Piezoelectric transformer inverter

A piezoelectric transformer inverter comprising:

• a piezoelectric transformer having a pair of primary electrodes, one of which primary electrodes is grounded, which performs voltage conversion of an alternating input voltage or a direct current input voltage applied between the primary electrodes to supply an output voltage to a load connected to a secondary electrode of the piezoelectric transformer;
• a drive unit for supplying the alternating input voltage or the direct current input voltage between the primary electrodes of the piezoelectric transformer;
• a low-pass type resonance circuit unit inserted between an output of the drive unit and the primary electrodes of the piezoelectric transformer;
• a duty control unit for controlling an ON-Duty of the drive unit so that a value of a current flowing into the load coincides with a targeted current value;
• a phase-difference detection unit for detecting a phase difference between the input voltage and the output voltage of the piezoelectric transformer;
• and
• a frequency control unit for controlling a driving frequency of the drive unit so as to give the phase difference a specified value.