| 摘要 |
PURPOSE:To accurately the life of a discharge lamp, by detecting the positive and negative asymmetry of both terminal voltages of the electrode filament of the discharge lamp during lighting. CONSTITUTION:In constitution consisting of a power source AC, a lighting circuit B, a fluorescent lamp FL and a starter S, a circuit J for detecting the positive and negative assymmetry of filament body terminal voltages Vf is connected to both terminals of the filament F of the fluorescent lamp FL and a display circuit Q is further connected. Filament body terminal voltages Vf are becomes high only in negative voltage with the elapse of lighting time and positive voltage is almost constant. In the detection circuit J, an integrator circuit is constituted of a resistor R1 and a capacitor C to detect the difference of DC components of filament both terminal voltages Vf and connected to the display circuit Q constituted of a resistor R2 and a light emitting diode D. By this mechanism, accurate lamp life can be judged.
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