Patent ID: 7579749
Filing Date: 2009-08-25
Classification: G03G,H01L

Abstract:
1. A power supply device that generates an output voltage by driving a piezoelectric transformer using a frequency signal, comprising: a comparison unit configured to compare an output voltage and a voltage setting signal that sets the output voltage; and a voltage control oscillation unit configured to generate the frequency signal to drive the piezoelectric transformer based on comparison results of the comparison unit, wherein frequency characteristics of the piezoelectric transformer when driving the piezoelectric transformer using the frequency signal include a resonant frequency of the piezoelectric transformer at which a maximum voltage is output and a plurality of spurious resonant frequencies of the piezoelectric transformer, the plurality of spurious resonant frequencies being higher than the resonant frequency and at which a voltage lower than the maximum voltage is output, and wherein the voltage control oscillation unit generates the frequency signal within a range between the resonant frequency and a closest spurious resonant frequency to the resonant frequency among the plurality of spurious resonant frequencies, sets an initial frequency of the frequency signal for driving the piezoelectric transformer to be lower than the closest spurious resonant frequency, and sweeps a frequency from the set initial frequency to a frequency corresponding to a target voltage.