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%.

Modeling and Investigation of Multilayer Piezoelectric Transformer with a Central Hole for Heat Dissipation

Vo Viet Thang,Insung Kim,Soonjong Jeong,Minsoo Kim,Jaesung Song 대한전기학회 2011 Journal of Electrical Engineering & Technology Vol.6 No.5

A multilayer square-type piezoelectric transformer with a hole at the center was investigated in this paper. Temperature distribution at the center was improved by using this construction, therefore increasing input voltage and output power. This model was simulated and investigated successfully by applying a finite element method (FEM) in ATILA software. An optimized structure was then fabricated, examined, and compared to the simulation results. Electrical characteristics, including output voltage and output power, were measured at different load resistances. The temperature distribution was also monitored using an infrared camera. The piezoelectric transformer operated at first radial vibration mode and a frequency area of 70 ㎑. The 16 W output power was achieved in a three-layer transformer with 96% efficiency and 20 ℃ temperature rise from room temperature under 115 V driving voltage, 100 Ω matching load, 28 x 28 x 1.8 ㎜ size, and 2 mm hole diameter. With these square-type multilayer piezoelectric transformers, the temperature was concentrated around the hole and lower than in piezoelectric transformers without a hole.

Investigation of the Optimum Design for a 10 W Step-down 3-layer Piezoelectric Transformer

Vo Viet Thang,김인성,주현규,정순종,김민수,송재성 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.58 No.31

This paper presents the electrical properties of a step-down multilayer piezoelectric transformer with square shape fabricated with a piezoelectric ceramic. ATILA, a modeling program, was used to simulate the piezoelectric transformer, and its results were compared to these of practical experiment. A 3D model with the size corresponding to the experiment was created in the ATILA program. Simulated parameters, including the excitation voltage, material factors, polarization, and boundary conditions, and two types of analyses (modal and harmonic) were used to present and calculate the property of piezoelectric transformer. The frequency dependence of the step-down ratio and the input voltage dependence of power properties in the simulation were similar to the experiment results. Through a comparison with experiment, the potential profile in the model is described visually for different loads and frequencies. A power of 10 W was achieved at load of 100 Ω and an input voltage of 60 V, for which the temperature rise was less than 20 ℃.

Modeling and Investigation of Multilayer Piezoelectric Transformer with a Central Hole for Heat Dissipation

Thang, Vo Viet,Kim, In-Sung,Jeong, Soon-Jong,Kim, Min-Soo,Song, Jae-Sung The Korean Institute of Electrical Engineers 2011 Journal of Electrical Engineering & Technology Vol.6 No.5

A multilayer square-type piezoelectric transformer with a hole at the center was investigated in this paper. Temperature distribution at the center was improved by using this construction, therefore increasing input voltage and output power. This model was simulated and investigated successfully by applying a finite element method (FEM) in ATILA software. An optimized structure was then fabricated, examined, and compared to the simulation results. Electrical characteristics, including output voltage and output power, were measured at different load resistances. The temperature distribution was also monitored using an infrared camera. The piezoelectric transformer operated at first radial vibration mode and a frequency area of 70 kHz. The 16 W output power was achieved in a three-layer transformer with 96% efficiency and $20^{\circ}C$ temperature rise from room temperature under 115 V driving voltage, 100 ${\Omega}$ matching load, $28{\times}28{\times}1.8mm$ size, and 2 mm hole diameter. With these square-type multilayer piezoelectric transformers, the temperature was concentrated around the hole and lower than in piezoelectric transformers without a hole.

Guidance of Nerve Stimulator and Ultrasound for Transforaminal Epidural Steroid Injection in Lumbosacral Radicular Pain : A Single Institution Experience in Vietnam

Viet-Thang Le,Chi Hue Nguyen,Phuoc Trong Do,Anh Minh Nguyen,Khoi Hong Vo 대한신경외과학회 2024 Journal of Korean neurosurgical society Vol.67 No.2

Objective : This study aimed to evaluate the clinical feasibility of the combination of ultrasound and nerve stimulator guidance in transforaminal epidural steroid injections (TESIs) to manage lumbosacral chronic radicular pain. Methods : Using the combination of nerve stimulator and ultrasound guidance, TESIs were performed in 125 segments of 78 patients who presented with chronic lumbar radicular pain. Demographic characteristics and surgical outcomes were recorded on admission, pre-procedural and post-procedural for 1-week, 1-month, 3-month, and 6-month follow-ups. The result was measured using the Numeric rating scale (NRS) and Oswestry disability index (ODI). Results : Patients who received TESIs showed significant improvements on two evaluation tools (NRS, ODI), compared to that before procedure (p<0.001). No significant complications were observed for 6 months’ follow-up. Conclusion : The result suggests that a combination of ultrasound and nerve stimulator guidance in transforaminal epidural injections is safe, reliable and effective for short-term management of lumbar disc herniation. It is a promising technique and has shown good results in providing intermediate pain relief.

스마트 폰을 사용한 움직임 패턴 기반 넘어짐 감지

보비에트 ( Viet Vo ),황민탕 ( Thang Minh Hoang ),이창무 ( Chang-moo Lee ),최덕재 ( Deok-jai Choi ) 한국인터넷정보학회 2012 인터넷정보학회논문지 Vol.13 No.4

인간의 동작 인식은 건강관리, 상황기반 응용 등 실제적인 삶의 여러 부분에서 이용할 수 있기 때문에 중요한 주제이다. 건강관리를 위한 조언을 제공하는데 사용될 수 있기 때문에 동작인식 중 일상생활 동작인식이 주로 연구되고 있다. 특별히 넘어짐은 심장문제로 발생할 수 있기 때문에 넘어짐 인식은 독거 노인의 건강한 삶에 중요한 역할을 할 수 있다. 넘어짐 인식은 여전히 어려운 연구과제이다. 넘어짐 인식을 위해 몸에 여러 종류의 센서를 부착하는 시스템이 제안되었지만 이는 사용자가 센서를 부착하는 것을 잊어버리거나 이런 시스템에 익숙하지 않기 때문에 유용성에 문제가 있다. 본 연구에서는 사용자가 휴대하고 있는 스마트 폰 내의 가속도 및 자이로센서 값의 변화를 분석하여 알려진 넘어짐 패턴과 유사성을 분석하여 넘어짐을 판단하는 방법을 제안한다. 이 연구를 위해 5명의 자원자를 모집하여 다양한 종류의 넘어짐을 실험하였다. 실험결과는 본 연구를 통해서 넘어짐 인식을 위한 제안한 방식이 유효하다는 것을 보여준다. 실험 알고리즘은 많이 사용되고 있는 G1 스마트 폰 위에 구현하였다. Nowadays, recognizing human activities is an important subject; it is exploited widely and applied to many fields in real-life, especially in health care and context aware application. Research achievements are mainly focused on activities of daily living which are useful for suggesting advises to health care applications. Falling event is one of the biggest risks to the health and well-being of the elderly especially in independent living because falling accidents may be caused from heart attack. Recognizing this activity still remains in difficult research area. Many systems equipped wearable sensors have been proposed but they are not useful if users forget to wear the clothes or lack ability to adapt themselves to mobile systems without specific wearable sensors. In this paper, we develop a novel method based on analyzing the change of acceleration, orientation when the fall occurs and measure their similarity to featured fall patterns. In this study, we recruit five volunteers in our experiment including various fall categories. The results are effective for recognizing fall activity. Our system is implemented on G1 smart phone which are already plugged accelerometer and orientation sensors. The popular phone is used to get data from accelerometer and results showthe feasibility of our method and significant contribution to fall detection.

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.

Fabrication of Carbon Nanotubes on Tungsten Tips

Phan Ngoc Hong,Phan Ngoc Minh,Vo Viet Cuong,Bui Hung Thang,Phan Hong Khoi 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.52 No.5

In this paper, we present the results of fabrication of carbon nanotubes on sharp W tips for advanced electron emiters and scanning probe microscopy. A calculation to optimize the elec- trochemical etching conditions for geting ultra-sharp W tips was caried out. W tips of 50 nm in diameter were formed by electrochemical etching of a 0.3-mm W wire in a 5 % KOH solution. Fe catalytic nanoparticles were deposited at the apex of the W tip by electroplating in a FeCl3 solution. By using hot-lament chemical vapor deposition in C2H2/H2 gases, we have sucesfuly grown individual CNTs of 4 m in length and 20 nm in diameter on a W tip.

Output Power of a Ring-type Stacked Piezoelectric Transformer with Pure Ag Electrodes

김인성,주현규,정순종,김민수,송재성,Vo Viet Thang 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.58 No.31

In this research, the electrical properties of a ring-type step-down stack piezoelectric transformer with pure Ag electrodes were investigated using simulated models and practical experiments. A prototype of the transformer was fabricated, 30 mm in diameter and 3 mm in total thickness, using a piezoelectric ceramic. In this design, the isolated gap between the input and the output sections was 1.5 mm, and a no-printed area existed. The 3D model with a size corresponding to the experiment was created in the simulation. The voltage step-down ratio and the power increased with increasing input voltage at resonant frequency. In the simulation, the potential distribution in the model was described, and the potential at any node could be shown. At an output power of 5 W, the transformer characteristics across a 150 Ω load were found to be an input voltage of 100 V and a temperature rise of less than 20 ℃ from room temperature.

Properties of Step-down Multilayer Piezo Stack Transformers Using PNN-PMN-PZT Ceramics with CeO_2 Addition

김인성,김민수,정순종,송재성,주현규,Vo Viet Thang,Alexandru Muller 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.58 No.31

In order to fabricate multilayer piezo stack transformers, we investigated the influences of the sintering temperature and the dielectric and piezoelectric properties of Pb(Ni_(1/3)Nb_(2/3))-Pb(Mn_(1/3)Nb_(2/3))-Pb(Zr_(0.505)Ti_(0.495))O_3 (PNN-PMN-PZT) ceramics with CeO_2 additives due to their effects of grain growth suppression. Meanwhile, the effects of CeO_2 additives on the microstructure and the electrical properties of PNN-PMN-PZT were investigated in detail. In addition, multilayer piezo stack transformers with the composition of PNN-PMN-PZT were fabricated, and the characteristics were measured for various load resistances at resonance frequency. The voltage stepup ratio was continuously changed with increasing input voltage and load resistance. The output voltages and powers were increased with increasing input voltage at matching impedance. The temperature rise of the multilayer piezo stack transformer increased with increasing input voltage and load resistance. These results indicate that the optimized properties of ceramics, d_(33) = 274 pC/N, K_p = 0.55, Q_m = 2581, ε_r = 1474, density = 7.899 g/cm^3, and tanδ = 0.0031, were obtained at a sintering temperature of 1250 ℃. Meanwhile, multilayer piezo stack transformers a sintered at 1250 ℃ showed favorable characteristics with a power of 5 W at 150 Ω.