| 摘要 |
PURPOSE:To protect circuit during no-load by running lamp current of a fluorescent lamp and preheating current in a first coil of a three-coiled transformer, so as to induce voltage only by the lamp current of the first coil in a third coil, and by defining the voltage as the feedback voltage by which oscillating of a timer IC is continued. CONSTITUTION:When the life of a fluorescent lamp 1 is running out and the lamp is in a no-emission state, preheating current Ib alone runs in a first coil N1 of a three-coiled transformer 16, and the voltage of a third coil N3 induced by the current is cancelled by a second coil, whereby voltage is not induced in the third coil N3. Voltage fed back to a timer IC9 runs out, and the oscillation of the timer IC9 is stopped, while the switching operation of an oscillating transistor 10 is stopped, whereby the possibility of the oscillating transistor 10 being abnormally oscillated and heated thereby is eliminated, and the circuit protection during no-emission can be assured. |
