| 摘要 |
<P>PROBLEM TO BE SOLVED: To shorten the time for an output voltage of a piezoelectric transformer to reach a target voltage. <P>SOLUTION: A power unit includes, for instance, a voltage controlled oscillator, a drive unit, a piezoelectric transformer, a frequency control unit, a holding unit, and a setting unit. The voltage controlled oscillator generates signals of a frequency corresponding to an inputted control voltage. The signals outputted from the voltage controlled oscillator are inputted to the drive unit. The piezoelectric transformer is driven by the drive unit according to the signals outputted from the voltage controlled oscillator. The frequency control unit makes the drive of the piezoelectric transformer by the drive unit be started at a predetermined initial frequency, and sweeps a frequency through the control voltage so as to turn the output voltage to a predetermined target voltage. The holding unit holds information indicating the control voltage equivalent to the frequency of the signals outputted by the voltage controlled oscillator when the output voltage from the power unit becomes the target voltage. The setting unit sets a sweep start frequency corresponding to the information held in the holding unit to the frequency control unit instead of the initial frequency. <P>COPYRIGHT: (C)2012,JPO&INPIT |
