| 摘要 |
PROBLEM TO BE SOLVED: To provide a dimmed lighting device which can be lighted up certainly in a low temp. condition through lessening of the flash at lighting, by transferring the output frequency of a high frequency power supply in the starting period of lamp from a frequency apart from the resonance frequency of an LC resonator circuit gradually into the resonance frequency. SOLUTION: The voltage of a discharge lamp 1 is sensed by a voltage sensing circuit 6 and fed to a control part 3, and the output therefrom is fed to a high frequency power supply 2. When the power is put on for a timer A7, the set time ta is counted, and meantime a frequency sweeping circuit A8 makes sweeping from the frequency f1 to f2. The frequency f1 is set apart from the resonance frequency fo of a resonator circuit consisting of a coil 4 and capacitor 5, while f2 is set in the neighborhood of fo. When the discharge lamp 1 makes discharge, momentary transition is made into the dimming frequency f3. With the start of the discharge, the impedance of the lamp 1 lowers, and the impression voltage sinks rapidly. As transition is made momentarily into the set dimming light flux from a large light flux of the lamp 1 when it starts discharging, a human eye will not feel the change significantly. |
