| 摘要 |
PURPOSE: A self cutting circuit is provided to achieve in-advance prevention against faults and failures of a ballast and a lamp, by arranging an abnormal signal sensing unit for cutting off power supply to the ballast upon occurrence of faults of the lamp. CONSTITUTION: A self cutting circuit comprises a power supply unit(10), a time delay unit(20), an abnormal signal sensing unit(40), a switching unit(30), a relay driving unit(50), and a ballast driving unit(60). The power supply unit takes, as an input, AC power, converts the AC power into a DC voltage, and supplies the DC voltage. The time delay unit is driven by the DC voltage supplied from the power supply unit, and outputs a high signal after elapse of a predetermined delay time. The abnormal signal sensing unit senses an abnormal signal of a high intensity discharge lamp(70), and outputs a high signal or a low signal. The switching unit processes signals output from the time delay unit and the abnormal signal sensing unit, and outputs a final low signal when the high signal is applied from the abnormal signal sensing unit. The relay driving unit controls supply of driving power to the lamp by switching on/off a relay contact in accordance with the signal output from the switching unit. The ballast driving unit drives a ballast(62) and generates a high pressure pulse for driving the lamp, when the relay contact of the relay driving unit is switched on.
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