• Proceedings of the KIEE Conference
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• 1987.11a
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• pp.45-48
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• 1987

In applications of step-motor, the requirements of small-size and strong-power gave birth to feed-back drive to the maximum efficiency and complete damping. In this paper, a new scheme that determines switching times from sensed values of position and speed is presented for simple bang-bang type drive circuit. The optimal values of each phase switching times are obtained using conjugate gradient method.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.2 no.2
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• pp.181-186
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• 1998

This paper presents multiplexing structures to provide various subscriber interfaces in an ATM switching system with a high speed internal link, and analyzes the schemes in terms of a mean cell delay and a buffer sin. And we proposed a buffer management strategy to minimize a cell loss and accommodate new ATM transfer capabilities.

• JSTS:Journal of Semiconductor Technology and Science
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• v.8 no.1
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• pp.66-79
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• 2008

Several oxides have recently been reported to have resistance-switching characteristics for nonvolatile memory (NVM) applications. Both binary and ternary oxides demonstrated great potential as resistive-switching memory elements. However, the switching mechanisms have not yet been clearly understood, and the uniformity and reproducibility of devices have not been sufficient for gigabit-NVM applications. The primary requirements for oxides in memory applications are scalability, fast switching speed, good memory retention, a reasonable resistive window, and constant working voltage. In this paper, we discuss several materials that are resistive-switching elements and also focus on their switching mechanisms. We evaluated non-stoichiometric polycrystalline oxides ($Nb_2O_5$, and $ZrO_x$) and subsequently the resistive switching of $Cu_xO$ and heavily Cu-doped $MoO_x$ film for their compatibility with modem transistor-process cycles. Single-crystalline Nb-doped $SrTiO_3$ (NbSTO) was also investigated, and we found a Pt/single-crystal NbSTO Schottky junction had excellent memory characteristics. Epitaxial NbSTO film was grown on an Si substrate using conducting TiN as a buffer layer to introduce single-crystal NbSTO into the CMOS process and preserve its excellent electrical characteristics.

• Journal of Institute of Control, Robotics and Systems
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• v.7 no.4
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• pp.288-294
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• 2001

In this study, a new PWM method considering the actuation delay of high speed solenoid valves is proposed to improve the response characteristics of electro hydraulic servo systems controlled by high speed solenoid valves. In addition, the decision method for the system gain, the basic period of PWM, and the sampling time is proposed, Since the conventional system controlled by high speed solenoid valves is too slow to apply this method, a high speed driving circuit(Quick-Drive) which enables rapid switching of the high speed solenoid valve at a high speed sampling mode is applied to realize this method. The experimental result shows that it is possible to achieve precision and quiet control without occurrence of limit cycle and wide range dead band.

• Proceedings of the Korean Magnestics Society Conference
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• 2008.12a
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• pp.69.2-69.2
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• 2008

• Proceedings of the KIEE Conference
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• 2000.07e
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• pp.66-70
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• 2000

This paper deal with a design and a constant output power control of Zero Current Zero Voltage Switching(ZCZVS) resonant type DC-DC converter by a digital I-PD phase shift controller. When the DC-DC converter for a high density and a high effect control is operated in high speed switching, the switching loss and switching stress of the switching devices are increased. So, the ZCZVS method, which has the phase shift control with the digital I-PD controller, must be use in order to reduce its. And the constant output power voltage that controlled by the digital I-PD controller tracks a reference without steady state error in variable input voltage. The validity of control strategy that proposed is verified experimental results by the Digital Signal Processor TMS320C32.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.2
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• pp.174-180
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• 2008

The pulsed amplifier which switches the main supply voltage of RF amplifier according to input pulse signal has good efficiency and low noise level between pulses. And it has simple structure because it doesn't need a pulse modulator at input port. The pulsed amplifier using the conventional switching circuit has slow fall time compared to rise time. We proposed the novel switching circuit for improving the fall time of pulsed amplifier The proposed switching circuit is implemented by replacing FET of conventional circuit with BJT. As a result of appling this circuit to RF pulsed amplifier, the rise and fall time are 5.7 ns and 21.9 ns at 27 dBm output power, respectively.

• Proceedings of the KIEE Conference
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• 1998.07f
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• pp.2103-2105
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• 1998

Switched Reluctance Motor is simple structure which used Accel/Decel application field because of cheap cost and High efficiency. For driving this motor, it is essential to need position sensor and driving converter. so, many topology and sensor have been studied untill now. Asymmetric Bridge Converter which has been known for the best control and efficiency is used chopping to control current of motor coil according to changing of motor speed. But this is embossed as a fault because it come to bring switching loss due to rapid switching frequency. In this paper, I applied to Soft Switching Mode by Partial Resonant Method to compensate these fault and to show the usabilityness of low switching device.

• Journal of the Optical Society of Korea
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• v.15 no.2
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• pp.161-167
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• 2011

In this paper, we propose an in-plane switching (IPS) mode for liquid crystal displays (LCDs) that, in principle, is free of retardation of the LC cell. Basically, the optical configuration of the LC cell consists of an A-plate and an LC layer for switching between the dark and bright states. We could achieve a fast response time compared with the conventional in-plane LC cell because the free retardation condition of the proposed LC cell enables us to reduce the cell gap even by quarter-wave retardation without any change of the optimized LC material in the transmissive mode. Experiments for verification of the proposed in-plane switching LC cells have shown a significant reduction of the rising time and falling time simultaneously due to the small cell gap. Furthermore, we also proposed an optical configuration for wide viewing property of the retardation free IPS LCD by applying the optical films. We proved the wide-view property of the retardation free IPS LCD by comparing its optical luminance with the calculated optical property of the conventional IPS LCD.

• Journal of Electrical Engineering and Technology
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• v.7 no.2
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• pp.236-239
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• 2012

In this paper, we study the transient characteristics of 4H-SiC DMOSFETs with different interface charges to improve the turn-on rising time. A physics-based two-dimensional mixed device and circuit simulator was used to understand the relationship between the switching characteristics and the physical device structures. As the $SiO_2$/SiC interface charge increases, the current density is reduced and the switching time is increased, which is due primarily to the lowered channel mobility. The result of the switching performance is shown as a function of the gate-to-source capacitance and the channel resistance. The results show that the switching performance of the 4H-SiC DMOSFET is sensitive to the channel resistance that is affected by the interface charge variations, which suggests that it is essential to reduce the interface charge densities in order to improve the switching speed in 4H-SiC DMOSFETs.