| 摘要 |
PURPOSE:To provide a lamp lighting device which close not cause faulty operation even when a fluorescent lamp is started, and also can suspend the operation of a lighting circuit without delay when an abnormal condition takes place. CONSTITUTION:An inverter circuit 1 allows a fluorescent lamp FL to be fully or dimly lighted in accordance with the output of a control circuit 2. When the voltage of the fluorescent lamp FL is stepped up because of its life end, lamp voltage is detected by a lamp voltage detection circuit 3, and since a transistor Q is turned on, it is then detected whether or not the aforesaid voltage is higher than the voltage of resistors R4 and R5 which is to be reference voltage. When it is higher than the reference voltage, the excitation of the inver circuit 1 is suspended by the control circuit 2. Since a capacitor C3 is not charged during the specified period of time before the fluorescent lamp FL is lighted, a Zener diode ZD2 will never conduct electricity reversely. Reference voltage is made higher than normal by using the resistor R5 only with the transistor Q left in an 'off' condition. |
