Earticle

스마트 워치 및 스마트 이어폰과 같은 모바일 기기에 안정된 전원을 공급하기 위하여 정전압 및 정전류 를 통하여 전원을 공급한다. 정전압 및 정전류 제어 IC는 정전압 및 정전류 모드가 필요한 배터리 충전기와 어댑 터에 필요한 IC이다. 제안된 정전압 및 정전류 제어 IC는 기존의 정전압 및 정전류 제어 IC의 전기적 특성을 개 선하고자 한다. 본 논문에서는 정전압 및 정전류 제어 IC를 SOT-26 패키지 형태로 제작하였다. 전기적 특성에서 전압 제어 기준 전위는 5mV, 전체 공급전류는 0.52mA, 전류제어 기준 전위는 1.93V, 단락전류는 13.9mA를 개선 하였다.

Constant voltage and constant current control ICs are necessary ICs for battery chargers and adapters that require constant voltage and constant current modes. The proposed constant voltage and constant current control IC seeks to improve the electrical characteristics of existing constant voltage and constant current control ICs. In this paper, a constant voltage and constant current control IC was manufactured of a SOT-26 package. In electrical characteristics, the voltage control reference potential improved by 5mV, the total supply current by 0.52mA, the current control reference potential by 1.93V, and the short-circuit current by 13.9mA.

This study was performed to identify the effect of constant direct current and to give us methods which can be applied easily in clinic. Six rabbits was used at this experiment. After each animal was fractured at left fibula, divided into experimental group(n=3) and central group(n=3). Experiment duration of electrical stimulation on experimental rabbits was 35 days. Direct current from fifteen microampere to twenty microampere was passed continously through the placed electrode between fracture area and thigh. Negative electrode was placed at fracture area and positive at thigh. Roentgenography was used to observe bone-healing progression wet three times-at 15days, 25days and 35days after electrical stimulation. The results obtained are as followings: 1. Both experimental group and control group do not obtain callus formation on the first roentgenography(15 days after ES). 2. On the second roentgenography(25 days after ES), experimental group achieves above $70\%$ on fracture-healing, but control group achieves about $20-30\%$ on fracture healing. 3. On the third roentgenegraphy(35 nays after ES), experimental group achieves above $85-95\%$ on fracture healing and control group achieves about $60-70\%$ of bone union. Thus, statistically significance(independent t-test) was occured ie the second and third roentgenography between experimental group and control group.

In this paper, it was supposed to current mode design included to required current of ideal LED, through asymptotic method for LED driving. LED`s current characteristic has exponential function, and implementation of driving circuit exists problems. However, it can be designed to linear current source through asymptotic method for ideal required current Proposed LED driving circuits was confirmed the linearity to switched input constant current sources, and driving circuits was designed to satisfy the LED current requirement. Proposed circuit has LSB corresponding to 800μA in 9.6um width and confirmed by Dong-Bu 0.35um CMOS process.

This paper presents an offline current-mode pulse frequency modulation (PFM) controller for low power residential LED lighting, which has a better performance and a simplified structure. A novel controller which contains Constant Current (CC) regulation technique based on auxiliary winding feedback and pulse frequency modulation (PFM) mode basing on the flyback structure is presented, which simplifies the application environment. Also, an input power adjusting technique is introduced which improves the working stability. These techniques are validated by using an integrated circuit designed in 0.5-μm 700V BCD process. In the constant area, when the input AC voltage is from 85V-220V and the load resistance is from 3Ω to 4.7Ω, the test results of actual application circuit show the constant current point is about 1A and the current ripple is about ±4%.

Because the power systemload the randomness of the nature, power transmission of AC induction system has the low efficiency. In order to improve the transmission efficiency，the transmission efficiency influenced factors of the system is analyzed. Based on the current source power transfer system, DC/DC circuit for dynamic adjustment method is proposed. The method ensures that the transmission efficiency is the biggest.

본 논문은 고성능 다결정 실리콘(Poly-Si) 박막 트랜지스터 (Thin Film Transistor)에서 단일 수직 그레인 경계(Single Perpendlcular Grain Boundary)가 고온 캐리어 스트레스(Hot Carrier Stress) 및 정전류 안정성 평가에서 어떠한 효과를 보이는가에 대해서 살펴보았다. 고온 캐리어 스트레스 하에서($V_G=V_{TH}+1V,\;V_D$ =12V),그레이 경계가 없는 다결정 실리콘 TFT와 비교했을 때 그레인 경계를 가지고 있는 다결정 실리를 TFT는 전기 전도(Electric Conduction)에 작용하는 자유 캐리어(Free Carrier)의 개수가 적기 때문에 상대적으로 더욱 우수한 전기적 특성을 나타낸다. 먼저 1000초 동안 고온 캐리어 스트레스를 가해준 결과 단일 그레인 경계를 가진 다결정 실리콘에서의 트랜스 컨덕턴스(Transconductance)의 이동 정도는 5% 미만으로 확인되었다. 반면에 같은 스트레스 조건 하에서 그레인 경계가 존재하지 않는 다결정 실리콘의 경우에는 그 이동 정도가 약 25%에 달하는 것으로 측정되었다. 다음으로 정전류 스트레스(Constant Current Stress) 인가시, 수직형 그레인 경계가 채널 영역 내에 존재하지 않는 다결정 실리콘 TFT는 드레인 접합 부분의 전계 세기를 비교했을 때, 그레인 경계를 가지고 있는 다결정 실리콘 TFT보다 상대적으로 낮은 원 인 때문에 적게 열화되는(Degraded) 특성을 확인할 수 있었다.

Operating conditions significantly affect the durability of polymer electrolyte membrane fuel cells (PEMFC) in marine applications. This study presents experimental results for the performance evaluation of PEMFC single cells under constant voltage and constant current conditions, simulating marine vessel operations. The cells were operated at constant voltages of 0.75 and 0.60 V and at a constant current of 6.64 A. Periodic polarization curve measurements were used to assess performance degradation. The degradation rate at 0.60 V was 13.5% higher than at 0.75 V, while the rate at 0.75 V was 21.0% higher than under constant current conditions at 6.64 A. The findings demonstrate that constant voltage operation accelerates PEMFC degradation more significantly than constant current operation, with the effect being more pronounced at lower voltages. These results provide foundational data for predicting lifespan and determining optimal operating conditions for PEMFCs in marine applications.

In this paper, simple LED driver is proposed. The proposed driver has simple construction having series capacitor, bridge rectifier, and adjustable regulator IC. Constant current control is possible with the use of TL431Z. The proposed in this paper, current is greater than the rating of the load, the current controller device measures the increased current in the circuit, and turned-on so that the current will be shared. Thus current control device makes the circuit more reliable, longevity as well as increase the luminous efficacy of the LED light. The simulation and experimental results are presented to show the validity of the proposed circuits.

Multiple output LED drivers are necessary to achieve better performance and higher reliability in street lighting, tunnel lighting and LCD background lighting applications. Based on LCL-T constant-current characteristics, a modular multiple output LED driver is proposed in this paper. The LCL-T rectifiers are connected to the same voltage bus and work like current sources. However, since there are much higher voltage harmonics in the AC square bus voltage, it is very important to quantitatively analyze how these harmonics influence the precision of the output currents. In addition, all of the switches can achieve Zero Voltage Switching (ZVS) by proper design of the LCL-T network. Finally, a 200-W prototype with five channels is established with an efficiency of 92.25%.

In this paper, we analyze self field effects of Bi-2223 tape-stacked cable assuming constant current density in the cross section of stacked cable. Generally, the critical current of Bi-2223 tape-stacked-cable in much less than the total summation of critical currents of each tape, which is mainly due to the self magnetic fields of the cable itself. Therefore, to predict the critical current of Bi-2223 tape-stacked-cable, we needs to analyze the self filed effects on the stacked cable as well as critical current density data(J$\_$C/) of one tape. To make it more complex, the critical current degradation of Bi-2223 tape is an-isotropic; the critical current is lower in the normal magnetic field(to the tape surface) than in the parallel field. In the paper, a novel approach to predict the critical current of a Bi-2223 tape-stacked-cable from a J$\_$C/-B curve of one tape is presented with the assumption of constant current density across the stacked cable, The approach basically includes the load analysis of the stacked tapes, and its usefulness is confirmed by the experimental data.

A primary-side regulation (PSR) constant current (CC) output and constant voltage (CV) output AC-DC converter is proposed and an adaptive high-precision closed-loop constant current control scheme is put forward in this paper. In the CC mode, the converter adopts the closed-loop control strategy to realize that the switching period adaptively converges to twice the demagnetization time, which realizes the CC output. In addition, exactly detecting the demagnetization time is a prerequisite for obtaining a high-precision output current. Therefore, a demagnetization time detection circuit is designed to provide accurate and reliable demagnetization information. The control IC was fabricated with the Nuvoton 0.5um BCD process, and a 5 V/2 A prototype circuit was implemented to verify its performance. Experimental results show that the CC deviation is within ± 1.4%, which is lower than the target value of ± 2.0%. Under different loads and AC inputs, the conversion efficiency in the CC mode varies between 76.3% and 80.7%.

Power grids are large complicated networks in use around. An absolute phase value for a particular unknown-phase line at a local site should be identified for the operation and management of a 3-phase distribution network. The phase shift for a specific point in the line, as compared with a phase reference point at a substation, must be within a range of ${\pm}60^{\circ}$ for correct identification. However, the phase shift at a particular point can fluctuate depending on the line constants, transformer wiring method, line length, and line amperage, etc. Conducted in this study is a theoretical formulation for the determination of phase at a specific point in the line, Simulink modeling, and analysis for a distribution network. In particular, through evaluating the effects of unbalanced current loads, the limitations of the present phase identification methods are described.

In practical applications, inductive wireless power transfer (IWPT) systems are often required to output a constant voltage or current. However, a change of the load often leads to a change of the output. This paper presents a primary side control method for an IWPT system with the series-none (SN) compensation topology. By using this method, the load, output current, and voltage can be estimated in real time by detecting the output voltage and current of the primary inverter, along with the phase difference between them. This overcomes the disadvantage where the control for a IWPT system requires wireless or wired communication between the primary side and secondary side. Phase shift voltage regulation technology and a PI controller are used to regulate the output voltage or current based on the estimated data. In order to adjust the parameters of the PI controller, a small signal model is established by the generalized state-space averaging (GSSA) method. Finally, simulations and an experimental prototype were established to verify the performance of the primary side control method. The obtained results show that the secondary parameters and variables can be accurately estimated. Under the action of the primary controller, the system can output constant voltage and current values.

The performance of PVA(polyvinyl alchol) is better than another organic dielectric material. Therefore, PVA has been researched for organic and in-organic dielectric material. But research of changing PVA's dielectric constant and leakage current by increasing temperature and concentration was insigificant. We try to find pure PVA and cross-linked PVA's characteristic of dielectric by changing temperature and concentration. 5/10/15wt% PVA concentration (5% interval) was in progress, PVA at $100/150/200/250^{\circ}C$ ($50^{\circ}C$ interval) of experiments was conducted in relation to temperature. The higher the concentration, leakage currents decrease, and dielectric constant is increased. With regard to temperature, we could not see a big change of leakage current and dielectric constant of pure PVA until $200^{\circ}C$. However, we could see a tendency to increase significantly at $250^{\circ}C$. Also, leakage current and dielectric constant of cross-linked PVA gradually increased from at $100^{\circ}C$ to $200^{\circ}C$ and then sharply increased from at $250^{\circ}C$. We tried to find that PVA's inner bonds(hydroxyl group (OH-) lead to the results.

Study of an accurate and robust braking control method is required as a technical improvement to the servo system. In particular, the braker exhibiting constant braking performance under speed variation conditions of the prime mover needs to be investigated. In this paper, the braking torque of the eddy current braker between the electromagnet stator and rotating disk is analyzed. The torque-speed characteristics and accurate disk construction are represented. From the computer simulation results, it was found that eddy current braking torque is linear or approximately constant over the desired speed range depending on the rotor material, disk construction, pole number and pole displacement of the stator. These relations are confirmed by experimental results.

In this paper, a constant current(CC) and constant voltage(CV) control method using a primary-side regulated(PSR) fly-buck converter is proposed. Because the primary-side structure of the fly-buck converter is the same as that of the synchronous buck converter, it always operates in continuous conduction mode(CCM). Therefore, in the proposed method, the load information on the secondary side can always be easily estimated by measuring the primary inductor current at the midpoint of the switch-on period. An accurate CC/CV control can be achieved through simple calculations based on this estimated information. Consequently, the proposed method is advantageous for optimizing the control performance of the PSR converter. The validity of the proposed control was verified using a 5 W prototype of a PSR fly-buck converter. The experimental results confirmed that the current reference of 500 mA was followed within the error range of 1.2%, and that the voltage reference of 12 V was followed within the error range of 1.8% despite the indirect control of the load current and output voltage from the primary side.

A new mixed mode control of constant power and constant current for resistance spot welding inverter is proposed to improve the weld quality. The conventional control scheme adopts constant current or constant power control mode, however, it is not easy to guarantee the high weld quality because of the nonlinear resistance characteristics of the welding point. The proposed method utilizes the nonlinear characteristics by measuring the dynamic resistance in real time. Therefore, it is possible for the welder to be controlled adaptively depending on the welding state. Experimental results show that the proposed control scheme improves the weld quality by 6.8 times compared with the conventional constant current mode control.