• Proceedings of the KIPE Conference
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• 2002.11a
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• pp.125-128
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• 2002

In this paper, a novel on-line do capacitance estimation method for the PWM converter is proposed. At no load, Input current at a low frequency is injected, which causes do voltage ripple. With the ac voltage and current ripple components of the dc side, the capacitance can be calculated. Experimental result shows that the estimation error is less than $2\%$.

• Proceedings of the KSR Conference
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• 2008.11b
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• pp.179-184
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• 2008

This paper presents the design of the feed forward controller to improve on the non-interference control performance of a single PWM converter in parallel for high-speed trains. The feed forward controller is designed to minimize the interference generated by converter switching in parallel operation of PWM converters. The gain value of the feed forward controller is calculated by inductance values of the input transformer. However, it is difficult to decide this gain value exactly because inductance values are changed by the operation condition of an input transformer. In this paper, the proposed design of feed forward controller can exactly decide the gain value using the leakage inductances estimated by detecting the variation of input current. the validity of the proposed feed forward controller is proved through the simulation results.

• Proceedings of the KIPE Conference
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• 2001.10a
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• pp.146-150
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• 2001

A new three-phase soft-switching active front-end inverter is presented. The topology consists of a quasi-resonant PWM boost converter with an additional resonant branch, which provides low loss at high frequency operation. This leads to a high conversion efficiency and a remarkable reduction in the size of the input inductor. To synchronise the PWM pattern with the resonance cycle, a modified space vector modulation with asymmetrical PWM pattern is used. A high power factor can be achieved for both power flow directions. Due to a new control strategy the converter features a low content of harmonics in the line currents even for distorted line voltages.

• Proceedings of the KIPE Conference
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• 2020.08a
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• pp.282-283
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• 2020

3상 컨버터에서 스위치의 개방고장이 발생한 경우 고장 전류에 직류 및 고조파 성분이 발생할 수 있으며, 보호회로에 의한 고장 감지가 어려우므로 주변 기기에 2차 고장이 발생할 수 있다. 단일 및 이중 스위치 개방고장의 경우 21가지 고장 모드가 존재한다. 본 논문에서는 이러한 고장 모드를 진단하기 위해 정지 좌표계 d-q축 전류의 직류 및 고조파 성분을 활용하는 two-step 구조의 ANN(Artificial Neural Network)을 제안한다. 고장 시에 발생된 직류 및 고조파 성분 전류는 ADALINE(Adaptive-Linear Neuron)을 통해 얻는다. 고장 진단의 첫 번째 단계에서는 직류 성분을 기반으로 ANN을 이용하여 고장모드를 6개 영역으로 분류한다. 두 번째 단계에서는 6개의 각 영역에서 직류 성분과 전류의 THD(Total Harmonics Distortion)를 기반으로 ANN을 이용하여 개방고장이 발생한 스위치를 진단한다. 제안된 Two-step 방법으로 고장을 진단하므로써 간단한 구조로 ANN의 설계가 가능하다. 3.7kW급 3상 PWM 컨버터로 실험을 통해 제안된 방법의 효용성을 검증하였다.

• Journal of Power Electronics
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• v.10 no.6
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• pp.673-679
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• 2010

Input-series-output-parallel (ISOP) connected DC-DC converters enable low voltage rating switches to be used in high voltage input applications. In this paper, a DSP is adopted to generate digital phase-shifted PWM signals and to fulfill the closed-loop control function for ISOP connected two full-bridge DC-DC converters. Moreover, a stable output current sharing control strategy is proposed for the system, with which equal sharing of the input voltage and the load current can be achieved without any input voltage control loops. Based on small signal analysis with the state space average method, a loop gain design with the proposed scheme is made. Compared with the conventional IVS scheme, the proposed strategy leads to simplification of the output voltage regulator design and better static and dynamic responses. The effectiveness of the proposed control strategy is verified by the simulation and experimental results of an ISOP system made up of two full-bridge DC-DC converters.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.49 no.8
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• pp.35-40
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• 2012

In DC-DC converters, a PWM/PFM dual mode control method is commonly used to maintain a high efficiency over a wide range of load variation. Since the control mode is selected according to the load condition, the chip area is increased due to additional circuit for mode control and the optimum efficiency cannot be achieved around the mode transition point. To solve such problems, a new integrated control method is proposed in this paper, in which a PLL is used in the current mode PWM control circuit instead of an oscillator. The proposed integrated control method is verified through a design of a buck converter using PSIM simulation. Simulation of the complete buck converter circuit by Cadence Spectre showed a maximum efficiency of 94.7% at a load current of 250mA and an efficiency of 85.4% at a load current of 10mA under the light load condition.

• The Transactions of the Korean Institute of Power Electronics
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• v.7 no.4
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• pp.346-352
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• 2002

A novel Zero Current Switching(ZCS) Pulse Width Modulation(PWM) boost converter with dual mode for reducing two rectifiers reverse recovery related losses is proposed. The switches of the proposed converter are operating to work alternatively turn-on and turn-off with soft switching condition In the every cycle and the proposed converter reduces the reverse recovery current, which is related switching losses and EMI problems, of the free-wheeling diode$(D_1, D_2)$ by adding the resonant inductor Lr, in series with the switch $S_1$. The switching components$(S_1, S_2, D, D_1)$ in the proposed boost converter are subjected to minimum voltage and current stresses same as those in their PWM counterparts because there are no additional active switches and resonant elements compared with the conventional ZVT PWM $converters^{[2]}$. The operation of the proposed converter, in this paper, is analyzed and to verify the feasibility of the characteristics is built and tested.

• Journal of the Institute of Electronics and Information Engineers
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• v.49 no.11
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• pp.193-198
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• 2012

An LED converter used to operate an LED with high efficiency and long lifespan, activates an LED by keeping voltage and current constant. In spite of voltage drop by LED's overheating and over-voltage by damage of a power line and by circuit problem, most existing LED converters supply unchanged constant voltage and current to the LED. Eventually, LED is out of order because of over-voltage or over-current. To avoid the breakdown of an LED by over-voltage and over-current, we propose a new scheme which deactivate the PWM circuit in the event of over-current generating. The PWM circuit operates below the pre-determined level of current. While the over-voltage is generated in PWM circuit, the feedback circuit makes the PWM circuit stopped and therefore prevents LED from being damaged by over-voltage and over-current.

• Proceedings of the KIEE Conference
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• 1996.07a
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• pp.521-524
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• 1996

A new zero voltage and nero current switching(ZVZCS) full bridge(FB) PWM converter b proposed to improve the performance of the previously presented ZVZCS-FB-PWM converters [7,8]. By adding a secondary active clamp and controlling the clamp switch moderately, ZVS(for leading-leg switches) are ZCS(for lagging-leg switches) are achieved without nay lossy components, the reverie avalanche break down of leading-leg IGBTs[7] or the saturable reactor in the primary[8]. Many advantages including simple circuit topology, high efficiency, and low cost mate the new converter attractive for high voltage and high power(> 10 kW) applications. The principle of operation is explained and analyzed. The features and design considerations of the new converter are also illustrated and verified on an 1.8 kW, 100 kHz IGBT based experimental circuit.

• The Transactions of the Korean Institute of Power Electronics
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• v.6 no.6
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• pp.556-563
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• 2001

In this paper a new zero current transition pulse width modulation (ZCT-PWM) buck converter is proposed to combine the desirable feature of both the conventional buck converter and resonant converters. In this proposed scheme an auxiliary circuit is added to the conventional buck converter and used to achieve soft-switching for both the main switch and the freewheeling diode while not incurring any additional losses due to auxiliary circuit And this converter operates exactly like the conventional PWM converter except for a short particular time interval. The operation of the proposed converter is explained and analyzed. and design guidelines are presented. To validate the feasibility of the proposed converter, a 100KHz 180-W prototype is built and tested.