| 摘要 |
An electronic ballast having a thyristor protective circuit is provided to improve reliability by preventing a malfunction of a protective circuit caused by a voltage drop and a holding current deviation of a rectifier. An electronic ballast having a thyristor protective circuit includes a rectifying and smoothing unit(100), a lamp driving unit(200'), and a lamp unit(300). The rectifying and smoothing unit rectifies and converts an applied AC power into a DC power. The lamp driving unit receives the DC power outputted from the rectifying and smoothing unit, and supplies a driving power to a lamp by switching with a predetermined oscillation frequency in response to a control operation of an internal IC chip. The lamp unit receives the driving power from the lamp driving unit, and is turned on/off. The lamp driving unit has a protective circuit(220') and a feedback circuit unit(210). The protective circuit protects a lamp driving circuit from an over-voltage of a lamp output by switching on the rectifier and shut-downing the IC chip in case that an output of the lamp unit is an abnormal voltage. The feedback circuit unit controls an operation of the IC chip by sensing an error of the lamp and cutting off the driving power applied to the IC chip during the error of the lamp. An anode of the rectifier is directly coupled to a power terminal of the feedback circuit unit without passing through a voltage-drop resistor. |
