Piezoelectric ceramic transformer operating in thickness extensional vibration mode for power supply

Abstract

A new kind of multilayer piezoelectric ceramic transformer for switching regulated power supplies is described. This transformer operates in the second thickness extensional vibration mode. Its resonant frequency is higher than 1 MHz. Theoretical calculations are implemented using a distributed constant electromechanical equivalent circuit method. It is calculated that this transformer can operate with higher than 90% efficiency. A fabricated transformer is examined. PbTiO/sub 3/ family ceramics are used because of the large anisotropy between electromechanical coupling factors. Results indicate that the piezoelectric transformer has good resonant characteristics, with little spurious vibration, and exhibits 16 W/cm/sup 3/ power density with high efficiency at 2 MHz. A switching regulated power supply, applying the piezoelectric transformer, is built and examined. >