Step-down piezoelectric transformer using PZT-PMNS ceramics(II)

Lim, Kee-Koe,Park, Seong-Hee,Yun, Yong-Jin,Lee, Chung 충북대학교 컴퓨터정보통신 연구소 2005 컴퓨터정보통신연구 Vol.13 No.2

Piezoelectric transformers are expected to be small, thin and highly efficient, and which are attractive as a transformer with high power density for step down voltage. For these reasons, we have attempted to develop a step-down piezoelectric transformer for the miniaturized adaptor. We propose a piezoelectric transformer, operating in thickness extensional vibration mode for step-down voltage. This transformer consists of a multi-layered construction in the thickness direction. In order to develop the step-down piezoelectric transformers of 10 W class and turn ratio of 0.1 with high efficiency and miniaturization, the piezoelectric ceramics and piezoelectric transformer designs are estimated with a variety of characteristics. The basic composition of piezoelectric ceramics consists of ternary yPb(ZrxTi1-x)O3-(1-y)Pb(Mn1/3Nb1/3 Sb1/3)O3. In the piezoelectric characteristics evaluations, at y = 0.95 and x = 0.505, the electromechanical coupling factor(kp) is 58%, piezoelectric strain constant(d33) is 270 pC/N, mechanical quality factor(Qm) is 1520, permittivity(ε33T/ε0) is 1500, and Curie temperature is 350 ℃. At y = 0.90 and x = 0.500, kp is 56%, d33 is 250 pC/N, Qm is 1820, ε33T/ε0 is 1120, and Curie temperature is 290 ℃. It shows the excellent properties at morphotropic phase boundary regions. PZT-PMNS ceramic may be available for high power piezoelectric devices such as piezoelectric transformers. The design of step-down piezoelectric transformers for adaptor proposes a multi-layer structure to overcome some structural defects of conventional piezoelectric transformers. In order to design piezoelectric transformers and analyze their performances, the finite element analysis and equivalent circuit analysis method are applied. The maximum peak of gain G as a first mode for thickness extensional vibration occurs near 0.85 MHz at load resistance of 10 Ω. The peak of second mode at 1.7 MHz is 0.12 and the efficiency is 92%.

Improvement of Thermal Balance in Step-down Piezo Transformers with Ring-dot shapes

김인성,정순종,김민수,송재성,Vo Viet Thang 한국물리학회 2012 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.60 No.2

The design of ring-dot-shape piezoelectric transformers for thermal radiation is investigated in this paper. The temperature distribution at the center was improved by ring-dot shape. One of the most important factors affecting piezoelectric transformers is the temperature; hence, the piezoelectric material and construction should be improved to get transformers with higher power at a lower normal temperature increase. Obviously, internal losses generate heat, which increases the temperature of piezoelectric transformers, especially at high power, and changes the characteristics of the transformers. In this work, the modeling of a multilayer step-down piezoelectric transformer with a square shape with a central hole was studied using the ATILA software before its fabrication. Firstly, the parameters of a hard piezoelectric ceramic were measured from the fabricated specimens and used in the simulation. Moreover, the effects of frequency and load resistance on the electrical properties were studied. Then, on investigations of temperature at different load resistances and of the temperature distribution were carried out. Thus, the electrical properties and the temperature of step-down piezoelectric transformers corresponding to the simulation and fabricated by using piezoelectric ceramics were measured and compared to the simulated results. The design of ring-dot-shape piezoelectric transformers for thermal radiation is investigated in this paper. The temperature distribution at the center was improved by ring-dot shape. One of the most important factors affecting piezoelectric transformers is the temperature; hence, the piezoelectric material and construction should be improved to get transformers with higher power at a lower normal temperature increase. Obviously, internal losses generate heat, which increases the temperature of piezoelectric transformers, especially at high power, and changes the characteristics of the transformers. In this work, the modeling of a multilayer step-down piezoelectric transformer with a square shape with a central hole was studied using the ATILA software before its fabrication. Firstly, the parameters of a hard piezoelectric ceramic were measured from the fabricated specimens and used in the simulation. Moreover, the effects of frequency and load resistance on the electrical properties were studied. Then, on investigations of temperature at different load resistances and of the temperature distribution were carried out. Thus, the electrical properties and the temperature of step-down piezoelectric transformers corresponding to the simulation and fabricated by using piezoelectric ceramics were measured and compared to the simulated results.

Simulation and Parallel Connection of Step-down Piezoelectric Transformers

Vo Viet Thang,김인성,정순종,김민수,송재성 한국물리학회 2012 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.60 No.2

Piezoelectric transformers have been used widely in electronic circuits due to advantages such as high efficiency, miniaturization and no flammability; however the output power has been limited. For overcoming this drawback, some research has recently been focused on connections between piezoelectric transformers. Based on these operations, the output power has been improved compared to the single operation. Parallel operation of step-down piezoelectric transformers is presented in this paper. An important factor affecting the parallel operation of piezoelectric transformer was the resonance frequency, and a small difference in resonance frequencies was obtained with transformers having the same dimensions and fabricating processes. The piezoelectric transformers were found to operate in first radial mode at a frequency of 68 kHz. An equivalent circuit was used to investigate parallel driving of piezoelectric transformers and then to compare the result with experimental observations. The electrical characteristics, including the output voltage, output power and efficient were measured at a matching resistive load. Effects of frequency on the step-down ratio and of the input voltage on the power properties in the simulation were similar to the experimental results. The output power of the parallel operation was 35 W at a load of 50 and an input voltage of 100 V; the temperature rise was 30 C and the efficiency was 88%.

압전 변압기를 이용한 인버터식 네온관용 변압기에 관한 연구

변재영,김윤호 전력전자학회 2003 전력전자학회 논문지 Vol.8 No.6

In this paper, inverter type neon power supply using a piezoelectric transformer is fabricated and its characteristic is investigated. Developed neon power supply is composed of basic circuit and blocks, such as rectifier part, frequency oscillation part and piezoelectric transformer and resonant half bridge inverters. In this paper for complement the low power limitation, piezoelectric transformer at parallel connected driving by inverter is studied for neon tubes system of high power. When piezoelectric transformer is connected with parallel, LC filter connection method with parallel and selection of inductance L and capacitor C of primary side is suggested for reduce unbalanced current at the terminal of each transformer. Piezoelectric transformers use piezoelectric ceramic devices. Thus it is wireless therefore it has high power density, high isolation level, low loss, more light, and miniaturization. In addition, high voltage transfer ratio is expected because there is no leakage inductance. Also, it has economic merit that the electrical loss is low because structure is simple, small and lighter weight. 본 연구에서는 네온 변압기를 세라믹 계열의 압전 변압기를 이용한 인버터식 네온관용 변압기를 제안하였다. 인버터식 네온관용 압전 변압기의 주요 구성은 정류부, 발진부, 공진형 하프브릿지 인버터회로부 및 압전 변압기부로 구성 제작 하였다. 네온관용 변압기는 지금까지 개발된 압전 변압기 용량 보다 대부분 큰 용량을 필요로 하고 있기 때문에 압전 변압기의 용량 증가를 위해 병렬 구동하였다. 이때 병렬로 연결된 단층형 압전 변압기간 내부 임피던스 값의 불일치로 발생하는 불평형 전류를 최소화 하기 위하여 압전 변압기별로 LC 필터값을 분석 부착하여 전압의 왜곡율을 최소화 하여 안정된 정현파 출력을 구현하였다. 그리고 이를 컴퓨터 시뮬레이션 실험과 실제 네온관 부착 실험을 통하여 전력 밀도와 절연 레벨이 높고, 누설 자속이 없는 소형, 경량화된, 압전 변압기를 적용한 인버터식 네온관용 변압기가 기존의 자기식 네온관용 변압기 보다 우수함을 비교 입증 하였다.

Crescent-shaped Input Type 원형압전변압기의 특성 연구

정성수,박태곤,Jeong, Seong-Su,Park, Tae-Gone 한국전기전자재료학회 2006 전기전자재료학회논문지 Vol.19 No.7

This paper presents a new disk-type piezoelectric transformer. The input side of the transformer has a crescent-shaped electrode and the output side has a focused poling direction. The piezoelectric transformers operated in each transformer's resonance vibration mode. The electrodes and poling directions on commercially available piezoelectric ceramic disks were designed so that the planar or shear mode coupling factor $(k_p\;k_{15})$ becomes effective rather than the transverse mode coupling factor $(k_{31})$. ANSYS finite element code was used to analyze transformer behavior and to optimize electrode and poling configurations. The voltage step-up ratio of the proposed transformer has been markedly improved in comparison with that of the equivalent rectangular(Rosen) type. A single layer prototype transformer, $20\sim30mm$ in diameter and $1.0\sim3.5mm$ thick, was fabricated, such as step-up ratio, power transformation efficiency, and temperature were measured. While the transformer was driving a Cold Cathode Fluorescent Lamp(CCFL), the temperature field of the transformer was also observed.

Piezoelectric Properties of PMS-PZT with Bi2O3 and CeO2 for a Rosen-Type Transformer

H. K. Joo,I. S. Kim,J. S. Song,S. J. Jeong,M. S. Kim,S. H. Jeon 한국물리학회 2009 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.54 No.2

Recently, piezoelectric transformers have been applied to many fields. Multi layer piezoelectric transformers have the advantage of high step up ratio, high electromechanical coupling coeffcient (Kp) and high mechanical quality factor (Qm), but they are subject to the peeling phenomenon and the need for an increased sintering temperature made the price of costly electrodes. Thus, in this study, we discuss a method to fabricate of high-power Rosen-type piezoelectric transformers. The high-power Rosen-type piezoelectric transformers were synthesized using 0.05Pb(Mn1=3Sb2=3)O3- 0.48PbZrO3-0.47PbTiO3 (abbreviated as PMS-PZT) ceramics. The density, the microstructure and the dielectric and piezoelectric properties as functions of the sintering temperature were investigated and an addition of Bi2O3 and CeO2 resulted in a significant improvement in the piezoelectric properties. The results indicated that the following optimal properties of ceramics were obtained at a sintering temperature of 1200℃:εr = 880, tanδ = 0.0075, Kp = 0.57, Qm = 1124 and d33 = 304 pC/N. Recently, piezoelectric transformers have been applied to many fields. Multi layer piezoelectric transformers have the advantage of high step up ratio, high electromechanical coupling coeffcient (Kp) and high mechanical quality factor (Qm), but they are subject to the peeling phenomenon and the need for an increased sintering temperature made the price of costly electrodes. Thus, in this study, we discuss a method to fabricate of high-power Rosen-type piezoelectric transformers. The high-power Rosen-type piezoelectric transformers were synthesized using 0.05Pb(Mn1=3Sb2=3)O3- 0.48PbZrO3-0.47PbTiO3 (abbreviated as PMS-PZT) ceramics. The density, the microstructure and the dielectric and piezoelectric properties as functions of the sintering temperature were investigated and an addition of Bi2O3 and CeO2 resulted in a significant improvement in the piezoelectric properties. The results indicated that the following optimal properties of ceramics were obtained at a sintering temperature of 1200℃:εr = 880, tanδ = 0.0075, Kp = 0.57, Qm = 1124 and d33 = 304 pC/N.

PMN-PZN-PZT 세라믹스를 이용한 적층형 압전변압기의 전기적 특성

이창배,류주현,백동수,강진규,조봉희,이성일,Lee, Chang-Bae,Yoo, Ju-Hyun,Paik, Dong-Soo,Kang, Jin-Kyu,Cho, Hong-Hee,Lee, Sung-Ill 한국전기전자재료학회 2006 전기전자재료학회논문지 Vol.19 No.7

Dielectric and piezoelectric properties of PMN-PZT ceramics with a high mechanical quality factor$(Q_m)$ and a low temperature sintering temperature were investigated as a function of PZN substitution in order to develop multilayer piezoelectric transformer for AC-DC converter. Multilayer piezoelectric transformers were subsequently manufactured using the PMN-PZN-PZT ceramic offering the optimal behavior and then the electrical performance were invetigated. At the sintering temperature of $940^{\circ}C$, density, electromechanical coupling factor$(k_p)$, mechanical qualify factor$(Q_m)$ and dielectric constant$(\varepsilon_r)$ of 8 mol% PZN substituted specimen were $7.73g/cm^3$, 0.524, 1573 and 1455, respectively. The PZN substitution caused a increase in the dielectric constant and the electromechnical coupling factor. The voltage step-up ratio of multilayer piezoelectric transformer showed the maximum value at near the resonant frequency of 76.55 kHz and increased according to the increase of load resistance. The multilayer piezoelectric transformer with the output impedance coincided with the load resistance showed the temperature increase of less than $20^{\circ}C$ at the output power of 10 W. Based on the results, the manufactured multilayer transformer using the low temperature sintered PMN-PZN-PZT ceramics can be stably driven for both step-up and down transformers.

Electrical Properties of a Piezoelectric Transformer for an AC-DC Converter

박용욱 한국물리학회 2010 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.57 No.41

The electrical properties of a ring/dot piezoelectric transformer were analyzed for applications as an AC-DC converter using the step-down behavior of a piezoelectric transformer. The ring/dot piezoelectric transformer was prepared using Pb(Mn1/3Nb2/3)O3 and Pb(Zn1/3Nb2/3)O3 modified Pb(Zr,Ti)O3 ceramics sintered at a relatively low temperature of 930 ℃ for 90 min. When the transformer was matched with a load resistance of 1000 Ω, it transferred a maximum power of 27 W. The maximum power was produced at a dc output voltage of 30 V and a matching load resistance of 1000 Ω. While the manufactured ring/dot piezoelectric transformer released the maximum power at a resonance frequency of 71 kHz, the available frequency bandwidth was about 1 kHz at most due to strong frequency dependence of the piezoelectric transformer. The output dc current was highly improved up to 905 mA because no anisotropy of poling direction existed in the ring/dot piezoelectric transformer. Under a commercial input of 220 Vac, AC-DC converter successfully produced 27 W at 30 Vdc and 905 mA.

PSN-PZT계 세라믹스를 이용한 고출력 압전 트랜스포머의 전기적 특성

이용우,류주현,윤광희,정회승,서성재,김종선 한국전기전자재료학회 2000 전기전자재료학회논문지 Vol.13 No.4

In this paper we investigated the structural dielectric and piezoelectric properties of 0.03Pb(Sb$\_$1/2//Nb$\_$1/2/)-0.97Pb(Zr$\_$0.495//Ti$\_$0.505/)O$_3$+0.5 wt% excess PbO + wt% MnO(X=0, 0.1, 0.3, 0.5, 0.7) ceramics to develop the high-power piezoelectric transformer. The piezoelectric transformers with dimension of 27.5$\times$27.5$\times$2.5[mm$^3$]were fabricated and their electrical properties were measured. Maxima of piezoelectric properties such as electro-mechanical coupling factor of 0.534 and mechanical quality factor of 1487 were obtained for the PSN-PZT with 0.3wt% MnO. voltage step-up ratios of piezoelectric transformers at 500[Ω]and no load were 0.78, 12.82, respectively. The maximum efficiency of piezoelectric transformer was 98.6% at 800[Ω]. While the 14W fluorescent lamp were driven by the piezoelectric transformer for more than 20[min], increment of temperature in the piezoelectric transformer was 7[$\^{C}$].

Device and Piezoelectric Characteristics of Pb(Mn1/3Sb2/3) O3-PZT Ceramics for Piezoelectric Transformer

Sohn, Joon-Ho,Heo, Soo-Jeong,Sohn, Jeong-Ho,Lee, Joon-Hyung,Jung, Woo-Hwan,Kim, Dong-Bum,Cho, Sang-Hee The Korean Ceramic Society 1999 The Korean journal of ceramics Vol.5 No.2

In the $(Pb_{1-x}M_x)[(Mn_{1/3}Sb_{2/3})_{0.05}Zr_yTi_{0.95-y}]O_3$ system, where M=Ca and Sr, the piezoelectric properties were evaluated to examine the possibility of application to piezoelectric transformer. A Rosen-type piezoelectric transformer was formed, then the electrical properties of voltage step-up ratio, frequency characteristics etc. were analysed. The morphotropic phase boundary was determined to be y=0.475 in $Pb[(Mn_{1/3}Sb_{2/3})_{0.05}Zr_yTi_{0.95-y}]O_3$ system and the piezoelectric properties of this composition was kp=0.59, Qm=1600 and $\varepsilon_r$=1150. Moreover, when 1-2 mol% of Sr are substituted, enhanced piezoelectric properties of kp=0.61, Qm=1600 and $\varepsilon_r$=1400 were shown. The temperature rising (ΔT) of a piezoelectric transformer with $Pb[Mn_{1/3}Sb_{2/3})_{0.05}Zr_{0.475}Ti_{0.475})]O_3 $ composition was $10^{\circ}C$, and the voltage step-up ratio was 500 when the output voltage was 4000V, whereas the ΔT was below $3^{\circ}C$ and the resonant frequency variation ($\Delta f_r$) as a function of load resistance was below 5% when the output voltage was 2000 V. These characteristics are superior to the properties of materials, which were substituted by Ca or without substitution.