A comparison of 1D analytical model and 3D finite element analysis with experiments for a rosen-type piezoelectric transformer.

This article is dedicated to the study of Piezoelectric Transformers (PTs), which offer promising solutions to the increasing need for integrated power electronics modules within autonomous systems. The advantages offered by such transformers include: immunity to electromagnetic disturbances; ease of miniaturisation for example, using conventional micro fabrication processes; and enhanced performance in terms of voltage gain and power efficiency. Central to the adequate description of such transformers is the need for complex analytical modeling tools, especially if one is attempting to include combined contributions due to (i) mechanical phenomena owing to the different propagation modes which differ at the primary and secondary sides of the PT; and (ii) electrical phenomena such as the voltage gain and power efficiency, which depend on the electrical load. The present work demonstrates an original one-dimensional (1D) analytical model, dedicated to a Rosen-type PT and simulation results are successively compared against that of a three-dimensional (3D) Finite Element Analysis (COMSOL Multiphysics software) and experimental results. The Rosen-type PT studied here is based on a single layer soft PZT (P191) with corresponding dimensions 18 mm × 3 mm × 1.5 mm, which operated at the second harmonic of 176 kHz. Detailed simulational and experimental results show that the presented 1D model predicts experimental measurements to within less than 10% error of the voltage gain at the second and third resonance frequency modes. Adjustment of the analytical model parameters is found to decrease errors relative to experimental voltage gain to within 1%, whilst a 2.5% error on the output admittance magnitude at the second resonance mode were obtained. Relying on the unique assumption of one-dimensionality, the present analytical model appears as a useful tool for Rosen-type PT design and behavior understanding.

Reducing crosstalk in array structures by controlling the excitation voltage of individual elements: a feasibility study.

This paper describes a procedure to minimize crosstalk between the individual elements of a piezoelectric transducer array. A two-dimensional finite elements model was developed and the excitation voltages predicted by the model were applied to the array prototypes made of PZT 27 ceramic. Symmetric and asymmetric linear phased arrays operating at approximately 450 kHz were tested in the feasibility study. The studies were carried out at low frequency to facilitate the fabrication of the transducer arrays and to check the feasibility in this case. The novelty of our approach is to offer active cancellation of crosstalk in transducer arrays generating continuous waves, even in the presence of fabrication defects. The experimental results showed the validity of the approach and demonstrated that crosstalk can be reduced by about 6-10 dB. In ultrasonic imaging systems, this method could be introduced by using a multichannel generator providing electrical signals containing both phased signals required to focalize and deflect the acoustic beam associated with the correction signals.