| 摘要 |
<p>An electronic ballast for a gas discharge lamp includes an AC to DC converter for changing alternating current at power line voltage to direct current and an inverter powered by the converter and having a series resonant output coupled to the lamp. The inverter includes an AC switch (10) having a diode bridge (16, 17, 18, 19) defining an AC diagonal and a DC diagonal. A transistor (21) is connected across the DC diagonal. The primary winding of a filament transformer is connected across the AC diagonal of the bridge in series with the secondary of another transformer (14). The primary of the other transformer (14) is the inductor in the series resonant output. The transistor (21) conducts while the lamp is starting and stops conducting after the lamp is started, thereby cutting off the filaments from a source of power and reducing the power consumed by the ballast during normal operation. A resistor (22) in series with the transistor (21) is used to detect filament resistance and provide an indication of lamp type.</p> |
