| 摘要 |
PURPOSE: To provide a luminance lowering circuit which is capable of easily controlling the luminance of a fluorescent lamp and preventing an overcorrect in a no-load state, caused by the contact failure of the fluorescent lamp. CONSTITUTION: In a luminance lowering circuit, having a magnetic force oscillating means having a transformer 18 with three windings, a second winding or the transformer 18 is connected to a DC power source, and a third winding is connected to a fluorescent lamp 21. The second winding is also connected to an oscillating circuit, and this oscillating circuit has a first resistor 12, transistors 16, 17 and first winding. This circuit comprises a variable resistor 14 to be connected in series with the first resistor 12, and the variable resistor 14 includes a movable arm to be connected to the first winding, the operating frequency of the fluorescent is controlled, and as a result the luminance is controlled. |
