| 摘要 |
PROBLEM TO BE SOLVED: To provide a discharge lamp lighting device which can detect mounting and dismounting of a discharge lamp by a simple configuration. SOLUTION: The waves of a voltage of commercial alternating current power supply (e) are rectified in a full wave rectifier circuit 14 to reduce the distortion in a low distortion circuit 21, and a self-excited inverter circuit 22 operates a transistor Q1 due to resonance of a series resonance circuit 23 and a return current of a current transformer CT1 and preheats and lights fluorescent lamps FL1, FL2. When either of the fluorescent lamps FL1, FL2 is removed, this discharge lamp lighting device detects a voltage of a capacitor C33 corresponding to a voltage of the transistor Q1 and applies it to a base of a transistor Q7 to increase impedance. Consequently, a gate voltage of an electric field- effect transistor Q3 is reduced, an apparent capacity of a capacitor C11 is reduced, a resultant capacitance of capacitors C11, C12 is reduced, and a base current of the transistor Q1 is reduced to reduce an output voltage of the self-excited inverter circuit 22. |
