• The Transactions of the Korean Institute of Power Electronics
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• v.18 no.2
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• pp.192-198
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• 2013

The rapidly growing demand for electric power systems in electric vehicles (EVs) and hybrid electric vehicles (HEVs) require simpler, cost-effective, and higher performance components. In this paper, a novel power conversion system for hybrid electric vehicles is proposed for these needs. The proposed power conversion system reduces the conversion system cost while preserving same functionality. The proposed power conversion system can boost multi-sources to drive a traction motor and to store energy at the same time reducing number of switching components. In this paper, all operational modes of the proposed converter are explained in detail and verified by a computer simulation first. Then, the topology and operational modes are experimentally verified. Based on the results, the feasibility of the proposed multi-mode single leg power conversion system for EV and HEV applications is discussed.

• 한국정보디스플레이학회:학술대회논문집
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• 2003.07a
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• pp.664-667
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• 2003

Super In Plane Switching (S-IPS) technology is applied for large TFT-LCD panels used in TV applications. It has a lot of advantages in comparison to the alternative, VA technology. S-IPS shows excellent viewing angle properties and fast response time between intermediate gray levels. If the performance parameters which describe the actual visual performance are considered, S-IPS is much more advantageous.$^{1)}$ However, it shows relatively low contrast ratio in diagonal direction compared to viewing angle characteristic in upper/down direction in S-IPS. In order to compensate the relatively low diagonal contrast ratio, a newly designed optical film was applied and the truly wide view angle of a S-IPS TW(True Wide)-IPS) was achieved. Our newly developed 30-inch TFT-LCD panel reveals TW-IPS that is optimized for TV application

• Proceedings of the KIEE Conference
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• 1989.07a
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• pp.567-570
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• 1989

A constant V/F control system of voltage contrlled PWM inverter has a unstable operation of the low- speed and the light-load. In this paper, the authors propose stability control with idealized operation of induction motor by the neglect of primary leakage inductance and resistance. Also ldealized operation system is adopted voltage error, feed back impedance circuit, and increasing resistance from dead time of switching is compensated by the soft ware with u-processors. The proposed simulation of the idealized control method is proved at the low-speed operation for three phase induction motor.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.54 no.1
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• pp.1-8
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• 2005

This paper presents a characteristic analysis of switched reluctance motor (SRM) considering switching control method and DC link voltage ripple by using time-stepped voltage source finite element method in which the magnetic field is combined with drive circuit. We also examine the influence of freewheeling diodes and DC link voltage ripple on the performance of the SRM such as torque ripples and radial force on the surface of the teeth. The freewheeling diodes and DC link voltage ripples must be taken into account to predict the performance of SRM.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.54 no.4
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• pp.171-178
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• 2005

The proposed dual-output DC-DC converter that bases on flyback converter can obtain two output voltage with non-isolated main-output and isolated sub-output at the same time using single-winding high frequency transformer. It can solve problems in multi-winding converter that use one main-switch, and also control quality of isolated sub-output voltage can be improved by additional sub-switch to the second. For analysis and design of the proposed converter system, converters are classified as operation mode from switching state and are become modeling by applying state space averaging method. Steady-state characteristics and dynamic characteristics are analyzed by DC component and perturbation component from state space averaging model. From experiment converter, validity of analysis and design for the propose converter system is confirm.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.49 no.2
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• pp.123-129
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• 2000

This paper proposes a novel current control method of three-phase PWM rectifiers using estimated currents without phase current sensors. The phase currents are reconstructed from switching states of the rectifier and the measured dc output currents. To eliminate the calculation time delay effect of the microprosessor, the current at the next sampling instant are predicted by a predictive state observer and then are used for feedback control. Experimental results show that the control performance of the proposed system is almost the same as that of the phase current sensor-based system.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.55 no.4
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• pp.224-230
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• 2006

The conventional way to implement a bidirectional converter with boost/buck has been to use two general purpose PWM ICs with a single supply voltage. In this case, when one direction mode is in operation, the other is disabled and the output of the error amplifier of the disabled IC may be saturated to a maximum value or zero. Therefore, during mode transition, a circuit which can disable the switching operation for a certain time interval is required making it impossible to get a seamless transition. In this paper, the limitations of the conventional 42V/14V bi-directional DC/DC converter implemented with general current mode PWM ICs with a single supply voltage are reviewed and a new current mode PWM controller circuit with a dual voltage system is proposed. The validity of the proposed circuit is investigated through simulation. and experiments.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.19 no.1
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• pp.81-86
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• 2006

We have studied electrode-optic characteristics of in-plane switching (IPS) of liquid crystal director driven by an oblique electric field. Because the conventional IPS mode does not have an electrode on top substrate, it shows not only slow response time due to weak electric field but also slow discharging problem when electrostatic field is generated after fabricating the cell. To solve these problems, we have formed additional electrode including dielectric layer in the inner part of the cell on top substrate and studied electrode-optic characteristics of the new device.

• Electrical & Electronic Materials
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• v.7 no.2
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• pp.152-156
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• 1994

The rapid thermal annealing effects of Sol-Gel derived ferroelectric PZT thin films were investigated. It was found that rapid thermal annealing(RTA) of spin coated thin films on silicon typically >$800^{\circ}C$ for about 1 min. was changed to the perovskite phase. Rapid thermally annealed films recorded maximum remanent polarization of about 5 .mu.C/cm$^{2}$, coercive field of around 30kV/cm. The switching time for polarization reversal was about 220ns. The films of RTA process showed smooth surface, and high breakdown voltages of over 1 MV/cm and resistivity of $1{\times}{10^12}$ .ohm.cm at 1 MV/cm. It was verified that the polarization reversal of the PZT film was varied partially with applying the multiple short pulse.

• Proceedings of the KIEE Conference
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• 2000.07e
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• pp.79-84
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• 2000

This paper presents an implementation of digital position control system for an induction motor vector drives by a direct torque control(DTC) using the 16bit DSP TMS320 F240. The DSP controller enable enhanced real time algorithm and cost-effective design of intelligent controller for motors which can be yield enhanced operation, fewer system components, lower system cost, increased efficiency and high performance. The system presented are stator flux and torque observer using current model that inputs are current sensing of motor terminal and rotor angle for a low speed operating area, two hysteresis controller, optimal switching look-up table, and IGBT voltage source inverter by fully integrated control software. The developed control system are shown a good motion control response characteristic results and high performance features using 2.2Kw general purposed induction motor.