• The Transactions of the Korean Institute of Power Electronics
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• v.11 no.2
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• pp.142-148
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• 2006

In this paper, authors propose a novel step-up AC-DC converter operated with power factor correction (PFC) and with high efficiency. The proposed converter behaves with discontinuous current control (DCC) of input current. The input current waveform in the proposed converter is got to be a discontinuous sinusoid form in proportion to magnitude of at input voltage under the constant duty cycle switching. Therefore, the input power factor is nearly unity and the control method is simple. In the general DCC converters, the switching devices are turned-on with the zero current switching (ZCS). But turn-off of the switching devices is done at the maximum current. To achieve a soft switching at turn-off, the proposed converter uses a new partial resonant circuit, which results in the very low switching loss and the high efficiency of converter.

• Journal of Communications and Networks
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• v.4 no.2
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• pp.128-135
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• 2002

We propose a new space priority mechanism, and analyze its performance in a single Constant Bit Rate (CBR) server. The arrival process is derived from the superposition of two types of traffics, each in turn results from the superposition of homogeneous ON-OFF sources that can be approximated by means of a two-state Markov Modulated Poisson Process (MMPP). The buffer mechanism enables the Asynchronous Transfer Mode (ATM) layer to adapt the quality of the cell transfer to the Quality of Service (QoS) requirements and to improve the utilization of network resources. This is achieved by "Selective-Delaying and Pushing-ln"(SDPI) cells according to the class they belong to. The scheme is applicable to schedule delay-tolerant non-real time traffic and delay-sensitive real time traffic. Analytical expressions for various performance parameters and numerical results are obtained. Simulation results in term of cell loss probability conform with our numerical analysis.

• Journal of IKEEE
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• v.25 no.4
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• pp.741-749
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• 2021

This paper presents the current-fed type LLC AC to DC high frequency resonant converter capable of ZVZCS(Zero-Voltage and Zero-Current Switching). The current-fed type LLC AC to DC high frequency resonant converter proposed in this paper could operate not only in ZVS(Zero-Voltage Switching) operation by connecting the resonant capacitors(C₁, C₂) in parallel across the switching devices but also in ZCS(Zero-Current Switching) operation of the secondary diode. The ZVS and ZCS operations can reduce the turn-on loss of the switching devices and the turn-off loss of the secondary diodes, respectively. The circuit analysis of current-fed type LLC AC to DC high frequency resonant converter proposed in this paper is addressed generally by adopting the normalized parameters. The operating characteristics of proposed LLC AC to DC high frequency resonant converter were also evaluated by using the normalized control parameters such as the normalized control frequency(μ), the normalized load resistor(λ) and so on. Based on the characteristic values through the characteristics of evaluation, an example of the design method of proposed LLC AC to DC high frequency resonant converter is suggested, and the validity of the theoretical analysis is confirmed using the experimental results and PSIM simulation.

• Journal of the Korean Institute of Telematics and Electronics B
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• v.33B no.11
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• pp.167-174
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• 1996

For the decreasing of switching loss, this paper designs the improved buck converter circuit and then compare with the conventional buck converter and finally analyzes the performance. When the switch is turn-off, in the buck converter using the smoothing capacitor, the flow of transient current and peak voltage having the high frequency components was generated because of the instantaneous open-state in the teminals of the switch. However, the buck converter presented in this paper eliminated this disadvantage by using the L-C circuit. Therefore, the higher PF in 0.85 is achieved than that of the buck converter using the smoothing capacitor. Also, due to the decreasing of the harmonic contain rate, the current usage rate is to be higher than that of the conventional buck converter by 4.48dB and the output voltage varient rate for the step response is to be lower 1.32 times than that of the conventional buck converter.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.37 no.7
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• pp.442-447
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• 1988

Saturable reactor-resistor pair is proposed as a part of snubber and applied to a hard commutation chopper. SCR turn off process is modeled to simulate the hard commutation chopper. State equations are derived for each mode of the chopper and they are solved by Runge-Kutta 4th order method. It is shown that the reverse voltage spike and reverse dv/dt can be minimized by applying saturable reactor-resistor pair to the chopper which controls peak reverse recovery current and damping factor. Saturable reactor-resistor pair can be used to reduced SCR power loss and value of snubber capacitor and can be applied to high power thyristor devices.

• Proceedings of the KIPE Conference
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• 1997.07a
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• pp.116-123
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• 1997

This paper was described about principle and form of proposed circuit made use of soft switching technology ZVS(Zero Voltages Switching) and ZCS(Zero Current Switching) to reduce turn on and off loss at switching. Also, the analysis of the proposed circuit is described generally by using normalized parameter and basic operating principle and driving characteristics have been evaluated as to switching frequency and load p arameter. Based on the characteristics value, a method of circuit design is proposed. In addition, Pspice's simulation and experimental waveforms are compared with theoretical ones. The experimental results shows that the proposed Inverter can be used practically such as power source system for induction cooker etc.

• Proceedings of the KIPE Conference
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• 2001.10a
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• pp.611-616
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• 2001

This paper analyzed PFC of active clamp ZVS flyback converter by adding two methods PFC (power Factor Correction) circuit - two-stage and single-stage. The addition of active clamp circuit also provides a mechanism for achieving ZVS of both the primary and auxiliary switches. ZVS also limits the turn off di/dt of the output rectifier, reducing rectifier-switching loss and switching noise, due to diode reverse recovery. As a result, the proposed converters have characteristics of the reduced switching noise and high efficiency in comparison to conventional flyback converter. The simulation and experimental results show that the proposed converter improve the input PF of 300W ZVS flyback converter by adding single-stage, two-stage PFC circuit.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.60 no.4
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• pp.246-252
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• 2011

In this paper proposes the soft-switching boost converter and MPPT control for improving the efficiency of PV system. The proposed converter designed H-bridge auxiliary resonant circuit. By this circuit, all of the switching devices perform the soft switching under the zero voltage and zero current condition. Therefore the periodic switching losses can be decreased at turn on, off. The soft switching boost converter designs for 1.5[kW] solar module of the power conversion. Thus, this soft switching boost converter is simulated by MATLAB simulation using Newton-Method algorithm. As a result, Proposed Soft Switching Converter compared to a typical boost converter switching loss was reduced about 61%. And the overall system efficiency was verified to increase about 3.3%.

• Proceedings of the KIEE Conference
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• 2008.11a
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• pp.418-420
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• 2008

The GENCO of competition in the market for profit maximization of business development for the study of how to build a facility plan. The total revenue for this thesis may be deducted from the total cost calculations and the cumulative profit, the result of cumulative profit through the profit and loss, and up to the turn-off to find a generator of canonicalization. Fortran, using a model to formally implement the program, and a graph that displays the results to build any power plants is the most efficient visibility of the eye can see.

• Journal of Power Electronics
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• v.14 no.2
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• pp.265-270
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• 2014

In terms of power loss, a MOSFET has two advantages over an IGBT with an antiparallel diode: purely resistive without an offset voltage in conduction and no tail current at turn-off. However, the reverse recovery characteristic of the body diode is so poor that MOSFETs have not yet been available for high-voltage power converters with bidirectional power flow legs. This paper introduces how MOSFETs can be fully applied to high-voltage power converters with bidirectional power flow legs in order to achieve high efficiency. With a bidirectional DC-DC converter with one leg as the simplest example, the basic circuit topology and operating principle are described in detail. The high efficiency and stable operation of the proposed converter are validated through experiments with a 1.5 kW prototype.