• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.7 no.1
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• pp.26-35
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• 1996

In this paper, characteristics of the electromagnetically coupled broadband microstrip antennas are analyzed by the Finite Difference Time Domain (FDTD) method, and antenna para- meters are optimized to get maximum bnadwidth. By using short radial tuning stub in microstrip feedline, electromagnetically coupled microstrip antenna shows broadband ($\simeq$13%) characteristics, and the characteristics are varied as a function of radius, radial angle, and position of the radial tuning stub. Operating frequency, return loss, VSWR and input impedance are calculated by Fourier transforming the time domain results. After optimization of the parameters, maximum bandwidth of the radial stub tuning microstrip antenna is about 15% and the ripple char- acteristic of the VSWR is better than the rectangular tuning stub microstrip antenna.

• The Transactions of the Korean Institute of Power Electronics
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• v.13 no.6
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• pp.447-452
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• 2008

In the paper, the product-type PLL system, which is so suitable for synchronizing a single phase grid voltage is designed. The PLL system is modelled with the small signal analysis. Both the cut-off frequency of low pass filter and the optimal gain are derived by considering the transient response for synchronization as well as a distortion of synchronization signal. Through the simulation studies and experimental results, the transient response and ripple component of synchronization signal are investigated with a variation of both the cut-off frequency and gain in order to verify the performance of design.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.49 no.12
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• pp.813-820
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• 2000

A technique to suppress the low frequency ripple voltage of the DC output in three phase buck diode converter is presented in this paper. The proposed pulse frequency modulation methods and duty ratio modulation methods are employed to regulate the output voltage of the buck diode converter and guarantee zero-current-switching(ZCS) of the switch over the wide load range. The proposed control methods used in this paper provide generally good performance such as low THD of the input line current and unity power factor. In addition, control methods can be effectively used to suppress the low frequency ripple voltage appeared in the dc output voltage. The harmonic injection technique illustrates its validity and effectiveness through the simulations and experiments.

• The Proceedings of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.6 no.2
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• pp.56-61
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• 1992

This paper is reported on the simulation and test results of a constant flux vector control scheme of an induction motor without any speed detecting eqiupment, in which the adaptive current PWM inverter is used. The rotor speed is estimated form stator voltage, current and parameters of motor, and control algorithm in the system is performed with by micro processor. By comparing the waveform of input current of this system with that of the case with taco-generator, good agreement is observed except small ripple component. Experimental results which are acquired at start up and during acceleration/deceleration are quite similar to those of the simulation results.

• Journal of IKEEE
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• v.20 no.3
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• pp.314-317
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• 2016

Recently, efforts to maximize battery life in progress with an increase in the demand for portable devices. In this paper, we propose multi-phase buck converter with fast transient response. Multi-phase buck converter may be used for the output capacitor of small size because the ripple cancellation effect, it is possible to use an inductor having an inductance less. The portable device for quick change from standby mode to active 4-phase design structure was given a fast transient response. The proposed multi-phase buck converter was fabricated using a 0.18 um CMOS process and the supply voltage ranges from 2.7V to 3.3V, the maximum load current is 500mA and settling time is 10us.

• Journal of IKEEE
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• v.20 no.3
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• pp.318-321
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• 2016

As IoT industry are growing fast, The importance of power management system is also being magnified. CMOS High power-supply rejection ratio(PSRR) Low-dropout(LDO) regulator is achieved by the proposed ripple Subtractor, Feed-forward capacitor and OTA in this paper. The LDO is implemented in $0.18-{\mu}m$ CMOS technology. With the proposed structures, in the maximum loading of 40mA, Simulation result achieves PSRR of -73.4dB at 500kHz and PSRR better than -40dB when frequency is below 10MHz with $6.8-{\mu}F$ output capacitor.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.12 no.1
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• pp.93-102
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• 1998

This paper describes to control system for AC to DC converter which has been widely used to power source in industrial factory and domestics. In this paper, three-phase PWM AC to DC Boost converter that operates with unity power factor and sinusodial input line currents is presented. The current control of this converter is based on the predicted current control strategy with fixed switching frequency and the line currents track to reference currents within one sampling time interval. By using this control strategy low ripples in the output current and the voltage as well as fast dynamic response are achieved with small dc link capacitance employed.ployed.

• Proceedings of the KIPE Conference
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• 2015.07a
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• pp.345-346
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• 2015

본 논문은 30kW, 95GHz 자이로트론을 구동하기 위한 50kV, 100kW 출력의 Cathode Power Supply(CPS) 설계에 대해 기술한다. 자이로트론 구동 시스템의 신뢰성과 효율성 향상을 위해 고효율 공진형 컨버터 토폴로지를 이용한 3개의 컨버터 모듈을 기반으로 출력단이 직렬로 구성된 모듈의 3상 운전을 통해 낮은 출력 전압 리플과 함께 아크 발생 시 부하 단으로 전달되는 에너지를 최소화 할 수 있도록 CPS를 설계한다. 또한 고전압 전원장치의 절연에 대한 신뢰성 확보와 전력밀도 향상을 위한 변압기 및 정류부의 효율적인 절연 설계 및 구현에 대하여 기술한다. 설계된 CPS의 실험결과를 통해 30kW, 95GHz 자이로 트론을 구동하기 위한 전원장치 설계의 타당성과 우수성을 검증한다.

• The Transactions of the Korean Institute of Power Electronics
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• v.26 no.5
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• pp.342-348
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• 2021

The PV module of solar power systems requires maximum power point tracking (MPPT) technique because the power-voltage and current-voltage characteristics vary depending on the surrounding environment. In addition, the 120 Hz ripple voltage on the DC-Link is caused by the imbalance of the system voltage and current. The effect of this 120 Hz ripple voltage reduces the efficiency of the power generation system by increasing the output current distortion rate. Increasing the capacity of DC-Link can reduce the 120 Hz ripple voltage, but this method is inefficient in price and size. We propose a technique that detects 120 Hz ripple voltage and reduces the effect of ripple voltage without increasing the DC-Link capacity through a controller. The proposed technique was verified through simulations and experiments using a 1 kW single-phase solar power system. In addition, the proposed technique's feasibility was demonstrated by reducing the distortion rate of the output current.

• Journal of IKEEE
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• v.23 no.2
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• pp.407-412
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• 2019

Many industrial regions has used and extended the application of LED driver because of many advantage. Specially, due to the simplicity, miniaturization and power density, the flyback converter is selected by a lot of power engineer. Also, the electrolytic capacitor in this converter is used for the constant DC voltage of the converter because of the sufficient capacitance and the economic price. However, because of the characteristics of the electrolytic capacitor and ripple currents on the converter. the expected lifetime of the LED driver is more and more shorted. In this paper, a single-stage CCM PFC flyback converter with the film capacitor is suggested to extended the lifetime of the LED driver. In addition, the proposed converter with the LC filter is decreased the ripple current of the converter output.