| 摘要 |
PROBLEM TO BE SOLVED: To provide a lighting circuit for a cold cathode discharge tube suppressing generation of asymmetricity of a tube current waveform and suppressing deviation of luminance of a tube axial direction and reduction of effective mercury by preventing moving of mercury, and a lighting system reducing unevenness of luminance by using the lighting circuit and having no risk of lowering luminance due to a short life. SOLUTION: A phase difference of amplitude intensity and a fundamental wave of each higher harmonic component of the tube current waveform is compared with a value set in advance. When the phase difference with the amplitude intensity or the fundamental wave exceeds the value set in advance, an oscillation circuit changes a driving frequency to suppress generation of asymmetricity of the tube current waveform. COPYRIGHT: (C)2004,JPO |
