| 摘要 |
PROBLEM TO BE SOLVED: To prevent a current supplied from a power source from exceeding a predetermined value, by detecting a current to be supplied to drive means, generating a pulse width modulation signal of a second frequency when the current value exceeds a predetermined value, periodically stopping drive means, and controlling a ratio during pulse width modulation signal. SOLUTION: A discharge tube connected to a secondary terminal of a piezoelectric transformer 110 and a drive circuit 19 for supplying a drive voltage of the resonance frequency to the piezoelectric transformer 110 are provided. Moreover, a frequency sweep oscillator 113 for detecting a load current flowing to a discharge tube, and supplying a first frequency to the drive circuit 19 so as to give a predetermined value to the load current, is provided. In addition, a power supply current limiting circuit 12 is provided in the drive circuit 19, which detects an input power supply supplied from a DC power source and generates a pulse width modulation(PWM) signal of a second frequency. Then, the drive circuit 19 is periodically stopped by the PWM signal, and the ratio is controlled during PWM signal so as to avoid the exceeding of the input current beyond the predetermined value. |
