| 摘要 |
1533646 Starting discharge lamps PHILIPS ELECTRONIC & ASSOCIATED INDUSTRIES Ltd 18 Nov 1976 [21 Nov 1975] 48092/76 Heading H2H An arrangement for starting a discharge lamp 4 comprises a series circuit including a capacitor 7, a positive temperature coefficient resistor 8 and a bidirectional thyristor 10. When a mains A.C. supply is connected to the lamp, which may be a low-pressure mercury vapour lamp, a capacitor 14 is charged until a disc 16 breaks down thereby triggering the thyristor 10. Current flows through a circuit including the capacitor 7 and a ballast inductance 6 which supply a high voltage to the electrodes 3, 5 of the lamp. The lamp ignites and the voltage across it falls to a value which is too low to cause further breakdown of the diac 16. If the lamp fails to ignite the current through the resistor 8 and the thyristor 10 heats the resistor thereby greatly increasing its resistance so that the current is reduced until it is insufficient to maintain the thyristor 10 conductive. The lamp may have pre-heatable electrodes.
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