• 대한전자공학회:학술대회논문집
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• 대한전자공학회 1998년도 추계종합학술대회 논문집
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• pp.779-782
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• 1998

This paper describes a high-speed Dual-modulus Prescaler (DMP) for RF mobile communication systems with pulse remover using selective latch technique. This circuit achieves high speed and low power consumption by reducing full speed flip-flops and using a selective latch. The proposed DMP consists of only one full speed flip-flop, a selective latch, conventional flip-flops, and a control gate. In order to ensure the timing of control signal, duty cycle problem and propagation delay must be considered. The failling edgetriggered flip-flops alleviate the duty cycle problem andthis paper shows that the propagation delay of control signal doesn't matter. The maximum operating frequency of the proposed DMP with 0.6um CMOS technology is up to 2.2㎓ at 3.3V power supply and the circuit consumes 5.24mA.

• Journal of Electrical Engineering and Technology
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• 제7권5호
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• pp.714-723
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• 2012

A new Z-source inverter (ZSI) topology is developed to improve voltage boost ability. The proposed topology is modified from the switched inductor topology by adding some more inductors and diodes into inductor branch to the conventional Z-source network. The modulation methods developed for the conventional ZSI can be easily utilized in the proposed ZSI. The proposed ZSI has an ability to obtain a higher voltage boost ratio compared with the conventional ZSI under the same shoot-through duty ratio. Since a smaller shoot-through duty ratio is required for high voltage boost, the proposed ZSI is able to reduce the voltage stress on Z-source capacitor and inverter-bridge. Theoretical analysis and operating principle of the proposed topology are explicitly described. In addition, the design guideline of the proposed Z-source network as well as the PWM control method to achieve the desired voltage boost factor is also analyzed in detail. The improved performances are validated by both simulation and experiment.

• Journal of Electrical Engineering and Technology
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• 제10권4호
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• pp.1566-1577
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• 2015

A novel high step-up converter is presented herein, which combines the conventional buck-boost converter, the charge pump capacitor and the coupling inductor. By doing so, a quite high voltage conversion ratio due to not only the turns ratio but also the duty cycle, so as to increase design feasibility. It is noted that the denominator of the voltage conversion ratio is the square of one minus duty cycle. Above all, there is no voltage spike across the switch due to the leakage inductance and hence no passive or active snubber is needed, and furthermore, the used switch is driven without isolation and hence the gate driving circuit is relatively simple, thereby upgrading the industrial application capability of this converter. In this paper, the basic operating principles and the associated mathematical deductions are firstly described in detail, and finally some experimental results are provided to demonstrate the effectiveness of the proposed high step-up converter.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2002년도 하계종합학술대회 논문집(5)
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• pp.257-260
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• 2002

In this paper, the circuit of AC Choppers for $CO_2$laser Power Supply are proposed and investigated. IGBT-controlled ac voltage regulators, operating at high frequency chopping mode. Chopping-to-supply duty ratio plays an important role in terms of laser output. Laser input energy is varied by controlling the leakage transfomer used with the proposed system. This improved circuit employs a 3 electrode-type and Ring Blower. This improved circuit system has many advantages compared with the conventional SMPS such as simple design requirment, easy implementation, high reliability, low switching loss, and consequently high efficiency. As a result, the maximun output was 16W at duty-ratio of 92%, total gas mixture of $CO_2$: $N_2$: He = 1 : 9 : 15, total pressure of 15torr.

• 한국조명전기설비학회:학술대회논문집
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• 한국조명전기설비학회 2000년도 학술대회논문집
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• pp.188-192
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• 2000

This paper presents a novel prototype of soft-switching PWM Full-bridge converter which incorporates active power switches in series with each rectifier diode in transformer secondary side. Switching and conduction losses of all the switches and devices are reduced as well as commutating current and circulating current flowing through transformer as compared with conventional converter. And duty ratio of primary switches is constant for maximum voltage conversion ratio. But this converter can be varied output by duty ratio of secondary switches. Operation principles basically the same as that of the PWM Full-bridge converter published previously. The operating characteristics of this converter are illustrate and discussed including the simulated analysis.

• 한국유체기계학회 논문집
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• 제17권4호
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• pp.70-75
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• 2014

In this paper a analysis method is presented to obtain the steady state dynamic response from the finite element based equations of a rotor-bearing system with initial deflection. The method has been applied to analyze the dynamic response of the two-shaft rotor-bearing system with rigid coupling offset in a heavy duty gas turbine-generator. Bumps in the dynamic response of each rotor system have been observed at each critical speed due to the effect of initial deflection for rigid coupling offset. And, the dynamic responses have been shown to reduce for operating condition changes from cold to hot.

• 조명전기설비학회논문지
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• 제30권3호
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• pp.65-72
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• 2016

This paper discussed the LCL-type & Isolated bidirectional dc-dc converter(BDC) with dual full bridge inverter. In order to verify the analysis of the BDC, Experimental prototype has been designed and implemented to supply constant voltage regardless of loads and proposed a method to select switching frequency that depended on two inductors' inductance ratio and transformer parameters. The proposed converter has been composed of LCL resonant network with unit inductance ratio ($L_r/L_f$=1) and then operated with fixed duty, 50% duty ratio and fixed frequency. There are some characteristics that input voltage and output voltage of the BDC is nearly identical and zero voltage turn-on switching is possible in forward and reverse mode. Finally, it has been showed that BDC is possible to commutate operating mode normally and provide constant output voltage in selected switching frequency.

• 전력전자학회논문지
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• 제19권3호
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• pp.220-226
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• 2014

Input current ripple and harmonic components of the power device are main causes of electromagnetic interference (EMI). Although the discontinuous conduction mode (DCM) operation can reduce harmonic components of the power device by reducing reverse recovery current of diode and turn-off voltage spikes of the switch, input current ripple increases due to high peak to peak inductor current. Therefore, in this paper, frequency control algorithm is proposed to reduce the input current ripple of DCM operated interleaved boost converter. In the proposed algorithm, duty ratio is fixed either 0.33 or 0.67 to minimize the input current ripple and the switching frequency is controlled according to operating conditions. 600 W 3-phase interleaved boost converter prototype system is built to verify proposed algorithm.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2012년도 전력전자학술대회 논문집
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• pp.23-24
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• 2012

본 논문에서는 전기자동차용 탑재형 충전기회로 (On-Board Charger, OBC) 에 사용되는 부하 직렬 공진형 컨버터 (Series loaded Resonant DC-DC Converter, SRC) 의 정전압 제어를 위해 기존에 듀티를 고정하고 주파수만을 제어하던 방법에 듀티도 같이 제어하는 비대칭 듀티 제어 방법 (Asymmetrical Duty Cycle Control) 을 적용하였다. 적용한 SRC-OBC의 등가화 모델의 수식적 분석을 통해 제안한 회로의 동작영역을 도출하여 결과로 얻어진 동작영역에서 제안한 회로의 부하에 따른 효율을 기존 주파수 제어 방법과 비교 분석을 통하여 적용한 제어 방법의 타당성을 검증한다.

• 농촌의학ㆍ지역보건
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• 제29권1호
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• pp.91-100
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• 2004

시대의 변천에 따라 보건진료원의 업무활동 내용의 변화를 전라북도내에 근무하는 보건진료원을 대상으로 비교 분석한 결과는 다음과 같다. 1) 보건진료원의 수는 1989년 255명에서 2000년 224명으로 감소하였다. 2) 보건진료원의 일반적 특성은 1989년에 비하여 2000년에 연령, 기혼자, 근무경력이 증가하였다. 3) 보건진료원의 시간별 업무량은 1989년과 2000년 모두 진료업무가 가장 높았고, 1989년에 비해 2000년에는 모성보건, 영 유아보건, 가족계획, 진료업무, 결핵관리가 현저히 감소하였으며, 2000년에는 업무시간에 지역사회보건정보수집이 새롭게 추가된 것으로 조사되었다. 4) 1일 평균 진료환자 수 및 주민과의 친밀도는 1989년보다 2000년에 증가하였다. 근무에 대한 만족도는 1989년에 보통이다, 괜찮은 직업이라 생각한다, 보람을 느끼고 있다 라고 응답한 경우가 36.6%, 37.4%, 17.6% 이었던 반면에 2000년에는 11.6%, 22.6%, 56.8%로 보람을 느끼고 있다 고 응답한 경우가 증가하였다. 5) 지역사회의 실정을 감안할 때 가장 필요한 업무라고 응답 한 경우 진료업무가 57.7%이었으며, 보건교육이 31.4%, 지역사회보건정보수집이 10.9%순으로 나타났다. 또한 불필요한 업무로는 가족계획이 68.8%로 가장 높았고, 결핵관리 11.1 %, 영 유아보건 6.3%, 모성보건 5.6%순으로 조사되었다. 6) 보건진료소 이용도 감소 시 가장 바람직한 방안으로는 새로운 보건기능을 수행하는 기관으로 전환이 79.0% 이었으며, 기타(가정방문, 만성질환 및 노인환자 건강관리)가 12.3%로 조사되었다. 이상의 결과로 보아 보건진료원은 본인의 직능에 대하여 지역사회주민의 접근성 및 친밀도가 높고 직업에 대한 만족도가 높은 것으로 인식하고 있으며, 업무는 시대의 변화에 따라 감소하는 추세이고, 지역주민의 보건진료소 이용 감소 시 보건진료원은 새로운 보건기능을 수행하는 기관으로 전환을 원하고 있는 것으로 조사되었다. 그러므로 보건진료소의 현 실태를 정확히 인식하고, 보건진료원의 장점, 즉 지역사회에 대한 높은 접근성과 친밀도 및 전문성을 도대로 공공보건사업 기능이 강화된 새로운 역할을 모색함이 바람직하다고 판단된다.