| 摘要 |
PROBLEM TO BE SOLVED: To drive a cathode tube constantly at a high efficiency to follow the optimum drive frequency which largely fluctuates in accordance with solid difference in the cathode tube or a piezoelectric transformer, or change by time or environments in a circuit to drive the cathode tube by the piezoelectric transformer without requiring adjusting work. SOLUTION: This device is provided with a voltage control oscillator 14 to change a drive frequency of a piezoelectric transformer 19, a current detecting circuit 12 to detect a current value flowing through a cathode tube 11 while the drive frequency is changed, an A/D converter 21, and a control part 22 to control the voltage control oscillator 14 to maximize current value flowing through the cathode tube 11, based on result of detection when the drive frequency of the piezoelectric transformer 19 is continuously changed. |
