Piezoelectric Transformer for AC-DC converter

Abstract

A new piezoelectric transformer for AC-DC converter is presented. This piezoelectric transformer, with a multilayered construction in the thickness direction, operates contour-extensional vibration mode. Output impedance of the transformer is designed to be low in order to match load impedance, approximately several tens of ohm. We fabricated a transformer whose dimensions are 14mm long, 14mm wide and 5.8mm thick and examined it. It was found that the transformer exhibited a 0.4 voltage gain and 96.3% efficiency at 135kHz, when the temperature increase was 30°C. We applied the transformer to the fabrication of an AC-DC converter. The converter showed a good line and load regulation, and the highest efficiency of 90.2% was obtained.