• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2005.11a
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• pp.415-420
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• 2005

This paper presents the two lossless auxiliary inductors-assisted voltage source type half bridge (single ended push pull: SEPP) series resonant high frequency inverter for induction heated king roller in copy and printing machines. The simple high-frequency inverter treated here can completely achieve stable zero current soft switching (ZCS) commutation for wide its output power regulation ranges and load variations under its constant high frequency pulse density modulation (PDM) scheme. Its transient and steady state operating principle is originally described and discussed for a constant high-frequency PDM control strategy under a stable ZCS operation commutation, together with its output effective power regulation characteristics-based on the high frequency PDM strategy. The experimental operating performances of this voltage source SEPP ZCS-PDM series resonant high frequency inverter using IGBTs are illustrated as compared with computer simulation results and experimental ones. Its power losses analysis and actual efficiency are evaluated and discussed on the basis of simulation and experimental results. The feasible effectiveness of this high frequency inverter appliance implemented here is proved from the practical point of view.

• Proceedings of the KIPE Conference
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• 2001.10a
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• pp.708-712
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• 2001

A new phase-shifted parallel-input/series-output (PI SO) dual inductor-fed push-pull converter for high-power step­up applications is proposed. This converter is operated at a constant duty cycle and employs an auxiliary circuit to control the output voltage with a phase-shift between the two modules. It features a voltage conversion characteristic which is linear to changes in the control input, and high step-up ratio with a greatly reduced switch turn-off stress resulting in a significant increase in the converter efficiency. It also shows a low ripple content and low root-mean-square (RMS) current in the output capacitor. The operational principle is analyzed and a comparative analysis with the conventional pulse-width-modulated (PWM) PISO dual inductor-fed push-pull converter is presented. A 50kHz, 800W, 350Vdc prototype with an input of 20-32Vdc has also been constructed to validate the proposed converter. The proposed converter compares favorably with the conventional counterpart and is considered well suited to high-power step-up applications.

• Journal of Power Electronics
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• v.16 no.4
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• pp.1469-1482
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• 2016

In hybrid energy storage systems, supercapacitors are usually connected in series to meet the required voltage levels. Equalizers are effective in prolonging the life of hybrid energy storage systems because they eliminate the voltage imbalance on cells. This study proposes a modularized equalizer, which is based on a combination of a half-bridge inverter, an inductor, and two auxiliary capacitors. The proposed equalizer inherits the advantages of inductor-based equalization systems, but it also offers unique merits, such as low switching losses and an easy-to-use control algorithm. The zero-voltage switching scheme is analyzed, and the power model is established. A fixed-frequency operation strategy is proposed to simplify the control and lower the cost. The switching patterns and conditions for zero-voltage switching are discussed. Simulation results based on PSIM are presented to verify the validity of the proposed equalizer. An equalization test for two supercapacitor cells is performed. An experimental hybrid energy storage system, which consists of batteries and supercapacitors, is established to verify the performance of the proposed equalizer. The analysis, simulation results, and experimental results are in good agreement, thus indicating that the circuit is practical.

• Proceedings of the KIEE Conference
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• 1992.07b
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• pp.911-914
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• 1992

We have investigated the micro-discharge in plasma display panel using 2 dimensional 2 fluid MHD equations. Plasma display utilizes the physical phenomena of the normal glow or abnormal glow and is considered to be able to provide the largest display area among various flat panel. 2 fluid, 2 dimensional Magneto-Hydro-Dynamic equations are applied to Computational field of 100${\times}$800${\mu}m^2$. Time varing glows and after-glows were investigated for 11 $\mu$sec. We obtained the distribution of the microscopic variables such as the density, temperature, velocity of Ne+Ar0.1% gas plasma. During the first 6$\mu$ sec, glow discharge dued to DC pulse was investigated. Time varing phenomena of after-glow was also investigated during the last 5 $\mu$set. From results, it was found that the driving efficiency of a DC Plasma Display Panel could be improved when the diffusion of ions and electrons are controlled by the pulses applied to the auxiliary anode.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.8
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• pp.1207-1214
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• 2017

In the case of frequent braking, when driving downhill or long distance, conventional brakes using friction are problematic in braking safety due to brake rupture and fading phenomenon. Therefore auxiliary brakes is essential for heavy vehicles. And several research has been actively conducted to improve energy efficiency by regenerating mechanical energy into electric energy when the vehicles brake. In this paper, a voltage control method is utilized to recover the electric energy generated in the electromagnetic retarder instead of the eddy current. To regenerate the braking energy into the electrical energy, a resonant L-C circuit is configured in the retarder. The retarder can be modeled as self-excited induction generator due to its operating principle. The driving conditions according to the retarder's parameters are made into 3-D maps. Also, the voltage of the resonant circuit changing depending on the driving pulse applied to the FET was analyzed. For the control of this voltage, we proposed an algorithm using the PI controller. The controlled voltage is converted by a 3-phase AC/DC converter and then charged to a battery inside the heavy vehicles through a DC/DC converter. Electromagnetic retarder and its controller are validated using Matlab Simulink. We also demonstrate the voltage controller through the actual M-G set experiment.

• Proceedings of the KIEE Conference
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• 2001.07b
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• pp.946-949
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• 2001

This paper proposes a new zero-current switching (ZCS) pulse-width modulation (PWM) switch cell that has no additional conduction loss of the main switch. In this cell, the main switch and the auxiliary switch turn on and turn off under zero current condition. The diodes commutate softly and the reverse recovery problems are alleviated. The conduction loss and the current stress of the main switch are minimized, since the resonating current for the soft switching does not flow through the main switch. Based on the proposed ZCS PWM switch cell, a new family of dc to dc PWM converters is derived. The new family of ZCS PWM converters is suitable for the high power applications employing IGBTs. Among the new family of dc to dc PWM converters, a boost converter was taken as an example and has been analyzed. Design guidelines with a design example are described and verified by experimental results from the 2.5 kW prototype boost converter operating at 40kHz.

• Journal of Power Electronics
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• v.10 no.1
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• pp.27-33
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• 2010

This paper presents a bidirectional DC-DC converter suitable for low-voltage super capacitor-based electric energy storage systems. The DC-DC converter presented here consists of a full-bridge circuit and a current-fed push-pull circuit with a high frequency (HF) transformer-link. In order to reduce the device-conduction losses due to the large current of the super capacitor as well as unnecessary ringing, synchronous rectification is employed in the super capacitor-charging mode. A wide range of voltage regulation between the battery and the super capacitor can be realized by employing a Phase-Shifting (PS) Pulse Width Modulation (PWM) scheme in the full-bridge circuit for the super capacitor charging mode as well as the overlapping PWM scheme of the gate signals to the active power devices in the push-pull circuit for the super capacitor discharging mode. Essential performance of the bidirectional DC-DC converter is demonstrated with simulation and experiment results, and the practical effectiveness of the DC-DC converter is discussed.

• The Transactions of the Korean Institute of Power Electronics
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• v.15 no.6
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• pp.432-440
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• 2010

In this paper, a LC series resonant boost converter using a single switch is proposed. The proposed topology contains additional passive elements in the conventional boost converter and performs Zero Voltage Switching(ZVS) without an additional auxiliary switch when a main switch turned on and off. The switch off time of the proposed system determined by LC series resonance, thus a on-time variable Pulse Frequency Modulation(PFM) method is adapted to control output voltage in the proposed converter. Operational modes of the proposed topology are divided with respected to the current conduction paths and then through the theoretical analysis and experimental results, operational modes and characteristics of the proposed converter are verified.

• Information and Communications Magazine
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• v.32 no.8
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• pp.62-68
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• 2015

본고에서는 차세대 보안통신 기술로 주목 받고 있는 양자암호시스템의 핵심 모듈인 단일광자 검출기의 최신 연구동향과 KIST 연구개발 내용에 대해 기술한다. 현재 상용화 수준으로까지 발전한 유선 양자암호 시스템에서는 성능, 소형화, 가격 등의 장점으로 인해 주로 InGaAs/InP avalanche photo diode (APD)를 이용한 단일광자검출기가 사용되고 있다. 유선 양자암호에서 사용하는 1550nm 통신 파장대의 단일광자가 갖는 에너지는 0.8 eV로 매우 미약한 수준이기 때문에 신호 검출을 위해 APD소자를 내부 증폭 이득이 무한대인 가이거모드(Geiger mode)에서 동작시킨다. 매우 높은 증폭비는 신호 검출뿐만 아니라 노이즈에도 동일하게 영향을 미치기 때문에 주변환경 노이즈에 의한 검출기 오동작 문제가 심각하게 발생한다. 따라서 단일광자검출기 구현에서 가장 중요한 기술은 소자 및 검출기 모듈에서 발생하는 노이즈의 영향을 최소화 시켜주는 것이다. 전세계적으로 검출기의 대표적인 노이즈인 after pulse를 저감 시키기 위한 연구가 매우 활발히 이루어지고 있는데 대표적으로 self-differencing, auxiliary signal, integrating, double balanced 등의 방법이 제시되고 있다. 본고에서는 각각의 최신 기술들에 대한 비교 분석 및 이를 바탕으로 현재 KIST에서 진행하고 있는 양자암호시스템을 위한 단일광자검출기 기술 개발에 대해 서술한다.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.49 no.1
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• pp.1-8
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• 2000

Switched reluctance motor(SRM) has simple magnetic structure, and requires simple power electronic driving circuit. It is very useful for wide range adjustable speed drive system. But, SRM drive generates large vibration and acoustic noise because it is commutated individually by step pulse m.m.f of each phase pole. In the vibration and acoustic noise characteristics. The considerable vibration and noise is induced by radial deforming of stator, so the frequency of dominant vibration and noise is coincident with the frequency of natural mode frequency of mechanical structure. This radial vibration force is generated in the phase commutation region. This paper suggests the new electromagnetic structure of SRM with auxiliary commutation winding which is excited by direct current. This phase and commutation winding are coupled magnetically between one phase winding and the other. Therefore, the switch-off phase current is absorbed by the another phase winding. By this interaction of phase and commutation winding in commutation mechanism, vibration and noise is reduced. And this reduction effect is examined by the test of prototype machine. As a result, SRM with DC exciting commutation winding is very useful to reduce vibration and acoustic noise.