| 摘要 |
<p>BALLAST CIRCUIT FOR ACCURATELY REGULATING HID LAMP WATTAGE Circuit for regulating the wattage drawn by a high-intensity-discharge (HID) lamp and for limiting the line current drawn by the lamp during starting to less than the line current drawn during normal lamp operation. The circuit includes a lamp current controlling means which has two operating modes, a first of which passes a less-than-nominal current to the lamp and a second of which passes a greaterthan-nominal current to the lamp, with the ratio of the current of the second mode to the current of the first mode being less than 2:1. The lamp voltage is sensed and the line voltage also is sensed and these parameters are converted into separate current signals which are fed into a ramp capacitor to control the charging rate thereof. When the ramp capacitor achieves a predetermined level of charge during each half cycle of energizing potential, an AC switch is gated to shift the current controlling means from the first mode to the second mode. During lamp starting when the voltage drop thereacross is relatively low, the current controlling means remains in the first mode for at least the substantial portion of each half cycle of energizing potential, and after the lamp is normally operating, the ramp capacitor control, coupled with the low ratio of relative currents passed by the current controlling means, provides for an accurate control of lamp wattage and excellent overall performance. This application is a continuation-in-part of applycation S.N. 776,804 filed March 11, 1977 by Joseph C. Engel and Robert T. Elms, the present applicants, and owned by the present assignee.</p> |
