• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 2007.04a
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• pp.469-472
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• 2007

최근 많은 광대역 유무선 통신 응용분야에서 OFDM(Orthogonal Frequency Division Multiplexing) 방식을 표준기술로 채택하고 있다 OFDM 방식의 고속 무선 데이터 통신를 위한 FFT 프로세서는 일반적으로 DSP(Digital Signal Processing)로 구현되었으나, 큰 전력 소비를 필요로 한다. OFDM의 단점인 전력문제를 보안하기 위해서 Current-mode FFT LSI가 제안되었다. 본 논문에서는 Current-mode FFT LSI의 구현을 위한 저전력 IVC를 설계하였다. 설계된 IVC는 FFT Block의 출력이 $13.65{\mu}A$ 이상일 때에 3V 이상의 전압을 출력하고, FFT Block의 출력이 $0.15{\mu}A$ 이하일 때에 0.5V 이하의 전압을 출력한다. 그리고 IVC의 총 소모전력은 약 1.65mW이다. $0.35{\mu}A$ 공정에서의 저전력 IVC를 설계함으로서, $0.35{\mu}A$ 공정에서의 Current-mode FFT LSI의 설계가 가능해졌다. 저전력 OFDM 통신용 Current-mode FFT LSI는 무선통신의 발전에 기여할 것으로 전망한다.

• Journal of Satellite, Information and Communications
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• v.8 no.3
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• pp.10-14
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• 2013

In this paper, when applying current-mode circuit design technique showing constant power dissipation none the less operation frequency, to the low power design of dynamic voltage frequency scaling, we introduce the low power current-mode circuit design technique applying MOSFET in sub-threshold region, in order to solve the problem that has large power dissipation especially on the condition of low operating frequency. BSIM 3, was used as a MOSFET model in circuit simulation. From the simulation result, the power dissipation of the current memory circuit with sub-threshold MOSFET showed $18.98{\mu}W$, which means the consumption reduction effect of 98%, compared with $900{\mu}W$ in that with strong inversion. It is confirmed that the proposed circuit design technique will be available in DVFS using a current-mode circuit design.

• The KIPS Transactions:PartA
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• v.15A no.2
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• pp.69-74
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• 2008

This paper proposes a structure of low-power MOS current-mode logic circuit with sleep-transistor to reduce the leakage current. The sleep-transistor is used to high-threshold voltage transistor to minimize the leakage current. The $16\;{\times}\;16$ bit parallel multiplier is designed by the proposed circuit structure. Comparing with the conventional MOS current-model logic circuit, the circuit achieves the reduction of the power consumption in sleep mode by 1/50. This circuit is designed with Samsung $0.35\;{\mu}m$ CMOS process. The validity and effectiveness are verified through the HSPICE simulation.

• Progress in Superconductivity and Cryogenics
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• v.2 no.1
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• pp.31-34
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• 2000

this paper deals with the initial magnetic field decay for a large scale superconducting magnet e.g. NMR/MRI magnet. The high resolution image can not be obained during the periods of the initial field decay. It is known that all superconducting materials have the property of diamagnetism. This diamagnetism is usually explained with the concept of screening current. We assumed that the existence of the screening currebt. we assumed that the existence of the screening current makes the current distribution in the superconducting wire non-uniform. And the initial magnetic field decay is caused steady current state in the view of its pattern. The initial magnetic field decay is caused by the change of the current distribution between the energizing state and persistent current mode. in this paper the theoretical analysis for the current distributions has been introduced for each state. The experiments have been carried out to verify transport currents in order to veperiments, it small at the higher transport current.

• Proceedings of the IEEK Conference
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• 1999.06a
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• pp.986-989
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• 1999

An 12bit current-mode folding and interpolation analog to digital converter (ADC) with multiplied folding amplifiers is proposed in this paper. A current - mode multiplied folding amplifier is employed not only to reduced the number of reference current source, but also to decrease a power dissipation within the ADC. The designed ADC fabricated by a 0.6${\mu}{\textrm}{m}$ n-well CMOS double metal/single poly process. The simulation result shows the power dissipation of 280㎽ with a power supply of 5V.

• The Transactions of the Korean Institute of Power Electronics
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• v.18 no.6
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• pp.579-586
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• 2013

This paper proposes a mode transition algorithm between the grid-tied and the stand-alone operations for the single-phase inverter with the energy storage system. For the grid-tied operation, the dc-link voltage and the output current are required to be control. For the stand-alone mode, both the output voltage and the output current should be regulated. In order to mitigate a falling-off in control performance during transients in mode change, the load power estimation and the current selection schemes are proposed. The proposed method allows an optimized current reference is selected to reduce an output voltage drop and an excessive over-current in transient. To verify the effectiveness of the proposed method, both the simulation and the experiments for a 3kW single-phase inverter with the energy storage system have been conducted. From the results, it has been confirmed that the proposed method reduces a transient error as well as implementing smooth mode transition.

• 제어로봇시스템학회:학술대회논문집
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• 2004.08a
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• pp.488-492
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• 2004

In this paper, the design of a speed sensorless vector control system for induction motor is performed by using a new sliding mode technique based on current model flux observer. A current and flux observer based on the current estimation error is constructed. The proposed current observer includes a sliding mode function, which is derivative of the flux. That is, sliding mode observer which allows the estimation of both the rotor speed and flux based on the measurement of motor terminal quantities, would be proposed. And, a synergetic speed controller using the estimated speed signal is designed to stabilize the speed loop. Simulation results are presented to confirm the theoretical analysis, and to show the system performance with different observer gains and the influence of the motor parameter.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.62 no.2
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• pp.84-89
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• 2013

In this paper, we propose interface circuits for reducing power consumption and EMI when sequences of data from LCD controller to LCD driver IC by transmitting two bit data during one clock period. The proposed circuits are operated in current mode, which is different from conventional voltage-mode signaling techniques, and also employ threshold technique of Modified-LVDS(Low Voltage Differential Signaling) method. We have simulated the proposed circuits using H-SPICE tool for performance analysis of the proposed method. The simulation results show that the proposed circuits provide a faster transmission speed and stronger noise immunity than the conventional LVDS circuits. It might be suitable for the real-time transmission of huge image data in LCD system.

• Journal of Welding and Joining
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• v.15 no.1
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• pp.109-115
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• 1997

The arc stability and the metal transfer mode of high deposition GMA welding were investigated using various compositions of shielding gas with two types of filler, ie solid wire and metal cored wire. As for a solid wire, the transfer mode changed from axial spray to rotational spray with increasing wire feed rate (welding current) and the transition current was different with the gas composition. The gas composition also affected the apparent stability of rotating arc. As for a metal cored wire, on the other hand, no transition occurred and thus spray transfer mode could be applied with the welding current over 500A (deposition rate over 300g/min). Looking for the development of high deposition GMA welding process, above results were discussed in two different ways, one is to elevate the transition current, the other is to stabilize the rotational transfer mode.

• Journal of Electrical Engineering and Technology
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• v.6 no.5
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• pp.647-657
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• 2011

The present paper proposes a sliding mode control with fixed switching frequency for three-phase three-leg voltage source inverter based four-wire shunt active power filter. The aim is to improve phase current waveform, neutral current mitigation, and reactive power compensation in electric power distribution system. The performed sliding mode for active filter current control is formulated using elementary differential geometry. The discrete control vector is deduced from the sliding surface accessibility using the Lyapunov stability. The problem of the switching frequency is addressed by considering hysteresis comparators for the switched signals generation. Through this method, a variable hysteresis band has been established as a function of the sliding mode equivalent control and a predefined switching frequency in order to keep this band constant. The proposed control has been verified with computer simulation which showed satisfactory results.