• Proceedings of the KIPE Conference
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• 1998.10a
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• pp.316-319
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• 1998

RPWM(Random Pulse Width Modulation) is a switching technique to spread the voltage and current harmonics on the wide frequency area. Using randomly changed switching frequency of the inverter, the power spectrum of the electromagnetic acoustic noise cab be spread to the wide-band area. The wide-band noise is much more comfortable and less annoying than the narrow-band one. So RPWM have been attracting an interest as an excellent method for the reduction of acoustic noise on the inverter drive system. In this paper a new RPPWM (Random Position PWM) is proposed and implemented. Each of three pulses is located randomly in each switching interval. Along with the randomization of PWM pulses, the space vector modulation is executed in the C167 microcontroller also. The experimental results show that the voltage and current harmonics were spread to wide band area and that the audible switching noise was reduced by proposed RPPWM method.

• Proceedings of the KIEE Conference
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• 1997.07b
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• pp.471-473
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• 1997

In this paper, We propose a variable structure controller with time varying switching surface. We calculate the maximum value of switching surface gradient under the bound of input. To enhance the robustness, we, choose a time varying switching surface gradient that is of the 3rd order polynominal form. We use evolution strategy to optimize the parameters of the switching surface gradient. Finally, the proposed method is applied to the motor position control. Simulation results show that the proposed method is more useful than the conventional variable structure controller.

• 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.41 no.8
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• pp.902-913
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• 1992

There have been several control schemes for the single input systems with unmeasurable state variables using variable structure control(VSC) theory. In the previous VSC, the systems must be represented in phase canonical form and the complete measurements for each state variable must be assumed. In order to eliminate these restrictions several VSC methods were proposed. And especially for the systems in phase canonical form with unmeasurable state variables, the reduced order switching function algorithm was proposed. But this method has many drawbacks and can not be used in the case of general form (not phase canonical form) dynamic system. Therefore this paper propose new construction method of switching fuction for the systems in phase canonical form, which reduce the restriction of reduced order switching function algorithm. And this algorithm can be realized for any state representation and adopted in the systems where not all states are available for switching function synthesis or control.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.43 no.5
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• pp.761-769
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• 1994

VCB (Vacuum Circuit Breaker), with the strong arc extinction capability in switching the source of an induction motor, occurs the severe switching surge voltage which can cause the breakdown or the deterioration of motor insulation. Therefore, a method which reduces surge voltage across motor windings is necessary. So, it is analyzed that fast-rise-time surges resulting from VCB switching operations give rise to severe voltage stress on turn insulation. Additionally, the switching surge simulation algorithms using EMTP are developed, and C, R values of surge suppressor minimizing the steep-fronted stress in winding insulation surges are calculated.

• Journal of the Optical Society of Korea
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• v.5 no.2
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• pp.39-42
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• 2001

A new method of switching mode in AFLC cell is proposed for faster switching time and higher contrast ratio. In this mode the ″dark″ state is obtained by applying negative full voltage while the ″bright″ state is achieved by applying positive full voltage to the cell. The switching time is reduced to 100 $mutextrm{s}$ for the cell whose switching time is 22 ms when operated in conventional mode. The contrast ratio is also improved vastly with this method. The possibility of achieving gray scale was shown in this mode of operation.

• Journal of the Microelectronics and Packaging Society
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• v.15 no.1
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• pp.59-64
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• 2008

Recently, DC-DC choppers must be increased switching frequency in order to achieve a small size, a light weight and a low noise. However, the switches of chopper are subjected to high switching power losses and switching stresses. As a result of these, the chopper system bring on a low power efficiency. To improved these, this paper is studied on a new DC-DC chopper of high efficiency operated with soft switching(that is, zero current switching and zero voltage switching, ZVCS), of semiconductor switches using in chopper. The soft switching operation is applied to a partial resonant method that the switches operate at zero current of inductor and zero voltage of capacitor in resonant circuit. And the partial resonant circuit makes use of a inductor using step-up and a snubber capacitor, the circuit topology of chopper is simple. Some simulative results on computer and experimental results confirm the validity of analytical results of the DC-DC chopper.

• Journal of Preventive Medicine and Public Health
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• v.52 no.4
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• pp.258-264
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• 2019

Objectives: The perceptions of family-planning (FP) acceptors regarding contraception influence the reasons for which they choose to switch their method of contraception. The objective of this study was to analyze the perceptions of contraception and rationales for switching contraceptive methods among female FP acceptors in West Nusa Tenggara, Indonesia. Methods: This study involved the analysis of secondary data from the Improve Contraceptive Method Mix study, which was conducted in 2013 by the Center for Health Research, University of Indonesia. The design of the study was cross-sectional. We performed 3 stages of sampling using the cluster technique and selected 4819 women who were FP acceptors in West Nusa Tenggara Province, Indonesia as the subjects of this study. The data were analyzed using multiple logistic regression. Results: The predominant pattern of switching contraceptive methods was switching from one non-long-term method of contraception to another. Only 31.0% of the acceptors reported a rational pattern of switching contraceptive methods given their age, number of children, and FP motivations. Perceptions of the side effects of contraceptive methods, the ease of contraceptive use, and the cost of the contraceptives were significantly associated (at the level of ${\alpha}=0.05$) with rational patterns of switching contraceptive methods. Conclusions: Perceptions among FP-accepting women were found to play an important role in their patterns of switching contraceptive methods. Hence, fostering a better understanding of contraception through high-quality counseling is needed to improve perceptions and thereby to encourage rational, effective, and efficient contraceptive use.

• 제어로봇시스템학회:학술대회논문집
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• 1986.10a
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• pp.547-549
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• 1986

This paper deals with large scale distributed packet switching system which is modeled by state space form and optimizing routing algorithms and buffer size via a hierachical system optimization method, the interaction prediction method.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.14 no.7
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• pp.590-594
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• 2001

The residual DC properties in the in-plane switching (IPS) liquid crystal displays(LCDs) which have different concentrations of cynao NLCs and different resistivities of fluorine NLCs were studied. We also propose a new residual DC measurement method, named 'light minimum/maximum method'. We confirmed the precision of residual DC measurement by light minimum/maximum method compared with the flicker minimizing method and found that new measurement method of residual DC is more accurate than that of the conventional flicker minimizing method since the resolution level of measurements is in 0.1V.