• 한국재료학회지
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• 제30권7호
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• pp.327-332
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• 2020

Laser induced surface activation (LISA) technology requires refined selection of process variables to fabricate conductive microcircuits on a general polymer material. Among the process variables, laser mode is one of the crucial factors to make a reliable conductor pattern. Here we compare the continuous wave (CW) laser mode with the pulse wave (PW) laser mode through determination of the surface roughness and circuit accuracy. In the CW laser mode, the surface roughness is pronounced during the implementation of the conductive circuit, which results in uneven plating. In the PW laser mode, the surface is relatively smooth and uniform, and the formed conductive circuit layer has few defects with excellent adhesion to the polymer material. As a result of a change of laser mode from CW to PW, the value of Ra of the polymer material decreases from 0.6 ㎛ to 0.2 ㎛; the value of Ra after the plating process decreases from 0.8 ㎛ to 0.4 ㎛, and a tight bonding force between the polymer source material and the conductive copper plating layer is achieved. In conclusion, this study shows that the PW laser process yields an excellent conductive circuit on a polymeric material.

• 한국재료학회지
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• 제10권3호
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• pp.212-217
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• 2000

일반적으로 TFT(thin film transistor)의 유전체막으로 실리콘 질화막($Si_3$$N_4$)이나 실리콘 산화막(SiO$_2$)을 $200-300^{\circ}C$의 온도에서 증착을 하게 되는데 본 연구에서는 비정질 실리콘과 유전체막 사이의 계면 특성 특히 계면의 거칠기를 향상시키기 위해서 기존의 증착법이 아니라 비정질 실리콘(a-Si:H)과 산소 ECR 플라즈마의 반응에 의한 산화 막의 성장법을 시도했는데, 이때 기판은 의도적으로 가열하지 않았으며 특히 본 연구에서는 기존의 시도와는 달리 ECR 플라즈마를 형성할 때 마이크로파 전력에 pulse를 가하는 방법을 최초로 시도했고, 계면에 불순물의 혼입을 최대한으로 줄이기 위해서 진공을 파괴하지 않은 상태로 산화막을 연속적으로 성장시키는 방법을 이용했다. Pulse를 가했을 경우에는 pulse를 가하지 않은 경우에 비해서 화학양론적 측면, 유전상수, 산화막의 표면 평탄도 등에서 우수한 산화막이 성장했으며, 특히 비정질 실리콘과 유전체막 사이의 계면 특성을 반영하는 산화막의 표면 평탄도가 1/3정도로 획기적으로 줄어들었다.

• 전기학회논문지
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• 제65권9호
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• pp.1597-1604
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• 2016

The speed at which the SRM (Switched Reluctance Motor) makes a transition from chopping control to single pulse operation. (i.e., low speed to high speed operation). It is unsatisfied with performance at all operational regimes. In this paper, the operational performance of SRM can be improved by using current hysteresis control method. This method maintains a generally flat current waveform. At the high speed, the current chopping capability is lost due to the development of the back-EMF. Therefore SRM operates in single pulse mode. By using zero-current switching and zero-voltage switching technique, the stress of power switches can be reduce in chopping mode. When the commutation from one phase winding to another phase winding, the current can be zero as fast as possible in this period because several times negative voltage of DC-source voltage produce in phase winding. This paper is compared to performance based on energy efficient C-dump converter topology and the proposed resonant C-dump converter topology. Simulation and experimental results are presented to verify the effectiveness of the proposed circuit.

• 한국통신학회논문지
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• 제19권3호
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• pp.533-542
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• 1994

가상용 도플러 레이다의 경우 기상이변 등을 탐지하기위해서는 대상지역의 강우량, 풍속의 변화, turbulence정도 등을 거리 및 방위각별로 세밀하게 측정, 표시하여줄 수 있어야 한다. 이러한 목적으로 쓰여지고 있는 알고리즘으로 pulse pair추정방법이 가장 효율적인 것으로 인정되어지고 있다. 그러나 이 방법은 레이다 반사신호의 스펙트럼이 비대칭일 경우 bias오차가 크게 생길 수 있으며 두개이상의 peak 점을 갖는 스펙트럼의 경우에는 무의미한 결과가 얻어질 수 있다. 따라서 본 논문에서는 이와 같은 bias 오차에 대해서 분석하였으며 이러한 오차를 줄이기 위한 개선된 방법을 제시하였다. 또한 여러개의 peak점을 갖는 스펙트럼이나 비대칭의 정도가 심할 경우 mode 추정 방법을 이용한 탐지 기법에 대해서도 연구, 검토되어졌다.

• ETRI Journal
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• 제39권2호
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• pp.292-299
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• 2017

We propose pulse-mode dynamic $R_on$ measurement as a method for analyzing the effect of stress on large-scale high-power AlGaN/GaN HFETs. The measurements were carried out under the soft-switching condition (zero-voltage switching) and aimed to minimize the self-heating problem that exists with the conventional hard-switching measurement. The dynamic $R_on$ of the fabricated AlGaN/GaN MIS-HFETs was measured under different stabilization time conditions. To do so, the drain-gate bias is set to zero after applying the off-state stress. As the stabilization time increased from $ 0.1{\mu}s$ to 100 ms, the dynamic $R_on$ decreased from $160\Omega$ to $2\Omega$. This method will be useful in developing high-performance GaN power FETs suitable for use in high-efficiency converter/inverter topology design.

• 조명전기설비학회논문지
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• 제21권4호
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• pp.19-27
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• 2007

This paper presents a novel soft-switching PWM utility frequency AC to high frequency AC power conversion circuit incorporating boost H-bridge inverter topology, which is more suitable and acceptable for cost effective consumer induction heating applications. The operating principle and the operation modes are presented using the switch mode equivalent circuits and the operating voltage and current waveforms. The performances of this high-frequency inverter using the latest IGBTs are illustrated, which includes high frequency power regulation and actual efficiency characteristics based on zero voltage soft-switching(ZVS) operation ranges, and the power dissipation as compared with those of the conventional type high frequency inverter. In addition, a dual mode control scheme of this high frequency inverter based on asymmetrical pulse width modulation(PWM) and pulse density modulation(PDM) control scheme is discussed in this paper in order to extend the soft switching operation ranges and to improve the power conversion efficiency at the low power settings. The power converter practical effectiveness is substantially proved based on experimental results from practical design example.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.219.1-219.1
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• 2014

전자소자 산업의 미세화 및 대형화에 따라 플라즈마 밀도, 전위, 온도, 균일도 등 과 같은 플라즈마 특성을 제어하는 것은 차세대 플라즈마 장치 개발에 있어 매우 중요한 요소라고 할 수 있다. 특히, 급격한 소자의 미세화에 따라 플라즈마 공정을 통해 발생할 수 있는 damage는 큰 issue가 되어 왔고, 많은 연구자들은 이를 해결하기 위해서 다각적인 노력을 진행해 왔다. 그중 높은 전자 온도는 높은 전자 에너지에 의해 공정 중 소자를 손상 시키는 주된 원인이라고 보고되고 있으며, 이에 대한 제어기술은 매우 중요하다고 할 수 있다. 본 연구에서는 서로 다른 두 개의 내/외측으로 나뉘어진 나선형 모양의 ICP 안테나를 이용 하여 연구를 진행하였다. 내측의 안테나에는 2 MHz를 연결 하였으며, 외측의 안테나에는 13.56 MHz를 연결 하였으며, 내/외측 안테나에 각각 pulse mode로 입력전력을 인가해 줌으로써 플라즈마의 특성을 관찰하였다. Pulse / CW (Continuous Wave) mode에 있어서 전자온도의 측정을 위해 emissive probe 를 이용하여 plasma potential과 floating potential을 측정하였으며, 이를 통하여 전자온도를 계산하여 구할 수 있었다. Duty ratio 및 pulsing frequency의 변화에 따른 전자온도의 변화를 확인 할 수 있었으며, 그에 따른 플라즈마 균일도를 ion saturation current를 측정함으로써 관찰할 수 있었다. 실제 식각 공정에 있어서 Pulsing 조건에 따른 식각 특성을 관찰하기 위해, SiO2, ACL (Amorphous Carbon Layer)에 대해 식각을 진행하였으며, 식각 메커니즘 분석을 위해 이온에너지 분포의 변화를 PSM (Plasma Sampling Mass-spectroscopy)을 이용하여 측정하였다.

• 한국자동차공학회논문집
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• 제20권2호
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• pp.70-77
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• 2012

The selective catalytic reduction(SCR) system used to reduce NOx in diesel engines requires an NO/$NO_2$ ratio of about 1 in exhaust emissions to realize the fast SCR mode at temperatures lower than $300^{\circ}C$. This study investigated the characteristics of a plasma system as a pre-active apparatus for the fast SCR reaction mode of an SCR system. Plasma was generated by the pulse corona discharge(PCD) method with a four-channel wire-cylinder reactor. This study showed that plasma was easily generated in the exhaust gas by the PCD system, and the peak voltage of the normal state condition for plasma generation was generally 12 kV. The PCD system easily converted NO into $NO_2$ at lower temperatures and the NO/$NO_2$ conversion ratio increased with the discharge current for plasma generation. But the PCD system could not convert NO into $NO_2$ at higher engine speeds and higher engine loads due to the lack of oxygen in exhaust gas. The PCD system also activated the diesel oxidation catalysts(DOC) system to reduce CO emissions.

• 전기학회논문지P
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• 제57권2호
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• pp.72-78
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• 2008

The speed variation of SRM is fulfilled throughout a transition from chopping control to single pulse operation. (i,e., low speed to high speed operation). It is unsatisfied with performance at all operational regimes. In this paper, the operational performance of SRM can be improved by using current hysteresis control method. This method maintains a generally flat current waveform. At the high speed, the current chopping capability is lost due to the development of the back-EMF. Therefore SRM operates in single pulse mode. By using zero-current switching and zero-voltage switching technique, the stress of power switches can be reduce in chopping mode. When the commutation from one phase winding to another phase winding, the current can be zero as fast as possible in this period because several times negative voltage of DC-source voltage produce in phase winding. This paper is compared to performance based on conventional C-dump converter topology and the proposed resonant C-dump converter topology. Simulation and experimental results are presented to verify the effectiveness of the proposed circuit.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제48권8호
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• pp.448-454
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• 1999

This paper describes a new dc-ac inverter system which for achieving sinusoidal ac waveform makes use of parallel loaded high frequency resonant inverter consisting of full bridge. Each one of the pair of switches in the inverter is driven to synchronous output frequency and the other is driven to PWM signal with resonant frequency proportional to magnitude of sine wave. A forced discontinuous conduction mode is used to realize the quasi-sinusoidal pulse in each switching period. Therefore the inverter generates sinusoidal modulated output voltage including carrier frequency that is resonant frequency. Carrier frequency components of modulated output voltage is filtered by low pass filter. Since current through switches is always zero at its turn-on in the proposed inverter, low stress and low switching loss is achieved. Operating characteristics of the proposed system is analyzed in per unit system using computer simulation. The output voltage of if includes low harmonics and it is almost close to sine wave. Also, the theoretical analysis is proved through the experimental test.