| 摘要 |
An electronic ballast for driving a plurality of gas discharge lamps in parallel includes a rectifier to convert an AC mains input voltage to a rectified voltage, a filter circuit to convert the rectified voltage to a substantially DC bus voltage, an inverter to convert the DC bus voltage to a high-frequency AC voltage for driving the lamp, and an output stage for coupling the high-frequency AC voltage to the lamps. The ballast also includes a plurality of balancing transformers coupled to the lamps for balancing the currents in the lamps. When one of the parallel lamps is missing or faulty, a substantially large voltage is produced across one or more of the balancing transformers. This large voltage is detected by a missing-lamp detect circuit that provides a control signal to a ballast control circuit. In response to a detected missing-lamp condition, the control circuit stops the ballast from driving the lamps. Optionally, the ballast control circuit can transmit a message regarding the missing-lamp condition via an external communication link.
|
