| 摘要 |
PURPOSE: To adjust lamp power in a wide range, regardless of the kind of a discharge lamp by causing a control signal controlling a frequency of conducting and nonconducting of switching elements depending on the signal of the comparatively quick change measure of the consumed electric power by the discharge lamp. CONSTITUTION: In a regular operation state, switching elements T1, T2 are alternately brought into conduction at a frequency (f) by a drive circuit E. As a result, the square-wave voltage of the frequency (f) exists across both ends of a load branch B, and a current whose polarity changes at the frequency (f) flows in the load branch B. The frequency (f) is nearly equal to the frequency of a control signal. The control signal frequency depends on a voltage VREF, which is a measure with respect to a required lamp electric power and an actual lamp electric power. Owing to the action of a voltage across both ends of a resistance RS, the control signal depends on the comparatively quick change of the lamp electric power, so that the required lamp electric power can be obtained without generating oscillation, regardless of the kind of discharge lamps used. |
