A piezoelectric transformer includes a rectangular plate-shaped piezoelectric board having a length L in a longitudinal direction. In the piezoelectric board, five regions having a length L/5 are formed. In the two of regions, inner electrodes are formed in a thickness direction and conducted to outer electrodes provided in these regions. In a third region, outer electrodes are provided. The two regions of the piezoelectric board are polarized in the thickness direction, and two adjacent regions thereof are polarized in the longitudinal direction, and the third region is non-polarized. When a voltage is applied to the outer electrodes, the piezoelectric board expands and contracts in the longitudinal direction due to a piezoelectric effect. Thus, a piezoelectric transformer which enables high-efficient energy conversion even when a driving frequency is increased and a wireless power transmission system using the piezoelectric transformer are provided.
展开▼
