Self-Matching Circuitof Lead-Free Piezoelectric High Voltage Generator

A piezoelectric transformer is an electro-mechanical device that transfers electrical through a mechanical vibration at its resonance frequency.In general,piezoelectric transformers provide many advantages over convention electromagnetic transformers, such as:high efficiency,small size,light weight,explosion-proof,non-flammable, anti-over-current,no electromagnetic interference and so on.It is the indispensable part in the electronic information system.Since proposed by Rosen in 1950s,the study of piezoelectric transformer get more significant progress,with the emergence of the high K and Q_m piezoelectric material of lead-based(PbZrTiO₃).However,these materials contain more than 70%PbO,they cause environmental pollution.The application of lead-free piezoelectric materials is limited because of its lower performance,such as:piezoelectric activity,K,Q_m,etc. Domestic and foreign scientific research institutions and companies have made a breakthrough in technology and economic aspects in the lead-free piezoelectric transformer,but many problems still exist,for example,lack of circuit driving techniques.By studying the modification of KNNT-based piezoelectric materials,the doping of KCN and proper amount of MnO₂ was effective in promoting the mechanical quality factor Q_m and reducing the dielectric loss tanδ.The high performance KNNT piezoelectric materials with 1mol%K₄CuNb₈O₂₃,0.5mol%MnO₂ was obtained. Piezoelectric transformers are fabricated using KNNT-based piezoelectric materials with 1mol%K₄CuYb₈O₂₃,0.5mol%MnO₂.In this thesis,the characteristics of lead-free piezoelectric ceramics and the driving circuit adaptive characteristics,applications of high-voltage generator have been studied.1.From the theory of disk-type piezoelectric transformers developed,the equivalent electrical model of single-layer disc-type piezoelectric transformer is set up.2.Disk-type piezoelectric transformers are fabricated using modified(K_0.5Na_0.5) (Nb_0.9Ta_0.1)O₃ ceramics.3.According to the characteristics of lead-free piezoelectric transformer, programmable pre-boost circuit is designed.4.A half-bridge driver circuit with adaptive sweep has been designed to identify and track automatically the resonant frequency of piezoelectric transformer.5.A high voltage drive for CCFL has been designed,which is based on lead-free piezoelectric transformer.6.With lead-free piezoelectric transformer,a high-pressure device for piezoelectric materials polarized has been developed.The research on the application of lead-free piezoelectric transformer is valuable.