A ring-shaped piezoelectric transformer operating in the third symmetric extensional vibration mode

Abstract In this study, a ring-shaped piezoelectric transformer operating in the third symmetric extensional vibration mode is proposed, and its characteristics are investigated. The transformer consists of a lead zirconate titanate (PZT) ceramic ring with a high mechanical quality factor which has an outer diameter of 12.7 mm, an inner diameter of 5.1 mm and a thickness of 1.2 mm. The transformer is poled along the thickness direction. The top surface is covered by two ring-shaped electrodes separated by a narrow annular gap, and the regions covered by the outer and inner ring electrodes serve as the input and output parts of the transformer, respectively. Its bottom surface is fully covered with a silver electrode. For a temperature rise of 20°C, the transformer has an output power of 1.8 W and a power density of 14.3 W/cm3. With a matching load resistance of 860 Ω, its maximum efficiency is 92.3%, and the maximum voltage gain is 1.9. When two ring-shaped transformers are connected in parallel, the total output power is significantly higher than that of a single ring-shaped transformer. However, the resultant maximum efficiency is slightly less than that of a single transformer, and the transformer with the lower voltage ratio determines the overall voltage gain of the parallel combination.

[1]  Kazumasa Ohnishi,et al.  Presentation of a New Equivalent Circuit of a Piezoelectric Transformer under High-Power Operation , 1999 .

[2]  S. Hirose,et al.  New design method of piezoelectric transformer considering high-power characteristics of various composition ceramics , 1998, 1998 IEEE Ultrasonics Symposium. Proceedings (Cat. No. 98CH36102).

[3]  Y. Fuda,et al.  Piezoelectric Transformer for Cold Cathode Fluorescent Lamp Inverter , 1997 .

[4]  S. Kawashima,et al.  Third order longitudinal mode piezoelectric ceramic transformer and its application to high-voltage power inverter , 1994, 1994 Proceedings of IEEE Ultrasonics Symposium.

[5]  K. Nakamura,et al.  PIEZOELECTRIC TRANSFORMERS USING LINBO3 SINGLE CRYSTALS , 1998 .

[6]  Kenichi Kato,et al.  STEP-DOWN TRANSFORMER UTILIZING THE PIEZOELECTRIC TRANSVERSAL EFFECT , 1998 .

[7]  Junhui Hu,et al.  A Study on the Rectangular-Bar-Shaped Multilayer Piezoelectric Transformer Using Length Extensional Vibration Mode , 1999 .

[8]  K. Raney,et al.  High Voltage Ceramic Transformers , 1962 .

[9]  N. Wakatsuki,et al.  Investigation of Internal Loss and Power Transmission Characteristic of Width Shear Vibration Piezoelectric Transformer , 1994 .

[10]  C. L. Choy,et al.  An improved method for analyzing the performance of multilayer piezoelectric transformers , 1999, 1999 IEEE Ultrasonics Symposium. Proceedings. International Symposium (Cat. No.99CH37027).

[11]  C. A. Rosen Ceramic transformer and filters , 1956 .

[12]  Yasuhiro Sasaki,et al.  Piezoelectric ceramic transformer operating in thickness extensional vibration mode for power supply , 1992, IEEE 1992 Ultrasonics Symposium Proceedings.