| 摘要 |
PROBLEM TO BE SOLVED: To provide a power supply unit using a piezoelectric transformer which can output power ranging from low voltage of several 10 V to high voltage of several KV, and be stably controlled in outputting the high voltage power at an oscillation frequency near the resonant frequency of the piezoelectric transformer. SOLUTION: When an output voltage is low, the power supply unit simultaneously varies the frequency of an oscillation signal and the duty ratio thereof on the basis of an output voltage signal Sv to be fed back from an output section 40 so that a reference voltage indicating a target value of the output voltage may be the same as the output voltage, and raises the oscillation signal to generate a driving voltage of a piezoelectric transformer 20. On the contrary, when the output voltage is high, the power supply unit synchronizes the frequency of the oscillation signal with the oscillation signal of the piezoelectric transformer 20 on the basis of an oscillation signal Sf to be fed back from an oscillation frequency detecting section 30. Then, the power supply unit varies only the duty ratio of the oscillation signal on the basis of the output voltage signal Sv so that the reference voltage may be the same as the output voltage, and raises the oscillation signal to generate a driving voltage of the piezoelectric transformer 20. COPYRIGHT: (C)2008,JPO&INPIT
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