Dynamic Element Matching을 통한 Multi-bit Delta-Sigma Modulator에서의 DAC Error 감소 방안 비교

현덕환,Hyun, Deok-Hwan 한국정보통신학회 2006 한국정보통신학회논문지 Vol.10 No.1

고정도, 저주파용 데이터 변환기로 사용되어온 델타-시그마 변환기는 그 출력 단에 1 bit 혹은 multi-bit 양자화기(ADC)를 사용할 수 있다. 이 중 multi-bit 양자화기를 사용하는 경우 궤환회로에도 multi-bit DAC을 사용하여야 하며 시스템의 데이터 변환 정확도는 DAC의 비선형성에 직접적인 영향을 받는다. 이 영향을 최소화하여 델타-시그마 변환기의 변환 정확도를 높이기 위해서는 DAC에 사용되는 단위 데이터 변환소자 간의 오차가 시스템에 미치는 영향을 최소화 하여야한다. 이 과정 즉 Dynamic Element Matching을 위하여 제안된 4가지 방안(DER, CLA, ILA, DWA)을 비교 설명하였다. 그리고 각 방안을 사용하였을 때 시스템 출력의 잡음 특성을 비교 하였다. 이중 DWA(Data Weighted Averaging) 방안이 가장 우수한 출력 특성을 보였다. The advantage of the DSM which employ multi-bit quantizer is the increased SNR at the modulator's output. Typically 6 dB improvement is effected for every one additional bit. But multi-bit quantizer evidently requires multi-bit DAC in the feedback loop. The integral linearity error of the feedback DAC has direct impact upon the system performance and degraded SNR of the system. In order to mitigate the negative impact the DAC has on the system performance, many DEM(Dynamic Element Matching) schemes has been proposed. Among the proposed schemes, four schemes(DER,CLA,ILA,DWA) are explained and its performance has been compared. DWA(Data Weighted Averaging) method shows the best performance of the all.

공정가스와 RF 주파수에 따른 웨이퍼 표면 텍스쳐 처리 공정에서 저반사율에 관한 연구

윤명수,현덕환,진법종,최종용,김정식,강형동,이준신,권기청,Yun, Myoung-Soo,Hyun, Deoc-Hwan,Jin, Beop-Jong,Choi, Jong-Young,Kim, Joung-Sik,Kang, Hyoung-Dong,Yi, Jun-Sin,Kwon, Gi-Chung 한국진공학회 2010 Applied Science and Convergence Technology Vol.19 No.2

Conventional surface texturing in crystalline silicon solar cell have been use wet texturing by Alkali or Acid solution. But conventional wet texturing has the serious issue of wafer breakage by large consumption of wafer in wet solution and can not obtain the reflectance below 10% in multi crystalline silicon. Therefore it is focusing on RIE texturing, one method of dry etching. We developed large scale plasma RIE (Reactive Ion Etching) equipment which can accommodate 144 wafers (125 mm) in tray in order to provide surface texturing on the silicon wafer surface. Reflectance was controllable from 3% to 20% in crystalline silicon depending on the texture shape and height. We have achieved excellent reflectance below 4% on the weighted average (300~1,100 nm) in multi crystalline silicon using plasma texturing with gas mixture ratio such as $SF_6$, $Cl_2$, and $O_2$. The texture shape and height on the silicon wafer surface have an effect on gas chemistry, etching time, RF frequency, and so on. Excellent conversion efficiency of 16.1% is obtained in multi crystalline silicon by RIE process. In order to know the influence of RF frequency with 2 MHz and 13.56 MHz, texturing shape and conversion efficiency are compared and discussed mutually using RIE technology. 일반적으로 결정질 실리콘 태양전지에서 표면에 텍스쳐링(texturing)하는 것은 알칼리 또는 산성 같은 화학용액을 사용하고 있다. 그러나 실리콘 부족으로 실리콘의 양의 감소로 인하여 웨이퍼 두께가 감소하고 있는 추세에 일반적으로 사용하고 있는 습식 텍스쳐링 방법에서 화학용액에 의한 많은 양의 실리콘이 소모되고 있어 웨이퍼의 파손이 심각한 문제에 직면하고 있다. 그리하여 습식 텍스쳐링 방법보다는 플라즈마로 텍스쳐링할 수 있는 건식 텍스쳐링 방법인 RIE (reactive ion etching) 기법이 대두되고 있다. 그리고 습식 텍스쳐링으로는 결정질 실리콘 태양전지의 반사율을 10% 이하로는 낮출 수가 없다. 다결정 실리콘 웨이퍼 표면에 텍스쳐링을 하기 위하여 125 mm 웨이퍼 144개를 수용할 수 있는 대규모 플라즈마 RIE 장비를 개발하였다. 반사율을 4% 이하로 낮추기 위하여 공정가스는 $Cl_2$, $SF_6$, $O_2$를 기반으로 RIE 텍스쳐링을 하였고 텍스쳐링의 모양은 공정가스, 공정시간, RF 주파수 등에 의해 조절이 가능하였다. 본 연구에서 RIE 공정을 통하여 16.1%의 변환효율을 얻었으며, RF 주파수가 텍스쳐링의 모양에 미치는 영향을 살펴보았다.

RIE 표면 텍스쳐링 모양에 따른 결정질 실리콘 태양전지의 영향

박인규,윤명수,현덕환,진법종,최종용,김정식,강형동,권기청,Park, In-Gyu,Yun, Myoung-Soo,Hyun, Deoc-Hwan,Jin, Beop-Jong,Choi, Jong-Yong,Kim, Joung-Sik,Kang, Hyoung-Dong,Kwon, Gi-Chung 한국진공학회 2010 Applied Science and Convergence Technology Vol.19 No.4

다결정 실리콘 웨이퍼 표면에 대면적 reactive ion etching (RIE) 장비로 표면 텍스쳐를 형성한 뒤 태양전지를 제작하였다. 웨이퍼 표면에 텍스쳐를 형성하는 것은 광학적 손실을 줄이기 위해 일반적으로 사용되는 방법으로 alkaline etching이 사용된다. 그러나 다결정 실리콘 태양전지의 경우 재료의 결정 방향에 따라 식각되는 alkaline etching은 텍스쳐링의 모양을 제어할 수 없어 효과적이지 못하다. 이와 달리 플라즈마 식각방법을 사용하면 표면 텍스쳐의 모양을 효과적으로 제어하여 조금 더 낮은 반사율을 얻을 수 있다. 하지만 텍스쳐 모양 조절로 얻은 낮은 반사율이 항상 높은 변환효율을 얻을 수 있는 것은 아니다. 본 연구에서는 대면적 RIE 공정 조건별로 얻은 태양전지 표면 텍스쳐의 모양에 따라 각각의 반사율과 양자효율 및 변환효율이 미치는 영향을 살펴보았다. We fabricated a plasma texturing for multi-crystalline silicon cells using reactive ion etching (RIE). Multi-crystalline Si cells have not benefited from the cost-effective wet-chemical texturing processes that reduce front surface reflectance on single-crystal wafers. Elimination of plasma damage has been achieved while keeping front reflectance to extremely low levels. We will discuss reflectance, quantum efficiency and conversion efficiency for multi-crystalline Si solar cell by each RIE process conditions.

에미터 랩쓰루 실리콘 태양전지 개발

조재억(Jaeeock Cho),양병기(Byungki Yang),이홍구(Honggu Lee),현덕환(Deochwan Hyun),정우원(Woowon Jung),이대종(Daejong Lee),홍근기(Keunkee Hong),이성은(Seong-Eun Lee),홍정의(Jeongeui Hong) 한국태양광발전학회 2013 Current Photovoltaic Research Vol.1 No.1

In contrast to conventional crystalline cells, back-contact solar cells feature high efficiencies, simpler module assembly, and better aesthetics. The highest commercialized cell and module efficiency was recorded by n-type back-contact solar cells. However, the mainstream PV industry uses a p?type substrate instead of n-type due to the high costs and complexity of the manufacturing processes in the case of the latter. P-type back-contact solar cells such as metal wrap?through and emitter wrap-through, which are inexpensive and compatible with the current PV industry, have consequently been developed. In this paper the characteristics of EWT (emitter wrapthrough) solar cells and their status and prospects for development are discussed.

EWT 태양전지 제작을 위한 레이저 미세 관통홀 가공 기술

이홍구(Lee,Hong-Gu),서세영(Seo,Se-Young),현덕환(Hyun,Deoc-hwan),이용화(Lee,Yong-wha),김강일(Kim,Gang-il),정우원(Jung,Woo-won),이아름(Lee,Ah-Reum),조재억(Cho,Jaee-ock) 한국태양에너지학회 2011 한국태양에너지학회 논문집 Vol.31 No.4

Laser drilling or vias is the one of key technologies in developing Emitter-Wrap Through(EWT) solar cell which is particularly attractive due to the use of industrial processing and common solar grade p-type silicon materials. While alternative economically feasible drilling process is not available to date, the processing time and laser induced damage should be as small as possible in this process. This paper provides an overview on various factors that should be considered in using the laser via drilling technology for developing highly efficient and industrially applicable EWT solar cells.

Wrap Through 태양전지의 효율 향상을 위한 Hole 가공과 열처리 기술

홍근기(Hong, Keun-Kee),이대종(Lee, Dae-Jong),정우원(Jung, Woo-Won),이홍구(Lee, Hong-Gu),현덕환(Hyun, Deoc-Hwan),양병기(Yang, Byung-Ki),이성은(Lee, Seong-Eun),조재억(Cho, Jae-Eock),홍정의(Hong, Jeong-Eui) 한국태양에너지학회 2013 한국태양에너지학회 학술대회논문집 Vol.2013 No.4

In contrast to the conventional crystalline, back-contact solar cells feature high efficiencies, simpler module assembly, and better aesthetics. The highest commercialized cell and module efficiency is recorded by n-type back-contact solar cells. However, the mainstream PV industry uses p-type substrate instead of n-type due to high costs and complexity of manufacturing processes. Therefore p-type back-contact solar cells such as metal wrap-through and emitter wrap-through which are low cost and compatible with current PV industry have been developed. In this paper, we studied for hole formation process and firing process of EWT solar cells, status and prospects for development of EWT solar cell will be discussed.

Multibit Delta-Sigma Modulator 에서의 Dynamic Element Matching 방안 비교

현덕환 경주대학교 2004 論文集 Vol.17 No.-

The advantage of the DSM which employ multi-bit quantizer is the increased SNR at the modulator's output. Typically 6 dB improvement is expected for every one additional bit. But multi-bit quantizer evidently requires multi-bit DAC in the feedback loop. The integral linearity error of the feedback DAC has direct impact upon the system performance and degrade SNR of the system. In order to mitigate the negative impact the DAC has on the system performance, many DEM(Dynamic Element Matching) schemes has been proposed. Among the proposed schemes, four schemes(DER,CLA,ILA,DWA) are explained and its performance has been compared. DWA(Data Weighted Averaging) method shows the best performance of the all.

초소형 전기자동차 소요 에너지 개념 설계

현덕환 경주대학교 정보전자기술연구소 2008 情報電子技術論叢 Vol.7 No.-

The recent soaring price of crude oil has caused increased interest in the energy saving electric vehicles. This paper presents the basic design considerations for the electric vehicle(EV) in terms of energy requirement. Required amount of energy for the ultra light electric vehicle(EV) running on the pre-defined pattern has been calculated. Targeted vehicle weights less than 200kg including a driver. Max. running speed of 54km/h and cruising speed of 40km/h have been assumed. Various batteries- the primary power pack for the EV - has been compared and their relevant characteristics has been reviewed. Ultra capacitors also has been investigated for the purpose of using them as an auxiliary power source. As for the driving system of an EV, three types of motor has been compared. The total running cost of the outlined vehicle has been estimated to present the economy of the EV.

델타-시그마 변환기의 효과적인 dither 방안

현덕환 경주대학교 정보전자기술연구소 2003 情報電子技術論叢 Vol.2 No.-

Delta-Sigma Modulator(DSM) is an important building block for low-frequency high-resolution A/D and D/A converters. It continue to wide its application areas such as high fidelity audio, speech processing, frequency control systems, and digital audio circuits. One of the key advantages of the DSMs is that they do not require precise analog components which needs to be trimmed during calibration process. This makes the implementation of the DSM possible with low-cost CMOS circuitry in a form of switched-capacitor or switched-current circuits. But it suffers performance degradation due to so called pattern noise which came from the repetitive nature of the output sequences. In order to reduce the detrimental effects of the pattern noise, pseudo random noise signal is applied to the system as dither signal Pattern noise or idle channel tones have characteristics which is very difficult to observe or characterize due to its temporal nature. While reducing pattern noise, dither signal also degrade S/N ratio of the system. This paper addresses the negative impacts of the dither signal on the system performances. We propose an effective dithering scheme which does not degrade system performance. We also compare the results of the proposed method with conventional ones. Probability of the occurrence of the limit cycles and resulting SQNR(signal-to-quantization noise ratio) in the passband will be addressed.

텔타-시그마 변환기 구조에 따른 Pattern 잡음 비교

현덕환 경주대학교 2003 論文集 Vol.16 No.-

It is a well known phenomenon that Delta-Sigma Modulators(DSM) suffer pattern noise problem. These noise appear as the modulator output falls into a cyclic mode of operation. This paper addresses the dependence of these tone signals depending upon the system topologies. In a single stage DSMs there are four types of DSM topologies namely Cascade of Integrators with Feedback Form(CIFB), Cascade of Integrators with Feedforward Form(CIFF), Cascade of Resonators with Feedback Form(CRFB), and Cascade of Resonators with Feedforward Form(CRFF). We excluded the multi-stage DSMs, due to the difficulty caused by multi-bit output. The limit cycles depend upon the modulator input and initial conditions of the system. Armed with limit cycle detecting program, 4-types of the single-stage DSM are investigated. Due to its relatively high probability of pattern noise generation, system order was determined to be 3. Second order system usually generates too much pattern noise while 5-th or higher order systems do too seldom. The limit cycle detecting program first detect repetitive output sequences from the DSM output. After that the detected repetitive sequences are checked to determine whether that sequence could really repeat itself indefinitely as a DSM output. With changing initial conditions, each 4-types of single-stage DSMs were run 1000 times. Out of the 1000 runs, each DSM topology shows different numbers of limit cycles occurrence. Simulation results shows that the resonator type of the systems are more susceptible to the pattern noise than the integrator types of the system.