| 摘要 |
PURPOSE: To eliminate apprehension of shortening a life of a discharge lamp, and also to make a striation phenomenon hardly arise. CONSTITUTION: When a fluorescent lamp FL is preheated, under a condition where an oscillating frequency of an inverter circuit 1 is increased, filaments FLa, FLb are preheated. Because the oscillating frequency is high, impedance of a bypass capacitor C1 is lowered down, and due to allowing a current, flowing in a diode D1, resistor R1 and a positive temperature characteristic thermistor R2, to bypass flow in the bypass capacitor C1, a supply amount of a DC current component to the fluorescent lamp FL is decreased. When the fluorescent lamp FL is lighted, by decreasing a frequency, the impedance of the bypass capacitor C1 is increased, to increase the current flowing in the diode D1, resistor R1 and the positive temperature characteristic thermistor R2, and even when temporarily a striation phenomenon arises, by supplying a DC current, a striation is moved to prevent an apparent striation phenomenon from arising. |
