• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.6
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• pp.1007-1012
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• 2016

Induction motors are used widely in driving load of a fluid, such as a pump or a fan in the industry. Induction motor has been generated the voltage drop by the occurrence of a high current during startup. In addition, high start-up current can act as a mechanical stress on the shaft of the motor. So there is need a way to reduce the starting current. Soft start method is one of the many ways to reduce the starting current. This method uses silicon-controlled rectifiers(SCRs) for varying value of the voltage applied to the motor. There is a case for fixing or changing the thyristor firing angle to adjust the magnitude of the voltage. Starting power factor of induction motor is very low compared to the normal operation. Soft starting with the firing angle fixed needs to be considered a low power factor at startup. In this study, we compared the direct start characteristics and soft start characteristics considering the low power factor at the time of start-up. It was possible to confirm that the starting current and the voltage drop is present differently according to the firing angle.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.1
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• pp.103-107
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• 2016

In general, the voltage stability of induction generator is lower than synchronous generator. Induction generator has a number of advantages over the synchronous generator on the side of price and maintenance. So Induction generator has been applied to the small hydroelectric power of low output. Induction generator usually generates a high current during grid connection. The high current that occurs during grid connection can cause a voltage drop in the system. In order to increase the supply of the induction generator, it is necessary to propose a method of reducing high current. This paper proposes some method of the soft start to reduce voltage drop caused by the large starting current. soft-start method has high voltage drop effect than direct start method, control of firing angle can be increased the voltage drop effect.

• Proceedings of the KIPE Conference
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• 2003.11a
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• pp.230-233
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• 2003

Simulation model of induction type fixed speed wind power generator is developed. It is shown that the peak value of inrush current during start up changes according to the firing angle control strategy of soft starter. New proposed firing angle control scheme showed $25\%$ of reduction of peak current which results in smaller drop of gird voltage at the point of common coupling during start up.

• Journal of Power Electronics
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• v.18 no.6
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• pp.1720-1728
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• 2018

This paper proposes a novel soft starting algorithm by using PWM inverter technique to control an amplitude of the motor starting current at a single-phase induction motor (SPIM). Traditional SPIM starting methods such as a Split-Phase, Capacitor-Start, Permanent-Split Capacitor (PSC), Capacitor-Start Capacitor-Run (CSCR), basically cannot control the magnitude of starting current due to the fixed system structures. Therefore, in this paper, a soft starting algorithm based on a proportional resonant (PR) control with a variable and constant frequency is proposed to reduce the inrush current and starting up time. In addition, a transition algorithm for operation modes is devised to generate a constant voltage and constant frequency (CVCF). The validity and effectiveness of the proposed soft starting method and transition algorithm are verified through experimental results.

• Journal of IKEEE
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• v.22 no.2
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• pp.258-265
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• 2018

This paper proposes an algorithm for reducing the starting current when the single-phase induction motor starts and analyzes its operation. Generally, the single-phase induction motors require several starters to generate the starting torque due to their structural characteristics. In this paper, a capacitor-start / capacitor-run method of the single-phase induction motor is basically adopted. This conventional method is efficient and has a large starting torque, but it generates about 5 ~ 6 times of inrush current at startup. As a result, the freezer starting device and peripheral devices are damaged and life time may be reduced. To reduce the inrush current, the current control algorithm based on the virtual dq model is presented to control the starting current. In addition, it validates the proposed algorithm through experiments to smooth transit from start-up operation to the rated operating region.

• Journal of Power Electronics
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• v.16 no.3
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• pp.915-924
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• 2016

A digital self-sustained phase shift modulation (DSSPSM) strategy that allows for good soft switching and dynamic response performance in the presence of step variations is presented in this paper. The working principle, soft switching characteristics, and voltage gain formulae of a LLC converter with DSSPSM have been provided separately. Furthermore, the method for realizing DSSPSM is proposed. Specifically, some key components of the proposed DSSPSM are carefully investigated, including a parameter variation analysis, the start-up process, and the zero-crossing capture of the resonant current. The simulation and experiment results verify the feasibility of the proposed control method. It is observed that the zero voltage switching of the switches and the zero current switching of the rectifier diodes can be easily realized in presence of step load variations.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.64 no.6
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• pp.885-890
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• 2015

LLC resonant converter has been widely used because of its high efficiency and high energy density. In this paper, we designed a LLC resonant converter as the main power supply of the Nd:YAG pulse laser. First harmonic approximation (FHA) is used to model the LLC resonant converter. FHA equivalent circuit model and the transfer function of the LLC resonant converter is proposed. Soft start technology is also used to suppress the surge current. The laser output simulation test result is identical with the practical test, the laser energy of every pulse can reach up to 2.5J, and the pulse per second (PPS) can be adjusted from 6 to 18. The power system is verified stable and reliable by both of the simulation and experiment results.

• Proceedings of the KIPE Conference
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• 2006.06a
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• pp.43-45
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• 2006

대부분의 컨버터들은 초기 기동시에 MOSFET 전류와 전압의 과도한 상승을 막아주기 위해서 Soft Start 기능을 갖고 있다. 하지만 제어기 내부의 지연시간이나 LEB(Leading Edge Blanking) 시간 등으로 인해 MOSFET은 무시할 수 없는 상당한 기간의 최소 턴온 시간(Minimum Turn-on Time)을 갖게 되고, 이로 인해 드레인 전류가 과도하게 상승하는 현상을 보이게 된다. 본 논문에서는 이런 현상이 발생할 수 있는 초기 기동이나 출력단 단락시에 과도한 드레인 전류의 상승을 막아주는 방법을 제시하고자 한다.

• Journal of IKEEE
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• v.24 no.1
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• pp.319-325
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• 2020

In this paper, a discontinuous-conduction mode (DCM) DC-DC buck converter is presented for mobile device applications. The buck converter consists of compensator for stable operations, pulse-width modulation (PWM) logic, and power switches. In order to achieve small hardware form-factor, the number of off-chip components should be kept to be minimum, which can be realized with simple and efficient frequency compensation and digital soft start-up circuits. Burst-mode operation is included for preventing the efficiency from degrading under very light load condition. The DCM DC-DC buck converter is fabricated with 0.18-um BCDMOS process. Programmable output with external resistors is typically set to be 1.8V for the input voltage between 2.8 and 5.0V. With a switching frequency of 1MHz, measured maximum efficiency is 92.6% for a load current of 100mA.

• Journal of Korea Multimedia Society
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• v.19 no.2
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• pp.352-359
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• 2016

This paper presents high efficiency 5A synchronous DC-DC buck converter. The proposed DC-DC buck converter works from 4.5V to 18V input voltage range, and provides up to 5A of continuous output current and output voltage adjustable down to 0.8V. This chip is packaged MCP(multi-chip package) with control chip, top side P-CH switch, and bottom side N-CH switch. This chip is designed in a 25V high voltage CMOS 0.35um technology. It has a maximum power efficiency of up to 94% and internal 3msec soft start and fixed 500KHz PWM(Pulse Width Modulation) operations. It also includes cycle by cycle current limit function, short and thermal shutdown protection circuit at 150℃. This chip size is 2190um*1130um includes scribe lane 10um.