| 摘要 |
PURPOSE:To provide a discharge lamp lighting unit which improves crest factor. CONSTITUTION:A rectifying circuit 11 rectifies the full waves of a commercial power source E, and a partial smoothing circuit 12 smoothes it partially, and high frequency is oscillated by turning on the transistors Q1 and Q2 of an inverter circuit 13 alternately. A low frequency voltage detecting circuit 15 detects the peak of the voltage, and also a high frequency voltage detecting circuit 14 detects the peak of the voltage of a high frequency voltage detecting circuit 14. The peak of the voltage detected by the high frequency voltage detecting circuit 14 and the peak of the voltage detected by the low frequency voltage detecting circuit 15 are superposed on each other, and the superposed one is inputted into the inversion input terminal of an air lamp 17. The air lamp 17 compares it with the voltage of a reference voltage source E1 and outputs it, and An OSC controller 18 converts voltage into frequency, and a drive circuit 19 changes the oscillated frequency of transistors Q1 and Q2, and changes the oscillated frequency of an inverter circuit 13, whereby the currents of fluorescent lamps FL1 and FL2 are made into approximately constant values. |
