• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제55권4호
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• pp.231-237
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• 2006

This paper proposes an effective drive of high intensity discharge (HID) lamp ballast for cars. All control functions of the proposed ballast are implemented using a low-cost single chip microcontroller, PIC16C73 to optimize the total system size and to minimize cost through minimization of total component number. The proposed ballast generates high open-circuit voltage to ignite the lamp and is controlled to supply effectively the power required to shorten warm-up period after the breakdown. The DC-DC converter of the DC-AC converter part of the ballast utilizes the flyback converter topology that can minimize component number. Also, because to more minimize the ballast size, the transformer size must be minimized, for this, PWM (Pulse Width Modulation) pulses are generated with high frequency using the PWM module of the microcontroller. An analysis for this is explained, briefly. As if the operation of the lamp and ballast arrives at steady-state, then the ballast must AC-control the lamp, for this, the microcontroller utilizes the other PWM module. And the part related to the igniter is explained, briefly. It is shown through experimental results that the controller of the proposed ballast has good performance for the HID lamp for cars.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 하계학술대회 논문집 F
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• pp.2668-2670
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• 1999

In the past, the PWM converter had a large switching loss by hard switching and difficult to high frequency operation. The resonance converter to decrease the switching loss and EMI is required the frequency control and needed to reduce the voltage or current stress at each parts. So, this paper propose the 3-phase boost converter and the method to compensated input power factor by control the amplitude - an instantaneous value of the DC inductor current -and control the switching frequency that a modulation error by the ripple of the DC inductor current. The proposed 3-phase PWM boost converter of single phase control type can takes higher capacity and compensate the power factor by using Feed back controller at each phase for the existing 3-phase bridge rectifier type. Moreover the 3-phase full bridge type using the rectifier at each 3-phase circuit will be small size reactor and compensate input power factor by minimize harmonic components of each phase.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2004년도 추계학술대회 논문집 Vol.17
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• pp.57-60
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• 2004

This paper presents multibit Sigma-Delta ADC using Leslie-Singh Structure to Improve nonlinearity of feedback loop. 4-bit flash ADC for multibit Quantization in Sigma Delta modulator offers the following advantages such as lower quantization noise, more accurate white-noise level and more stability over single quantization. For the feedback paths consisting of DAC, the DAC element should have a high matching requirement in order to maintain the linearity performance which can be obtained by the modulator with a multibit quantizer. Thus a Sigma-Delta ADC usually adds the dynamic element matching digital circuit within feedback loop. It occurs complexity of Sigma-Delta Circuit and increase of power dissipation. In this paper using the Leslie-Singh Structure for improving nonliearity of ADC. This structure operate at low oversampling ratio but is difficult to achieve high resolution. So in this paper propose improving loop filter for single-bit feedback multi-bit quantization Sigma-Delta ADC. It obtained 94.3dB signal to noise ratio over 615kHz bandwidth, and 62mW power dissipation at a sampling frequency of 19.6MHz. This Sigma Delta ADC is fabricated in 0.25um CMOS technology with 2.5V supply voltage.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2004년도 하계학술대회 논문집 Vol.5 No.2
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• pp.1222-1225
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• 2004

This paper presents multibit Sigma-Delta ADC using noise-shaped dynamic element matching(DEM). 5-bit flash ADC for multibit quantization in Sigma Delta modulator offers the following advantages such as lower quantization noise, more accurate white-noise level and more stability over single quantization. For the feedback paths consisting of DAC, the DAC element should have a high matching requirement in order to maintain the linearity performance which can be obtained by the modulator with a multibit quantizer. The DEM algorithm is implemented in such a way as to minimize additional delay within the feedback loop of the modulator Using this algorithm, distortion spectra from DAC linearity errors are shaped. Sigma Delta ADC achieves 82dB signal to noise ratio over 615H7z bandwidth, and 62mW power dissipation at a sampling frequency of 19.6MHz. This Sigma Delta ADC is designed to use 0.25um CMOS technology with 2.5V supply voltage and verified by HSPICE simulation.

• 전자공학회논문지A
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• 제32A권6호
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• pp.41-50
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• 1995

A state-of-the-arts GaAs power metal semiconductor field effect transistor (MESFET) for 3.3V operation digital hand-held phone at 900 MHz has been developed for the first time, The FET was fabricated using a low-high doped structures grown by molecular beam epitaxy (MBE). The fabricated MESFETs with a gate width of 16 mm and a gate length of 0.8 .mu.m shows a saturated drain current (Idss) of 4.2A and a transconductance (Gm) of around 1700mS at a gate bias of -2.1V, corresponding to 10% Idss. The gate-to-drain breakdown voltage is measured to be 28 V. The rf characteristics of the MESFET tested at a drain bias of 3.3 V and a frequencyof 900 MHz are the output power of 32.3 dBm, the power added efficiency of 68%, and the third-ordr intercept point of 49.5 dBm. The power MESFET developed in this work is expected to be useful as a power amplifying device for digital hand-held phone because the high linear gain can deliver a high power added efficiency in the linear operation region of output power and the high third-order intercept point can reduce the third-order inter modulation.

• 전자공학회논문지
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• 제50권10호
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• pp.98-104
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• 2013

본 논문에서는 무선 통신 및 근거리 위치 인식이 가능한 WBAN(wireless body area network) 용 UWB(Ultra-wide band) 수신기 회로를 제안한다. UWB 수신기는 에너지 검출 방식의 OOK(on-off keying) 변조가 가능하도록 설계가 되었다. 고속의 sampling 을 하기 위해서 4bit ADC 는 DLL(delay locked loop) 을 이용하여 sub-sampling 기법을 사용하도록 설계되었다. 제안된 UWB 수신기는 CMOS $0.18{\mu}m$ 공정을 이용하여 설계되었으며, 전원 전압 1.8V에서 61mA의 전류를 소모하면서 -85.7dBm의 수신 감도, 42.1dB의 RF front-end 게인, 3.88 dB의 noise figure, 최대 4m 까지의 거리 감지 성능을 가지고 있다.

• Journal of Magnetics
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• 제17권1호
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• pp.42-45
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• 2012

We have developed an alternating magnetic field stimulation system consisting of a switched-mode power supply and a digital control circuit which modulates a duty ratio to maintain a magnetic field intensity of a few mT even while the frequency increases up to 4 kHz with a controllable coil temperature below $30^{\circ}C$ in air. This duty ratio modulation and water circulation are advantageous for cell culture under ac-magnetic field stimulation by preventing the incubator from exceeding a cell-viable temperature of $37^{\circ}C$. Although the temperature of the coil when subjected to a sinusoidal voltage rapidly increased, that of our system modulated by the duty factor did not change. This is a potentially valuable method to investigate the effects of intermediate frequency magnetic field stimulation on biological entities such as cells, tissues and organs.

• Tribology and Lubricants
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• 제29권4호
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• pp.213-217
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• 2013

As commercial atomic force microscopy (AFM) probes made of Si and $Si_3N_4$ have low stiffness, it is difficult to induce sufficient elastic deformation on the surface of a specimen in a tapping mode. Therefore, high-guality phase contrast images can not obtained. On the other hand, a tungsten AFM probe has relatively higher stiffness than a commercial AFM probe. Accordingly, it is expected to provide an enhanced phase contrast image, which is an effective tool for achieving a better understanding of the micromechanical properties of worn surfaces and wear mechanisms. In this study, on electrochemical etching method was optimized to fabricate tungsten probe tips for an AFM. Electrochemical etching was performed by applying pulse waves with a 20% duty cycle at various voltages instead of only a DC voltage, which has been commonly used.

• Progress in Superconductivity
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• 제11권2호
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• pp.118-122
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• 2010

Electrical transport properties were measured on $SmFeAsO_{0.85}$ single crystals along the c-axis for various temperatures and magnetic fields. For the measurements a mesa structure was fabricated on the surface of the single crystals. Samples showed a metallic temperature dependence of resistance and current-voltage curves without hysteretic multiple branch splitting that is usually observed in tunneling Josephson junctions. In addition, in ab-planar magnetic fields, samples did not show the Fraunhofer-type field modulation of the critical current. All these features indicate that the c-axis transport characteristics of $SmFeAsO_{0.85}$ single crystals are explained by the anisotropic bulk superconductivity rather than Josephson tunneling.

• JSTS:Journal of Semiconductor Technology and Science
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• 제6권2호
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• pp.106-113
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• 2006

Electrical properties of $Si_{0.88}Ge_{0.12}(C)$ p-MOSFETs have been exploited in an effort to investigate $Si_{0.88}Ge_{0.12}(C)$ channel structures designed especially to suppress diffusion of dopants during epitaxial growth and subsequent fabrication processes. The incorporation of 0.1 percent of carbon in $Si_{0.88}Ge_{0.12}$ channel layer could accomodate stress due to lattice mismatch and adjust bandgap energy slightly, but resulted in deteriorated current-voltage properties in a broad range of operation conditions with depressed gain, high subthreshold current level and many weak breakdown electric field in gateoxide. $Si_{0.88}Ge_{0.12}(C)$ channel structures with boron delta-doping represented increased conductance and feasible use of modulation doped device of $Si_{0.88}Ge_{0.12}(C)$ heterostructures.