Patent ID: 8350550

Claim:
A power unit comprising: an oscillator configured to generate a clock signal; a frequency division device configured to divide the clock signal in a second frequency division ratio based on a first frequency division ratio and to output a driving pulse; a switching device driven by the driving pulse; a piezoelectric transformer configured to output an alternating-current high voltage from a secondary side thereof when a voltage is intermittently applied to a primary side thereof by the switching device; a converting device configured to convert an analog signal corresponding to the high voltage output of the piezoelectric transformer into a digital signal and to output the digital signal; a comparison device configured to compare the digital signal with a target voltage set for the high voltage output of the piezoelectric transformer and to output a comparison result; a controller configured to control the first frequency division ratio on the basis of the comparison result; a first frequency division ratio holding device configured to hold the first frequency division ratio controlled by the controller; a first computing device configured to determine the second frequency division ratio by performing computation using a first correction value and the first frequency division ratio held by the first frequency division ratio holding device; and a second frequency division ratio holding device configured to hold the second frequency division ratio determined by the first computing device.