• 전력전자학회논문지
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• 제17권3호
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• pp.266-273
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• 2012

In this paper, the new open fault detection and tolerant operation method for 3 phase PWM rectifier is proposed. When open fault occurred on the inverter switches of 3 Phase PWM rectifier, the DC link voltage ripple is increased because the input current of the faulty phase is distorted. In this case, the quality of electric power would decrease, and the life time of DC link capacitor is decreased. The open fault is detected by a simple MRAS(Model Reference Adaptive System) without additional hardware sensors, and the tolerant operation carried out by turning on the opposite switch of the faulty switch without any redundancy. By the proposed method, the faulty phase input current can be controlled, so that 3-phase input current is balanced relatively under the faulty condition and the voltage ripple of DC link output is reduced. The validity of the proposed technique is proved on the 6kW 3-phase PWM rectifier system by simulation and experiment.

• 조명전기설비학회논문지
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• 제28권8호
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• pp.75-81
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• 2014

It has been widely accepted that open phase may separate one of the power lines from power supply which is mainly caused by fuse melting, malfunction for source circuit breaker, contact failure, and disconnection under normal operating conditions, and is considered a kind of failure mode during disconnection of neutral wires as well. When open phase occurs, unequal voltage between phase might happen in the unbalanced load connected each phase, and further, depending on conditions of load, malfunction by providing low voltage. Moreover, load could be burned or overheated with overvoltage, which, in turn, can be a contributor to starting fires. Accordingly, in order to clearly overcome these problems, the current study aims to introduce the theory of uninterruptible power open phase compensation device, meaning that unbalanced power automatically restores balanced power and provides continuously the power supply without blackout, and verify it through simulation and experiments.

• Current Optics and Photonics
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• 제5권2호
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• pp.173-179
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• 2021

The electroluminescence (EL) intensities of GaN-based light-emitting diodes (LEDs) are estimated based on their photoluminescence (PL) properties. The PL intensity obtained under open-circuit conditions is divided into two parts: the PL intensity under a forward bias lower than the optical turn-on voltage, and the difference between the PL intensities under open-circuit conditions and under forward bias. The luminescence induced by photoexcitation under a constant forward bias lower than the optical turn-on voltage is primarily the PL from the excited area of the LED. In contrast the intensity difference, obtained by subtracting the PL intensity under the forward bias from that under open-circuit conditions, contains the EL induced by the photocarriers generated during photoexcitation. In addition, a reverse photocurrent is generated during photoexcitation under constant forward bias across the LED, and can be correlated with the PL-intensity difference. The relationship between the photocurrent and PL-intensity difference matches well the relationship between the injection current and EL intensity of LEDs. The ratio between the photocurrent generated under a bias and the short-circuit current is related to the ratio between the PL-intensity difference and the PL intensity under open-circuit conditions. A relational expression consisting of the ratios, short-circuit current, and PL under open-circuit conditions is proposed to estimate the EL intensity.

• 전력전자학회논문지
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• 제25권4호
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• pp.279-285
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• 2020

An open-end winding (OEW) permanent magnet synchronous motor with dual inverters can synthesize large voltages for a motor with the same DC link voltage. This ability has the advantage of reducing the use of DC/DC boost converters or high voltage batteries. However, zero-sequence voltage (ZSV), which is caused by the difference in the combined voltage between the primary and secondary inverters, can generate a zero-sequence current (ZSC) that increases system losses. Among the methods for eliminating this phenomenon, combining voltage vector eliminated ZSV cannot be accomplished by the conventional Pulse Width Modulation(PWM) method. In this study, a PWM carrier generation method using functionalization to generate a switching pattern to suppress ZSC is proposed and applied to analyze the control influence of the center-zero vector in the switching sequence about the current ripple.

• 한국전기전자재료학회논문지
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• 제23권12호
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• pp.1002-1006
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• 2010

In this study, magnesium (Mg), zinc (Zn) and aluminium (Al) as anode electrode and the solution of NaCl dissolved with 2~20 wt% as electrolytes were used for the metal-air cell. The open circuit voltage, short circuit current and I-V characteristics upon different kinds of anode electrode and electrolyte concentration were investigated. The open circuit voltage, initially about 1.45 V, rises to 1.6 V during the first 10 minutes indicating the necessity of an induction time to activate the catalyst on the air cathode. The short circuit current increases with an increased concentration of NaCl, causes an increase in the conductivity of the electrolyte solution, but the open circuit voltage did not under undergo influence of electrolyte. From NaCl 20 wt% electrolyte, the maximum output power of the magnesium electrode materials was measured with 177mW. It is found that the power characteristics of metal-air cell could be improved by using magnesium electrode materials in the NaCl electrolyte.

• Current Photovoltaic Research
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• 제6권1호
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• pp.12-16
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• 2018

The interest in perovskite solar cells has been skyrocketed owing to their rapid progress in efficiency in recent years. Here, we report the effect of non-stoichiometry in the methylammonium lead trihalide ($MAPbI_3$) precursors used in a solution process with different MAI : $PbI_2$ ratios of 1 : 0.96, 1 : 1.10, 1 : 1.15, and 1:1.20. With an increase in the $PbI_2$ content, the $PbI_2$ secondary phase was found to form at grain boundary region of perovskite thin films, as evidenced by X-ray diffraction (XRD) and scanning electron microscopy (SEM). In terms of device performance, open-circuit voltage in particular is significantly improved with increasing the molar ratio of $PbI_2$, which is possibly ascribed to the reduction in recombination sites at grain boundary of perovskite and hence the prolonged life time of light-generated carriers according to the reported. As a result, the $PbI_2-excess$ devices exhibited a higher power conversion efficiency compared to the MAI-excess ones.

• 대한전자공학회논문지SD
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• 제45권2호
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• pp.34-43
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• 2008

평판 디스플레이 인터페이스를 위한 OpenLDI 수신기 IP를 설계하고, $0.18-{\mu}m$ high-voltage CMOS 공정을 사용하여 프로토타입 칩을 제작하였다. 수신기 회로는 크게 DLL과 parallelizer로 구성된다. DLL은 클록을 재생하고, Parallelizer는 데이터를 병렬화하여 재생된 클록에 정렬한다. 회로의 입력은 한 개의 클록 채널과 네 개의 데이터 채널로 구성된다. 측정을 통해 $10Mhz{\sim}65Mhz$ 범위의 입력주파수에서 클록을 재생하는 것을 확인하였으며, 이는 한 개 채널당 $70Mbps{\sim}455Mbps$의 속도에, 네 개의 데이터 채널을 모두 사용할 시 $280Mbps{\sim}1.82Gbps$의 속도에 해당한다. 상용 LCD 모니터를 개조하여 제작된 칩을 사용한 영상데이터 전송을 실험하였다. 이때의 클록 주파수는 49Mhz, 소모되는 전력은 코어가 19mW, 출력버퍼가 82.5mW로 측정되었다.

• 한국컴퓨터정보학회논문지
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• 제6권4호
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• pp.125-130
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• 2001

이 논문에서는 2개의 OTA를 이용하여 전압제어 이득을 갖는 증폭기의 설계에 대하여 연구하였다. 이를 위하여 먼저 선형동작을 할 수 있는 OTA를 설계하였으며, 설계된OTA 2개를 이용하여 증폭기를 구성하였다. 이 설계에서 OTA는 open-loop로 사용되었다. 컴퓨터 시뮬레이션 결과 설계된 OTA와 증폭기의 특성은 이론 값과 매우 잘 일치하였다. 또한 이 회로는 선형성이 우수하며 저잡음 광대역 증폭기로 동작시킬 수 있다.

• Journal of Power Electronics
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• 제18권5호
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• pp.1585-1594
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• 2018

The estimation of $LiFePO_4$/graphite battery states suffers from the prominent hysteresis phenomenon between the respective open-circuit voltage curves towards charging and discharging. A lot of hysteresis models have been documented to investigate the hysteresis mechanism. This paper reviews and deeply interprets four non-electrochemical hysteresis models and some improvements. These models can be conveniently incorporated into commonly used equivalent circuit models to reproduce battery behaviors. Through simulation and experimental comparisons of voltage predictions and state-of-charge estimations, the pros and cons of these models are presented.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1988년도 추계학술대회 논문집 학회본부
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• pp.172-174
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• 1988

Studies and measurements of open circuit voltage in a metal/insulator/metal structure where metal are electrodes, when the insulator molecules have dipole moments all oriented parallel to each other have been reported here. The measured voltage has been shown to be directed related to the dipole moment of the molecules in the films. The insulator ultra thin films was deposited on them by the Langmuir-Blodgett technique to obtain the structure referred to as z type and Hetero structure of LB films.