discharge of the HID lamp (1), maintaining the lamp power at the ignition start power with which the HID lamp can maintain its discharge, and increasing the lamp power to the rated working power after the internal vapor pressure of the HID lamp (1) reaches a predetermined value, lamp power control means for varying the pulse width of the power control pulse signal by one clock pulse so that the time average of the lamp power varying depending on the pulse width of the power control pulse signal during the self-maintaining discharge may agree with the predetermined target lamp power, and input voltage control means for varying the direct current smoothing voltage inputted to a lamp power control circuit (8) depending on its output voltage.</p> |
