| 摘要 |
PURPOSE: To appropriately start a low-pressure discharge lamp under all conditions including a high-temperature restarting condition by providing a ballast circuit additionally comprising a voltage-sensitive bidirectional electronic switch connected in series to an element having a positive temperature coefficient(PTC). CONSTITUTION: A low-frequency input passes through a full-wave bridge rectifier 14 or the like, is converted into a high-frequency alternating current in a high-frequency inverter circuit 30, and then, passes a ballast impedance including a feedback transformer 32 and a resonance ballast inductor 34, thereby setting appropriate starting/operating power value to be applied to a lamp 12. A bidirectional electronic switch 60 is connected in series to a PIC element 64 in an electrothermal preheating circuit 62 in addition to the element 64 and a series capacitor 66, thus forming a low-resistance path for appropriate electrothermal preheating. Since the switch 60 is a bidirectional voltage-sensitive switch such as siduc switch, an electrode can be preheated appropriately even under a high-temperature restarting condition, thereby reducing sputtering of an emitted mixture on the electrode. Moreover, it is possible to improve ballast efficiency and effectiveness of a system. |
