• The Transactions of the Korean Institute of Electrical Engineers B
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• v.55 no.4
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• pp.231-237
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• 2006

This paper proposes an effective drive of high intensity discharge (HID) lamp ballast for cars. All control functions of the proposed ballast are implemented using a low-cost single chip microcontroller, PIC16C73 to optimize the total system size and to minimize cost through minimization of total component number. The proposed ballast generates high open-circuit voltage to ignite the lamp and is controlled to supply effectively the power required to shorten warm-up period after the breakdown. The DC-DC converter of the DC-AC converter part of the ballast utilizes the flyback converter topology that can minimize component number. Also, because to more minimize the ballast size, the transformer size must be minimized, for this, PWM (Pulse Width Modulation) pulses are generated with high frequency using the PWM module of the microcontroller. An analysis for this is explained, briefly. As if the operation of the lamp and ballast arrives at steady-state, then the ballast must AC-control the lamp, for this, the microcontroller utilizes the other PWM module. And the part related to the igniter is explained, briefly. It is shown through experimental results that the controller of the proposed ballast has good performance for the HID lamp for cars.

• Journal of Power Electronics
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• v.10 no.4
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• pp.342-350
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• 2010

Randomizing the switching frequency (RSF) to reduce the electromagnetic interference (EMI) of switching power converters is a well-known technique that has been previously discussed. The randomized pulse position (RPP) technique, in which the switching frequency is kept fixed while the pulse position (the delay from the starting of the switching cycle to the turn-on instant within the cycle) is randomized, has been previously addressed in the literature for the same purpose. This paper presents a double-hybrid technique (DHB) for EMI reduction in dc-dc switching regulators. The proposed technique employed both the RSF and the RPP techniques. To effectively spread the conducted-noise frequency spectrum and at the same time attain a satisfactory output voltage quality, two parameters (switching frequency and pulse position) were randomized, and a third parameter (the duty ratio) was controlled by a digital compensator. Implementation was achieved using field programmable gate array (FPGA) technology, which is increasingly being adopted in industrial electronic applications. To evaluate the contribution of the proposed DHB technique, investigations were carried out for each basic PWM, RPP, RSF, and DHB technique. Then a comparison was made of the performances achieved. The experimentally investigated features include the effect of each technique on the common-mode, differential-mode, and total conducted-noise characteristics, and their influence on the converter’s output ripple voltage.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.3A
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• pp.319-323
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• 2007

In this paper, the automatic precision measurement of RF voltage has been done using the power and impedance standards [1] in the frequency range of 50 to 1000 MHz. A coaxial microcalorimeter and an automatic network analyzer were used for the determination of the RF-DC differences and the total uncertainty is about 1.0 %. A HP computer, a commodore computer and IEEE-488 interface bus were used for measuring the effective efficiency of thermistor mount and the RF-DC difference of thermal voltage converter, All processes of measurement were accomplished by self-developed program automatically.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.52 no.12
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• pp.632-640
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• 2003

In conventional Zero-Voltage-Transition(ZVT) PWM converters, zero-voltage turn-on and turn-off for main switch without increasing voltage/current stresses is achieved at a fixed frequency. The switching loss, stress, and noise, however, can't be minimized because they adopt auxiliary switches turned off under hard-switching condition. In this paper, new ZVS-PWM converters of which both active and passive switches are always operating with soft-switching condition are proposed. Therefore, the proposed ZVS-PWM converters are most suitable for avionics applications requiring high-power density. Breadboarded ZVS-PWM boost converters using power MOSFET are constructed to verify theoretical analysis.

• Journal of Power Electronics
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• v.16 no.2
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• pp.522-531
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• 2016

This paper proposes a new NLC (Nearest Level Control) scheme for MMCs (Modular Multilevel Converters), which offers voltage ripple reductions in the DC capacitor of the SM (Sub-Module), the output voltage harmonics, and the switching losses. The feasibility of the proposed NLC was verified through computer simulations. Based on these simulation results, a hardware prototype of a 10kVA, DC-1000V MMC was manufactured in the lab. Experiments were conducted to verify the feasibility of the proposed NLC in an actual hardware environment. The experimental results were consistent with the results obtained from the computer simulations.

• Proceedings of the KIEE Conference
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• 1996.07a
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• pp.395-399
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• 1996

The Clamp Mode(CM) Forward Zero Voltage Switching Multi Resonant Converter(ZVS-MRC) with self-driven synchronous rectifier in studied. The loss at the synchronous rectification stage of the converter is analyzed using MOSFET linear model and is compared with the loss at the conventional schottky diode rectification stage of the converter. From the results of the analysis, it is known that the use of MOSFETs as a synchronous rectifier reduces the loss at the rectification stage over the whole load range comparing the use of schottky diodes as a conventional rectifier in the converter. In order to verify the validity of the analysis, we have built a 33W(3.3V/10A) CM Forward ZVS-MRC with self-driven synchronous rectifier, in which switching frequency is 1MHz, and tested. From the experimental results, it is known that the synchronous rectification achieved about 1W improvement in the loss at the rectification stage and about 3% in the efficiency at the converter as compared with the conventional schottky diode rectification.

• The Transactions of the Korean Institute of Power Electronics
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• v.24 no.4
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• pp.259-267
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• 2019

An active clamp flyback (ACF) converter applies a clamp circuit and circulates the energy of leakage inductance to the input side, thereby achieving a zero-voltage switching (ZVS) operation and greatly reducing switching losses. The switching losses are further reduced by applying a gallium nitride field effect transistor (GaN-FET) with excellent switching characteristics, and ZVS operation can be accomplished under light load with boundary conduction mode (BCM) operation. Optimal design is performed on the basis of loss analysis by selecting magnetization inductance based on BCM operation and a clamp capacitor for loss reduction. Therefore, the size of the reactive element can be reduced through high-frequency operation, and a high-efficiency and high-power-density converter can be achieved. This study proposes an optimal design for a high-efficiency and high-power-density BCM ACF converter based on GaN-FETs and verifies it through experimental results of a 65 W-rated prototype.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.1
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• pp.129-134
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• 2014

This paper presents a 10-bit 10-MS/s asynchronous successive approximation register (SAR) analog-to-digital converter (ADC) which consists of a digital-to-analog converter (DAC), a SAR logic, and a comparator. The designed asynchronous SAR ADC with a rail-to-rail input range uses a binary weighted DAC using metal-oxide-metal (MOM) capacitor to improve sampling rate. The proposed 10-bit 10-MS/s asynchronous SAR ADC is fabricated using a 0.18-${\mu}m$ CMOS process and its active area is $0.103mm^2$. The power consumption is 0.37 mW when the voltage of supply is 1.1 V. The measured SNDR are 54.19 dB and 51.59 dB at the analog input frequency of 101.12 kHz and 5.12 MHz, respectively.

• 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 KIEE Conference
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• 1997.07f
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• pp.2155-2158
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• 1997

This paper describes the performance improvement of dc TIG (Tungsten Inert Gas) welder. The TIG welder consists of single phase full bridge IGBT inverter which incorporates the high frequency transformer, the boost converter for improving the input power factor, and the arc start system. The arc will be generated without fail even when the extension cable between the torch and the power source is 100m long. In addition, the arc start system with a short dc output voltage will generate less EMI noise than the traditional arc start system with a high frequency output voltage. To demonstrate the practical significance of the proposed methods, some simulation studies are presented.