| 摘要 |
PROBLEM TO BE SOLVED: To impress an appropriate voltage to a discharge lamp even at the time of soft-starting. SOLUTION: Fluorescent lamps FL1, FL2 are preheated for about one second after power source feed in a condition that an output of an inverter circuit 15 is slightly low, to be soft-started. A power source voltage is monitored based on a transistor Q14, an output voltage of the inverter circuit 15 is made constant by feedfoward control, and a gate voltage of an electric field-effect transistor Q2 keeps constant an output of the inverter circuit 15 coping with a wide range of the power source voltage to preheat the fluorescent lamps FL1, FL2. Feedback control is conducted by voltages corresponding to the lamps FL1, FL2 induced in a sub-winding Tr2. The fluorescent lamps FL1, FL2 are prevented from being blackened in an early stage because of cold starting, or from being blackened by insufficient preheating. |
