• Proceedings of the KIPE Conference
• /
• 1998.10a
• /
• pp.346-351
• /
• 1998

In design of a digital current controller for a 3-phase (3 ) voltage-source (VS) PWM converter, its conventional model, i.e., stationary or synchronous reference frame model, is used in obtaining its discretized version. It introduces, however, inherent errors since the following practical problems are not taken into consideration: the characteristics of the space vector-based pulse-width modulation (SVPWM) and the time delays in the process of sampling and computation. In this paper, the new hybrid reference frame model of the 3 VS PWM converter is proposed considering these problems. In addition, the direct digital current controller based on this model is designed without any prediction or extrapolation algorithm to compensate the time delay. So the control algorithm is made very simple. It represents no steady-state error in input current control and has the optimized transient responses. The validity of the proposed algorithm is proved by the computer simulation and experimental results.

• Journal of Sensor Science and Technology
• /
• v.32 no.2
• /
• pp.100-104
• /
• 2023

In this study, a device was fabricated to check the possibility of a memory device by controlling the oxygen functional groups in graphene oxide formed with a 45-second exposure time. We discovered that graphene oxide can be formed using the ultraviolet (UV) light treatment method with different exposure times. Moreover, Raman spectroscopy measurement revealed that the oxygen functional groups can be moved by controlling the voltage. We further studied the change in the local graphene oxide region, which was found to be related to the modulation of the electrical properties of the device. Therefore, the fabricated graphene oxide device can be used as a wettability switching membrane and graphene-based ion transport device.

• Proceedings of the KIPE Conference
• /
• 2020.08a
• /
• pp.259-260
• /
• 2020

모듈화 멀티레벨 컨버터 (modular multilevel converter, MMC)는 고압직류송전(high-voltage direct current, HVDC)에 대한 기술이 발전함에 따라서 이와 관련된 전력변환 장치로써 많은 연구되어지고 있다. 10kV 이하로 구현되는 중압직류송전(medium-volatge direct current, MVDC) 시스템 및 모터 드라이브에 이용되는 MMC의 경우에는 수백 개의 직렬 서브모듈로 구성된 MMC가 사용되는 HVDC와 다르기 때문에 여러 모듈레이션 방식에서의 다른 장단점을 가지게 된다. 본 논문에서는 전력전자 시뮬레이션 툴인 PSIM을 이용하여 여러가지 모듈레이션의 MVDC으로의 적용에 있어서의 장단점을 분석한다.

• Journal of Ginseng Research
• /
• v.27 no.3
• /
• pp.120-128
• /
• 2003

Alternative medicines such as herbal products are increasingly being used for preventive and therapeutic purposes. Ginseng is the best known and most popular herbal medicine used worldwide. In spite of some beneficial effects of ginseng on the nervous system, little scientific evidence shows at the cellular level. In the present study, I have examined the direct modulation of ginseng total saponins and individual ginsenosides on the activation of $Ca^{2+}$ channels and NMDA-gated channels in cultured rat dorsal root ganglion (DRG) and hippocampal neurons, respectively. In DRG neurons, application of ginseng total saponins suppressed high-voltage-activated $Ca^{2+}$ channel currents and ginsenoside Rg$_3$, among the 11 ginsenosides tested, produced the strongest inhibition on $Ca^{2+}$ channel currents. Occlusion experiments using selective $Ca^{2+}$ channel blockers revealed that ginsenoside Rg$_3$ could modulate L-, N-, and P/Q-type currents. In addition, ginsenoside Rg$_3$ also proved to be an active component of ginseng actions on NMDA receptors in cultured hippocampal neurons. Application of ginsenoside Rg$_3$ suppressed NMDA-induced [Ca$^{2+}$]$_{i}$ increase and -gated channels using fura-2-based digital imaging and patch-clamp techniques, respectively. These results suggest that the modulation of $Ca^{2+}$ channels and NMDA receptors by ginsenoside Rg$_3$ could be part of the pharmacological basis of ginseng actions in the peripheral and central nervous systems.ous systems.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.35 no.12C
• /
• pp.965-970
• /
• 2010

In the NAND flash memory storing two bits per cell, data is discriminated among four levels of electrical charges. We refer to these four levels as E, P1, P2, and P3 from the low voltage. In the statistics, many errors occur when E and P3 are stored at the next cells. Therefore, we propose a coding scheme for avoiding E-P3 or P3-E data patterns. We investigate two modulation codes for 9/10 code (9 bit input and 5 symbol codeword) and 11/12 code (11 bit input and 6 symbol codeword).

• The Transactions of the Korean Institute of Power Electronics
• /
• v.4 no.5
• /
• pp.462-473
• /
• 1999

This paper addresses the current measurement issue of all digital field oriented control of ac motors. The p paper focuses on the effect of low-pass filter and also on the sampling of the fundamental component of the m motor current. The low-pass filter, which suppresses the switching noise of the motor current, introduces v variable phase delay according to the current ripple frequency. It is shown that the current sampling error c consists of the fundamental component and high frL'quency ripple components. In this paper, the dependency of t this current sampling e$\pi$or on the reference voltage vector is investigated analytically and a sampling technique i is proposed to minimize the error. The work is based on the three phase symmetry pulse width modulation l inverter driving an induction machine. With this technique, the bandwidth of current regulator can be extended t to the limit given by the switching frequency of the inverter and more precise torque regulation is possible.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.9 no.6
• /
• pp.525-535
• /
• 2004

In this paper, a two-phase DZRCD(Dual Zero Vector Modes RCD) technique is proposed to develope the problem of a conventional two-phase RCD-PWM (Random Centered Distribution PWM) which gives the power spectra of narrow band range in the high modulation index (M). In the proposed DZRCD technique, the zero vector $V_0$ is selected as $V_0$(111) for M$\geqq$0.8. Also, $V_0$ is selected as $V_0$(000) for the modulation indices < 0.8. For the unplementation of the proposed method, a 16-bit micro-controller Cl67 was used and the experiments were conducted with the 1.5kw induction motor under no load condition. The experimental results show that the voltage / current spectra is spread to a wide band range, and the switching noise of motor is reduced by the proposed method compared to the conventional random operation.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.8 no.2
• /
• pp.151-164
• /
• 2003

In this paper, induction motor drives with low switching acoustic noise based on the 2 phase modulated RLL(Random Lead-Lag) PWM is proposed and implemented. The proposed switching method is much bettor than 3 phase modulated RLL-PWM from the standpoint of the broadening effect of the acoustic noise spectrum. Along with the randomization of PWM Pulses, SVM(Space Vector Modulation) is executed in the TMS320C31 DSP(Digital Signal Processor). To verify the validity of the proposed RPWM(Random PWM), the experimental study was tried. The experimental results show that the performance of the proposed method and the 3 phase center-aligned SVM / conventional RLL-PWM are nearly the same from the viewpoint of the constant v/f centrel. But, in case of the proposed 2 phase modulated RLL-PWM, the spectrum characteristics of the voltage and the switching acoustic noise are shown to have better broadening effect than 3 phase modulated one.

• Journal of the Institute of Electronics Engineers of Korea SD
• /
• v.38 no.3
• /
• pp.211-219
• /
• 2001

This paper describes a read-only CMOS transponder IC for RFID applications. A full-wave rectifier implemented using NMOS transistors supplies the transponder with a dc supply voltage using the magnetic field generated from a reader. A 64-bit ROM has been designed for a data memory. Front-end impedance modulation and Manchester coding are used for transmitting the data from the transponder memory to the reader. A new damping circuit which has almost constant damping rate under the variations of the distance between the transponder and the reader has been employed for impedance modulation. The designed circuit has been fabricated using a 0.65${\mu}{\textrm}{m}$2-poly, 2-metal CMOS process. Die area is 0.9mm$\times$0.4mm. Measurement results show that it has a constant damping rate of around 20~25% and a data transmission rate of 3.9kbps at a 125KHz RF carrier. The power required for reading operation is about 100㎼. The measured reading distance is around 7cm.

• Journal of the Institute of Electronics Engineers of Korea SD
• /
• v.43 no.11 s.353
• /
• pp.14-18
• /
• 2006

Optical interferometer is used for various optical measurement fields in optical metrology and biomedical measurements. In an optical interferometer, optical delay line has to change the optical path length of a reference arm to match with that of a sample in and it's speed was limited by reference arm movement speed. In this paper, we proposed an all-fibered RSODRapid Scanning-speed Optical Delay) without any mechanical movement, and we applied this system to optical interferometer. Experimental setup is consist of pulse laser source (center wavelength 1304nm, pulse width 30ps, repetition rate 10GHz), two phase modulators and dispersive shifted fiber. As experimental results, we obtain the maximum time delay of 11ps at 10MHz repetition rate, and it is easily tuneable the time delay by modulation frequency and modulation voltage.