| 摘要 |
PURPOSE:To enable the detection of a no-load condition by charging a capacitor via a no-load detection circuit during a no-load. CONSTITUTION:The secondary windings n2 to n4 of an inductance element L are connected to filaments f1 to f4 via respective capacitors C3 to C5. When an electric discharge lamps l1 and l2 turn into a no-load condition, a capacitor C1 is charged up to the voltage level of a direct current power supply E via resistors R1 and R2. In this case, a direct current interruption element is provided between the preheating windings n2 to n4 and the filaments f1 to f4 in order to interrupt discharge current of direct current characteristics from C1. According to the aforesaid construction, the charging voltage of the capacitor C1 rises at the time of no-load and there appears a voltage drop in a no-load detection circuit 1, thereby enabling the detection of a no-load condition. |
