| 摘要 |
PROBLEM TO BE SOLVED: To protect even the particularly slight disconnection without overlooking it by providing a detecting circuit regarding it as no-load time when the electrode filaments are disconnected even if a fluorescent lamp is connected needless to say that the fluorescent lamp is not connected. SOLUTION: Half bridge-shaped inverter circuits 2, 3, 9, 10 are provided to convert voltage of a DC power source 40 into high frequency voltage. Fluorescent lamp lighting circuits 4, 5, 6 are provided. A control circuit 1 is provided to control the inverter circuits. An abnormal voltage detecting circuit is provided to monitor tube voltage of a fluorescent 4 belonging to the fluorescent lamp lighting circuits. A no-load detecting circuit is provided to detect the existence of the connection of the fluorescent lamp 4. Output of the inverter circuits is at least restricted at abnormal voltage detecting time and no-load time. The no-load detecting circuit is a detecting circuit regarding it as no-load time when the electrode filaments 4a, 4b are disconnected even if the fluorescent lamp 4 is connected needless to say that the fluorescent lamp 4 is not connected. |
