| 摘要 |
PROBLEM TO BE SOLVED: To enable highly efficient driving by converting the supply voltage of a power circuit through a drive circuit wherein a capacitor is series-connected with the input capacitance of a piezoelectric transformer, and outputting it. SOLUTION: A driving frequency is swept by an oscillator 34 from the side higher than the resonance frequency of a piezoelectric transformer 50 to the side lower than the resonance frequency, and sweep is stopped at a driving frequency appropriate to a preset Joule output voltage, the piezoelectric transformer 50 being driven at this driving frequency. The supply voltage of a power circuit wherein a power supply 10 is connected with a rectifying and smoothing circuit 20 is voltage-converted through a drive circuit 30 wherein a capacitor 33 is series-connected with the input capacitance of the driven piezoelectric transformer 50, and is outputted. As a result, the influence of driving frequency on resonance conditions can be reduced, and variation in driving waveform due to variation in driving frequency can be eliminated.
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