| 摘要 |
An electronic ballast having particular application for driving small diameter fluorescent tubes or lamps (such as the T2, T4 and T5 sizes). The electronic ballast has a shutdown circuit (D13 and TR3) by which to remove power to an oscillator (TR1 and TR2) when the tube or lamp (26 and 28) is close to the end of its useful life or when an abnormal condition occurs such that a rise in operating voltage is detected. The shutdown circuit (D13 and TR3) detects the rise in the operating voltage of the tube or lamp (26 and 28) and energizes a relay (40) through the conduction path of a photoresponsive transistor (TR) that is rendered conducting by a light emitting diode (48). The relay (40) directs power away from the oscillator (TR1 and TR2) and towards the control electrode of the photoresponsive transistor (TR) to hold said transistor on and thereby disable the ballast. |
