Fundamental limits on energy transfer and circuit considerations for piezoelectric transformers

This work investigates fundamental limits on the electromechanical energy conversion capacity of piezoelectric transformers by considering a work cycle analysis. Fundamental limitations are imposed by maximum electric field strength, maximum surface charge density, maximum stress and maximum strain. The authors' analysis indicates that the mechanical stress limit is the effective constraint in typical PZT materials. For a specific PZT-5H sample considered, a mechanical stress-limited work cycle indicates that this material can handle 330 W/cm/sup 3/ at 100 kHz. The theory of operation of soft-switching resonant drive circuitry is then discussed. Experimental results on a soft-switching inverter incorporating no magnetic components are reported.