Piezoelectric micro-transformer based on SOI structure

This paper presents the integration of a piezoelectric micro-transformer in a silicon substrate. The selected topology of the transformer takes advantage of the active materials like PZT. These structure is constituted by a unimorph circular membrane (PZT/silicon). Manufacturing process is compatible with MOSFET technologies. The application of this transformer is to achieve galvanic insulation in power converter to supply micro-systems requiring very low amount of energy. An analytical model has enabled us to determine the electric equivalent circuit of the transformer, to express the resonance frequencies and to plot the deflection and strain shapes of the membrane. A mechanical characterization has been carried out by interferometer and an electric characterization has been conducted with a first prototype.