• Journal of IKEEE
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• v.23 no.3
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• pp.1104-1107
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• 2019

This paper proposes a DC-DC boost converter for wearable AMOLED display using dead time controller to reduce dead time and improve power efficiency. Also the DC-DC boost converter adopts PWM-SPWM (set-time variable pulse width modulation) dual-mode to enhance power efficiency under light load and decrease output voltage ripple. The proposed circuit has been designed using $0.18{\mu}m$ BCDMOS process. Simulation results show that the circuit has power efficiency of 39%~96% and output ripple voltage of 2 mV under load current range of 1 mA~70 mA. The power efficiency of the proposed circuit is up to 2% higher than the previous PWM-SPWM method and up to 8% higher than only PWM method.

• Journal of IKEEE
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• v.23 no.1
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• pp.254-260
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• 2019

The failure rate of bidirectional dc-to-dc converter is predicted through the failure mode and effect analysis (FMEA) and the fault-tree analysis (FTA) considering the operational risk. In order to increase the driving voltage of the electric vehicle efficiently, the bidirectional converter is attached to the front of the inverter. It has a boost mode for discharging battery power to the dc-link capacitor and a buck mode for charging the regenerative power to the battery. Based on the results of the FMEA considering the operating characteristics of the bidirectional converter, the fault-tree is designed considering the risk of the converter. After setting the design parameters for the MCU for the electric vehicle, we analyze the failure rate of the capacitor due to the output voltage ripple and the inductor component failure rate due to the inductor current ripple. In addition, we obtain the failure rate of major parts according to operating temperature using MIL-HDBK-217F. Finally, the failure rate and the mean time between failures (MTBF) of the converter are predicted by reflecting the part failure rate to the basic event of the fault-tree.

• Journal of the Korean Solar Energy Society
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• v.32 no.spc3
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• pp.289-294
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• 2012

In recent years, understanding the dynamics of DC distribution system has become critically important due mainly to the increasing needs for the interconnection of DC distributed generators and the (DC-based) electric vehicle (EV) charging systems. In this paper, the characteristics of the DC grid system connected to the compact proton exchange membrane fuel cell (PEMFC) has been studied. In particular, the voltage and current transient phenomena were measured by varying the load of the DC grid system. Also, the voltage and current ripple were measured at the different load conditions. Our experimental results clearly manifested that the study contributes to the establishment of fundamental method to characterize the small DC grid system including distributed generation.

• Journal of IKEEE
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• v.18 no.3
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• pp.320-327
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• 2014

Recently, Importance of power management circuit technology is increased with the development of portable electric devices. This paper presents a high performance DC-DC buck converter for mobile applications. Especially, presented design have low ripple voltages and driving capability of large load current. A designed voltage mode 2-phase DC-DC converter is implemented in a $0.35{\mu}m$ CMOS process, and the overall size is $2.35{\times}2.35mm^2$. The peak efficiency is 91% with a 4MHz frequency and the maximum load current is 4A.

• 한국태양에너지학회:학술대회논문집
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• 2012.03a
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• pp.414-418
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• 2012

In recent years, understanding the dynamics of DC distribution system has become critically important due mainly to the increasing needs for the interconnection of DC distributed generators and the (DC-based) electric vehicle (EV) charging systems. In this paper, the characteristics of the DC grid system connected to the compact proton exchange membrane fuel cell (PEMFC) has been studied. In particular, the voltage and current transient phenomena were measured by varying the load of the DC grid system. Also, the voltage and current ripple were measured at the different load conditions. Our experimental results clearly manifested that the study contributes to the establishment of fundamental method to characterize the small DC grid system including distributed generation.

• Journal of IKEEE
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• v.4 no.2 s.7
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• pp.225-232
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• 2000

Dead time which is inserted in PWM signals of VSI distorts the inverter output voltage waveforms and deteriorate the control performance of an induction machine by producing torque ripples. In this paper, dead time compensation method in a vector controlled induction machine is proposed. The method is based on a feedforward approach that compensates dead time effect by adding the compensating voltages to the inverter output voltage references in 2 phase stationary frame. The proposed method is only software intensive and easy to realize without additional hardware. The experimental results show the validity and effectiveness of the proposed method.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.20 no.7
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• pp.74-80
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• 2006

This paper describes a solar energy conversion strategy is applied to grid-connected single phase inverter by the maximum power point of conversion strategy. The maximum power point of tracking is controlled output power of PV(photovoltaic)modules, based on generated circuit control MOSFET switch of two boost converter for a connected single phase inverter with four IGBT's switch in full bridge. The generation control circuit allows each photovoltaic module to operate independently at peak capacity, simply by detecting of the output power of PV module. Furthermore, the generation control circuit attenuates low-frequency ripple voltage. which is caused by the full-bridge inverter, across the photovoltaic modules. The effectiveness of the proposed inverter system is confirmed experimentally and by means of simulation.

• The Transactions of the Korean Institute of Power Electronics
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• v.10 no.4
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• pp.388-396
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• 2005

SRM has not been put into practical applications widely because of its large torque ripple, acoustic noise and low power factor. In addition, a traditional position sensor is needed for the drive control. So we propose an improved sensorless drive method of Switched Reluctance Motors using impressed voltage pulses. Conventional impressed voltage pulse method has a problem of phase delay because of low-pass filter. So in this paper we propose an unproved sensorless driving method based on the impressed voltage pulse using new pulse-shift circuit technique that overcomes the phase delay and start-up problem. Proposed method is implemented in a simple analog circuit instead of using an expensive DSP.

• Proceedings of the KIEE Conference
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• 2005.07b
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• pp.1377-1379
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• 2005

독립형 태양광 발전시스템은 태양전지, 배터리, 충 방전 제어기, 컨버터, 부하로 나눌 수 있다. 태양광 발전은 비선형 전압전류 특성을 가지고 있기 때문에 발전효율을 최대한 높이기 위해 최대전력추종제어(MPPT)를 하게된다. 또한 부하가 여러 개일 경우에는 다양한 출력이 요구되는데, 이를 위해 강압 및 승압이 가능한 컨버터가 필요하게 된다. 그러나 다중부하에는 다수의 컨버터와 각각의 컨버터를 제어하기 위한 제어기가 필요하게 되므로 cost가 증가요인이 된다. 따라서 본 논문에서는 승 강압에 의한 다중출력을 갖는 병렬구조의 DC-DC컨버터를 제안하고자 한다. 제안된 컨버터는 입력전압을 승 강압하여 두 개의 출력전압을 갖는다. 강압동작은 일반적인 buck형 컨버터에 커패시터를 추가하여 구성하였고, 승압을 위해서는 리플율이 적은 Coupling inductor를 이용하고 커패시터를 추가하여 두 개의 컨버터를 병렬로 구성하였다. 컨버터의 병렬제어를 위해 제어기를 설계하고 이를 시뮬레이션 하였다.

• 한국신재생에너지학회:학술대회논문집
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• 2010.11a
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• pp.73.2-73.2
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• 2010

휴대용 전자기기들의 소비전력 증가에 따라 2차전지에 비해 에너지 밀도가 높은 연료전지를 이용한 충전기의 필요성이 부각되고 있다. 대다수의 충전기는 On-Grid 방식으로 벅타입 컨버터를 이용한 감압 방식이었으나, 연료전지를 이용할 경우 승압식 컨버터를 통한 배터리의 충전이 요구된다. 또한 배터리는 일반 저항부하와 달리 큰 커패시턴스 성분을 가지고 있기 때문에 컨버터의 출력단에 인덕터가 없는 경우 큰 출력 리플전류를 유도하게 되어 시스템의 효율과 배터리의 수명에 좋지 않은 영향을 끼치게 된다. 또한 이를 해결하기 위해 절연형 감압 컨버터를 사용하는 경우 변압기 사용에 의한 부피 증가와 부가 소자의 사용에 따른 가격 상승을 피하기 어렵다. Cuk 컨버터는 주스위치의 ON/OFF 동작에 관계없이 출력으로 에너지가 항상 전달되며, 이상적으로 리플이 거의 존재하지 않아 충전용으로 적합하다. 또한, 승압 및 감압이 자유롭기 때문에 배터리의 정격전압에 상관없는 범용 충전기의 설계도 가능하다. 따라서 본 논문에서는 Cuk 컨버터를 이용하여 배터리 충전기를 설계하고, 그의 상태공간 모델링, 주파수 특성 해석 및 제어기 설계에 대해 기술한다. 제안된 제어 방식은 소형 연료전지 스택을 이용하여 실제 배터리를 대상으로 한 정전류 및 정전압 제어를 실행하여 그 성능 및 안정성을 검증한다.