Piezoelectric Transformers in Power Electronics

The increasing utilization of piezoelectric transformers (PT) in power electronics requires fundamental analysis and design of PT power converters. In addition, the possibility of overcoming the essential limitations of PT power ability by a combined operation of PTs needs to be examined. These studies could provide wide opportunities for PT exploitation in power electronic circuits. The main objective of this research is to develop generic models of PT power converters. We examine the output and input networks of the PT converter by utilizing a PT equivalent circuit. Obtaining PT equivalent circuit parameters from physical measurements is a problematic issue. Therefore, the first concern of the present work is to try to improve the earlier published methods of PT parameters determination in order to make them suitable for every kind of PT and to the conditions under which the given PT operates. The study proposes and verifies two novel methods for extracting PT equivalent parameters from measurements. A comparative analysis of the different types of rectifiers connected to the PT output is carried out in order to obtain generic models of PT AC/DC power converters. The methodology applied in this study follows the approach in which the PT output rectifier network is represented by an equivalent circuit that loads the PT as the corresponding rectifier. The unique nature of a PT allows innovative circuit design that ensures soft switching without matching inductors. This design substantially reduces the costs of electronic components in the circuit. Therefore another aim of the research is to develop a generic approach for achieving soft switching with no additional reactive elements at the input. To complete the work, the general requirements for the combined operation of several PTs are investigated.