DC-DC Power Conversion Using Smart Piezoelectric Transformers

Abstract

The attractiveness of the smart piezoelectric technology is mainly due to its desirable features of miniaturization and the extreme simplicity of the resulting components compared to widely used wire wound conventional magnetics. As a result, much attention has been focused on the application of Piezoelectric Transformer (PET) in high frequency switching power supplies as well as low profile inverters. Application of Rosen-PET in DC-DC power conversion is investigated. PET based step-up DC-DC converter, using phase locked loop(PLL) based control strategy to track optimal frequency is implemented. PET is excited by near-sinusoidal input without any DC offset to obtain optimal performance. Hardware prototype of the converter is fabricated and experimental performance is studied for different loading resistance conditions. Parallel operation of PETs is explored to obtain increased power level and finally Parallel-PET based DC-DC converter is developed and tested successfully. Details of overall converter design, hardware implementation and testing are given and experimental results are presented. I. INTRODUCTION PETs are special type of transformers which transform electrical energy into mechanical energy and back into electrical energy through mechanical vibrations. Lead zirconate titanate (PZT) or modified PZT-type ceramic materials are being used for PET applications with their unique properties like high quality factor, response speed and power density, compared to other materials. Also, both the sensing and actuating functions can be realized in the same material; the PET can be called as Smart PET. PETs offer certain features, which attract the interest of engineers and researchers, and these can be successfully used in power electronics. Based on their structure and vibration modes these are presently classified under, Rosen (Longitudinal), thickness, radial and contour extensional type PETs. With the improvement in material technology analysis-design tools, geometrical structure (single or multilayer, isolated or non-isolated) and fabrication technology, PET is being used in DC-DC, DC-AC, AC-DC applications [1-9]. PETs provide several advantages compared to magnetic ones due to their higher power densities, absence of electromagnetic noise, higher isolation voltages, high voltage conversion ratio and wide input voltage variation. Among the disadvantages of PETs, which seriously hinder their wider application, are the necessity of complex frequency tracking, modeling complexity, low bandwidth (BW) and the temperature dependency.