| 摘要 |
PROBLEM TO BE SOLVED: To provide an inverter lighting circuit for an outer-electrode fluorescent lamp, which detects lamp breakage to stop an oscillating operation of a switching element, thereby protecting a circuit element. SOLUTION: Voltage is generated by a resistance R1 for current detection of a malfunction detecting circuit DET at the time a lamp current flows, this voltage is rectified by a rectifier circuit RTF to take it out as feedback voltage V1, and in a comparator COMP, reference voltage V0 preset as a value capable of making a sharp distinction between feedback voltage by a lamp current flowing at the time a fluorescent lamp 100 is in a normal state and feed back voltage by a lamp current flowing at the time the lamp has been broken is compared with the actual feedback voltage V1 to turn a switching element Q3 of an inverter circuit INV off when the actual feedback voltage is lower than the reference voltage so as to stop the inverter circuit, thereby preventing the inverter circuit from continuously operating even when the fluorescent lamp has been broken. |
