Design considerations for achieving ZVS in a half bridge inverter that drives a piezoelectric transformer with no series inductor

A general procedure for maintaining soft switching in inductor-less half-bridge piezoelectric transformer (PT) inverter was analyzed by applying the equivalent circuit of the PT device. Soft switching capability of the PT was delineated and detailed guidelines are given for the load and frequency boundaries, voltage transfer function and the output voltage that will keep the operation under ZVS conditions. The analysis takes into account the maximum power dissipation of the PT, which is used to bind the permissible power transfer through the device. The analytical results for the half-bridge inductor-less PT inverter were verified by simulation and experiments for a radial vibration mode PT.