• 한국정보디스플레이학회:학술대회논문집
• /
• 2007.08a
• /
• pp.391-394
• /
• 2007

A tristate liquid crystal display characterized by two distinct dark states and one bright state has been presented. These two dark states contribute to two different viewing angles. We demonstrate a single panel of vertically aligned cell whose viewing angles can be directly selected from two sets of driving voltage.

• JSTS:Journal of Semiconductor Technology and Science
• /
• v.11 no.2
• /
• pp.80-87
• /
• 2011

Low temperature hole transport characteristics of gate-all-around p-channel metal oxide semiconductor (PMOS) type silicon nanowire field-effect-transistors with the radius of 5 nm and lengths of 44-46 nm are presented. They show coexisting two single hole states randomly switching between each other. Analysis of Coulomb diamonds of these two switching states reveals a variety of electrostatic effects which is originated by the potential of a single hole captured in the trap near the nanowire.

• Journal of Power Electronics
• /
• v.16 no.6
• /
• pp.2231-2242
• /
• 2016

A simplified model predictive control method is presented in this paper. This method is based on a future reference voltage vector for a three-phase four-leg voltage source inverter (VSI). Compared with the three-leg VSIs, the four-leg VSI increases the possible switching states from 8 to 16 owing to a fourth leg. Among the possible states, this should be considered in the model predictive control method for selecting an optimal state. The increased number of candidate switching states and the corresponding voltage vectors increase the calculation burden. The proposed technique can preselect 5 among the 16 possible voltage vectors produced by the three-phase four-leg voltage source inverters, based on the position of the future reference voltage vector. The discrete-time model of the future reference voltage vector is built to predict the future movement of the load currents, and its position is used to choose five preselected vectors at every sampling period. As a result, the proposed method can reduce calculation load by decreasing the candidate voltage vectors used in the cost function for the four-leg VSIs, while exhibiting the same performance as the conventional method. The effectiveness of the proposed method is demonstrated with simulation and experiment results.

• Journal of Electrical Engineering and Technology
• /
• v.10 no.3
• /
• pp.1066-1074
• /
• 2015

This paper presents the reverse recovery characteristic according to the change of switching states when Si diode and SiC diode are used as clamp diode and proposes a method to minimize the switching loss containing the reverse recovery loss in the neutral-point-clamped inverter at low modulation index. The previous papers introduce many multiple circuits replacing Si diode with SiC diode to reduce the switching loss. In the neutral-point-clamped inverter, the switching loss can be also reduced by replacing device in the clamp diode. However, the switching loss in IGBT is large and the reduced switching loss cannot be still neglected. It is expected that the reverse recovery effect can be infrequent and the switching loss can be considerably reduced by the proposed method. Therefore, it is also possible to operate the inverter at the higher frequency with the better system efficiency and reduce the volume, weight and cost of filters and heatsink. The effectiveness of the proposed method is verified by numerical analysis and experiment results.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2013.02a
• /
• pp.357-358
• /
• 2013

The non-linear characteristics of ON states are important for the application to the high density cross-point memory industry because the sneak current in neighbor cells occurred during reading, erasing, and writing process. Kw of above 20 in ON states, which is the writing current @ Vwrite/the current @ 1/2Vwrite, was required in cross-point ReRAM memory industry. The high current density non-linear IV curve of ZnSe selector was shown and the ALD HfO2 switching device has the linear properties of ON states and the compliance current of 100 uA. To evaluate the performance of the selection device, we connected itto HfO2 switching device in series. The bottom electrode of the selection device was connected to the top electrode of the RRAM. All of the bias was applied with respect to the top electrode of the selection device, whereas the bottom electrode of the RRAM was grounded. In the cross-point application, 1/2Vwrite and -1/2Vwrite were applied to the word-line and bit-line, respectively, which were connected to the selected cell, and a zero bias was applied to the unselected word-lines and bit-lines. The current @ 1/2Vwrite of the unselected cells was blocked by the selection device, thus eliminating the sneak path and obtaining a writing voltage margin. Using this method, the writing voltage margin was analyzed on the basis of the memory size.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2012.08a
• /
• pp.384-384
• /
• 2012

We report nonvolatile memory properties of poly (3, 4-ethylenedioxythiophene) (PEDOT) thin films grown by vapor phase polymerization using FeCl3 as an oxidant. Liquid-bridge-mediated transfer method was employed to remove FeCl3 for generation of pure PEDOT thin films. From the electrical measurement of memory device, we observed voltage induced bipolar resistive switching behavior with ON/OFF ratio of 103 and reproducibility of more than 103 dc sweeping cycles. ON and OFF states were stable up to 104 seconds without significant degradation. Cyclic voltammetry data illustrates resistive switching effect can be attributed to formation and rupture of conducting paths due to oxidation and reduction of PEDOT. The maximum current before reset process was found to be increase linearly with increase in compliance current applied during set process.

• The Transactions of the Korean Institute of Electrical Engineers
• /
• v.45 no.3
• /
• pp.407-414
• /
• 1996

In this paper we consider the variable structure control for a class of discrete-time uncertain multivariable systems where the nominal system is linear. Discrete-time switching dynamics are introduced so that a new type of state trajectories called sliding mode may exist on the sliding surface by state feedback. The quantitative analysis for the matched uncertainties will show that every response of the system with the proposed switching dynamics is bounded within small neighborhoods of the state-space origin. Also, by the similarity transformation it will be shown that the eigenvalues of the closed-loop systems are composed of those of the subsystems which govern the range-space dynamics and null-space dynamics. It will be also shown that ideal sliding mode can be obtained in the absence of uncertainties due to one-step attraction to the sliding surface regardless of initial position of states. (author). 12 refs., 2 figs.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.24 no.9
• /
• pp.710-712
• /
• 2011

In this study, we fabricate resistive switching random access memory (ReRAM) devices constructed with a Al/$HfO_2$/ITO structure on glass substrates and investigate their memory characteristics. The hafnium oxide thin film used as a resistive switching layer is sputtered at room temperature in a sputtering system with a cooling unit. The Al/$HfO_2$/ITO device exhibits bipolar resistive switching characteristics, and the ratio of the high resistance (HRS) to low resistance states (LRS) is more than 60. In addition, the resistance ratio maintains even after $10^4$ seconds.

• Proceedings of the KIPE Conference
• /
• 2008.10a
• /
• pp.137-139
• /
• 2008

A ZVS resonant DC-link inverter using soft switching boost converter is proposed in this paper. The proposed inverter is capable of switching in zero voltage states during the zero-dc-link-voltage period. As a result, the proposed circuit can reduce the switching loss. Operational principles and detailed analysis are presented. Simulation results are also presented to verify the operation principle.

• Proceedings of the KIPE Conference
• /
• 2014.07a
• /
• pp.301-302
• /
• 2014

This paper describes four switch three-phase Z-source rectifier with improved switching characteristics. This configuration has some advantages switching loss and optimal drive circuit. The rectifier has buck-boost function by shoot-through state. Also, the rectifier has the advantage of decreasing inrush current in start-up and transient states. In order to reduce harmonics PWM modulation technique with a variable index has been suggested. Four switch three-phase Z-source rectifier with improved switching characteristics can output stable DC voltage at the same time decreasing the system's harmonic current. And also the paper presents an application of DCC method in Z-source rectifier. Principles and dynamics of the system are discussed in detail. After having viewed the results we can confirm that the proposed method is eligible and efficient.