Electrical Properties of a Piezoelectric Transformer for an AC-DC Converter

摘要

The electrical properties of a ring/dot piezoelectric transformer were analyzed for applications as an AC-DC converter using the step-down behavior of a piezoelectric transformer. The ring/dot piezoelectric transformer was prepared using Pb(Mn1/3Nb2/3)O-3 and Pb(Zn1/3Nb2/3)O-3 modified Pb(Zr,Ti)O-3 ceramics sintered at a relatively low temperature of 930 degrees C for 90 min. When the transformer was matched with a load resistance of 1000 Omega, it transferred a maximum power of 27 W. The maximum power was produced at a dc output voltage of 30 V and a matching load resistance of 1000 Omega While the manufactured ring/dot piezoelectric transformer released the maximum power at a resonance frequency of 71 kHz, the available frequency bandwidth was about 1 kHz at most due to strong frequency dependence of the piezoelectric transformer. The output dc current was highly improved up to 905 mA because no anisotropy of poling direction existed in the ring/dot piezoelectric transformer. Under a commercial input of 220 V-ac, AC-DC converter successfully produced 27 W at 30 V-dc and 905 mA.