| 摘要 |
An energy conserving lighting system is provided wherein a plurality of fluorescent lamps are powered by a poorly regulated voltage source power supply which provides a decreasing supply voltage with increasing arc current so as to generally match the volt-ampere characteristics of the lamps. A transistor ballast and control circuit connected in the arc current path controls the arc current, and hence the light output, in accordance with the total ambient light, i.e., the light produced by the lamps together with whatever further light is produced by other sources such as daylight. In another embodiment, a transistor ballast is utilized in combination with an inductive ballast. The transistor ballast provides current control over a wide dynamic range up to a design current maximum at which maximum the transistor is saturated and the inductive ballast takes over the current limiting function. An operational amplifier is preferably connected in the base biassing circuit of the control transistor of the transistor ballast. In an embodiment wherein two sets of lamps with separate inductive ballasts are provided, the arc currents for the two ballasts are scaled or matched to provide the desired light output.
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