Bi-directional piezoelectric transformer based converter for high-voltage capacitive applications

A piezoelectric transformer based converter is presented in this paper, which not only is capable of generating high voltages, but also incorporates a bi-directional power stage. Applications of high capacitive loads, such as dielectric electro active polymers (DEAP) [1], often suffer from poor overall system efficiency, as only a small fraction of the supplied electrical energy is transferred to mechanical energy (<10%). The bi-directional power stage enables the recovery of the electrical energy stored in the highly capacitive load, improving the system efficiency significantly. The presented converter is capable of generating voltages of up to 1700V, from a 24V supply, and demonstrates efficiencies of up to 70%, which leads to a system efficiency improvement of 50%. The main achievements of this work are the demonstration of bi-directional functionality and energy recovery, as well as the investigation of the general behavior of the highly dynamic converter and the development of a new control strategy.