A resonantly driven piezoelectric transformer for high voltage generation

A resonant piezoelectric transformer circuit is being developed for high voltage generation. A lithium niobate ferroelectric crystal with a rotated y-cut polarization orientation is used as a step up transformer. The rectangular shaped crystal is driven through the thickness into the extensional vibration mode. Applied voltages at low radio frequencies, 40 to 90 kHz, are used, which includes the half and full wavelength resonance frequency. The circuit design takes advantage of the piezoelectric transformation into mechanical energy to bias the primary side of the transformer. An impedance matching transformer is used to match the crystal to the driving circuit over a wide range of frequencies. The piezoelectric circuit is designed to drive high impedances at 50 to 100 kV for beam or plasma applications. Voltage and frequency characteristics with several load impedances have been measured. The results of these tests to characterize the piezoelectric transformer circuit are presented.