| 摘要 |
PROBLEM TO BE SOLVED: To provide a cold cathode-ray tube lighting device capable of restricting the fluctuation of the driving frequency at the time of bursting off a circuit for controlling the driving frequency with the burst modulated light. SOLUTION: This cold cathode-ray tube device controls driving frequency while monitoring the tube current flowing in a cold-cathode ray tube 2. This driving frequency is controlled at a higher frequency side than the natural resonance frequency of a piezoelectric transformer 1, and a burst control circuit 4 for changing the duty at a frequency sufficiently lower than the driving frequency in response to the input light modulating voltage and a frequency control circuit 3 are connected to a driving circuit 5, and the driving circuit 5 drives the piezoelectric transformer 1 on the basis of the signal from both the control circuits. The frequency control circuit 3 includes a current and voltage converting circuit 31, a rectifying circuit 32, a comparing circuit 33, an integrating circuit 34 and a frequency converting circuit 35, and controls so as to lower the driving frequency when lowering of the input voltage of the frequency converting circuit 35 is detected and so as to raise the driving frequency when the voltage at this point is raised. |
