• The Journal of Korean Institute of Communications and Information Sciences
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• v.42 no.4
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• pp.864-870
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• 2017

This paper describes a Dual Buck Converter with mode control using variable Frequency to Voltage for portable devices requiring wide load current. The inherent problems of PLL compensation and efficiency degradation in light load current that the conventional hysteretic buck converter has faced have been resolved by using the proposed Dual buck converter which include improved PFM Mode not to require compensation. The proposed mode controller can also improve the difficulty of detecting the load change of the mode controller, which is the main circuit of the conventional dual mode buck converter, and the slow mode switching speed. the proposed mode controller has mode switching time of at least 1.5us. The proposed DC-DC buck converter was implemented by using $0.18{\mu}m$ CMOS process and die size was $1.38mm{\times}1.37mm$. The post simulation results with inductor and capacitor including parasitic elements showed that the proposed circuit received the input of 2.7~3.3V and generated output of 1.2V with the output ripple voltage had the PFM mode of 65mV and 16mV at the fixed switching frequency of 2MHz in hysteretic mode under load currents of 1~500mA. The maximum efficiency of the proposed dual-mode buck converter is 95% at 80mA and is more than 85% efficient under load currents of 1~500mA.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.4
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• pp.504-510
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• 2017

This paper presents an AC-DC power module design and evaluates its efficiency and reliability when used for electronics appliances. This power module consists of a PWM control IC, power MOSFETs, a transformer and several passive devices. The module was tested at an input voltage of 220V (RMS) (frequency 60 Hz). A test was conducted in order to evaluate the operation and power efficiency of the module, as well as the reliability of its protection functions, such as its over-current protection (OVP), overvoltage protection (OVP) and electromagnetic interference (EMI) properties. Especially, we evaluated the thermal shut-down protection (TSP) function in order to assure the operation of the module under high temperature conditions. The efficiency and reliability measurement results showed that at an output voltage of 5 V, the module had a ripple voltage of 200 mV, power efficiency of 73 % and maximum temperature of $80^{\circ}C$ and it had the ability to withstand a stimulus of high input voltage of 4.2 kV during 60 seconds.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.20 no.1
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• pp.34-40
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• 2006

This paper proposed power system for new DC 49[V] telecommunication using forward three-phase PWM rectifier power factor and efficiency for improvement of ripple voltage. Proposed power system for DC 48[V] telecommunication that consists of power conversion devices including switch, inductor and condenser were made between each line, in power inverter device of each switch control turn-on in period of continuity time control to get power factor '1' of sine wave current and on-off of switch lessens peak current that was happened and got conversion efficiency 92.1[%] composing in PWM rectifier of forward form instead of general PWM rectifier. Also, harmonic input regulation value(IEC61000-3-2 Class-As) satisfy input current and reduce ripple factor of output voltage in state that distortion of three-phase supply is overlapped each other.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.20 no.8
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• pp.54-62
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• 2006

Voltage unbalance will be generated by the load unbalance operation such as combination operation of single & three phase load and current unbalance will be more severe by the deteriorated voltage quality. Under the these unbalance conditions, all power electronic converters used in different types of electronic systems can increase harmonic disturbances by injecting harmonic currents directly into the feeder grid of three phase 4-wire. Harmonic current may cause torque to decrease. it may also overheat or become noisy and torque oscillation in the rotor can lead to mechanical resonance and vibration. This paper presents a scheme on the characteristics of induction motor under the combination of linear & non-linear loads at the three phase 4-wire power distribution system by the unbalance and harmonic components. It was able to confirm that the number of torque pulsation decreased and torque ripple values increased by the harmonics that reduction was difficult by five harmonics filters at additional driving time of single-phase non-linear load.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.45 no.9
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• pp.1-7
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• 2008

This paper proposes 3.3V input and 1.8V output voltage mode step-down DC-DC buck converter for wireless mobile system which is designed in a standard 0.35$\mu$m CMOS process. The proposed capacitor multiplier method can minimize error amplifier compensation block size by 30%. It allows the compensation block of DC-DC converter be easily integrated on a chip. Also, we improve efficiency to 3% using low power buffer. Measurement result shows that the circuit has less than 1.17% output ripple voltage and maximum 83.9% power efficiency.

• The Transactions of the Korean Institute of Power Electronics
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• v.14 no.2
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• pp.120-127
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• 2009

This paper proposes a new Pulse Frequency Modulation(PFM)-Series Boost Capacitor(SBC) full bridge DC/DC Converter which features a high efficiency and high power density. The proposed converter controls the output voltage by varying the voltage across the series boost capacitor according to switching frequency and has no freewheeling period due to 50% fixed duty operation. As a result, its conduction loss is lower than that of the conventional phase shift full bridge converter. Moreover, ZVS of all power switches can be ensured along wide load ranges and output current ripple is very small. Therefore, it has very desirable merits such as a small output inductor, high efficiency, and improved heat generation. This paper performs a rationale and PSIM simulation of the proposed converter. Finally, experimental results from a 1.2kW(12V, 100A) prototype are presented to confirm the operation, validity and features of the proposed converter.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.17 no.1
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• pp.86-93
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• 2003

This paper describes that the resonant tank type DC-DC converter consist of reactor and capacitor resonant tank circuit for increased the output current. This circuit configuration is composed of the resonant tank circuit used resonant capacitor and reactor and the capacitor connected in switch are a common using by resonance capacitor and ZVS(Zero Voltage Switching) capacitor. Therefore, the proposed converter can reduce a switching losses, noise, and voltage stress at turn-on and turn-on and has an advantage which is able to operating safely in load short, because DC reactor is connected with resonance reactor in order to supply a fixed current with low ripple from DC power supply. The analysis of proposed circuit uses normalized parameters and characteristic estimation is generally described the proposed circuit with the characteristics of power and output voltage etc. Also, design is based on the characteristic estmations in each step. Hence, We conform a rightfulness theoretical analysis by comparing a theoretical values and experimental values obtained from experiment.

• The Transactions of the Korean Institute of Power Electronics
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• v.16 no.3
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• pp.209-218
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• 2011

In low voltage high current applications such as fuel cells the current-fed DC-DC converter which has small ripple current and turn ratio is more efficient. In the applications larger than 5kW the conventional single-phase current-fed converter based on full-bridge, half-bridge or push-pull topologies has high current burden of devices such as switches, and the selection and optimized design of the devices are not easy. In this paper a three-phase active-clamped current-fed push-pull DC-DC converter suitable for high power high step-up applications is proposed. The proposed converter has reduced current burden and is suitable for wide input voltage applications due to the use of whole duty cycle range. Design methods of main components including three-phase high frequency transformers are provided, and the validity and performance of the proposed converter are proved from a 5kW prototype.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.10
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• pp.1126-1135
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• 2007

This paper presents the varactor-tuned miniaturized hairpin tunable filter with a single control voltage. The previously proposed miniaturization method is a very straight-forward method to miniaturize a parallel coupled-line filter. In this paper, the miniaturized hairpin tunable filter is proposed with the constant ratio rule of that the capacitances of the each stage always have constant ratio without any dependency to miniaturized electrical length. To show the validity of the proposed method, a 3rd order 0.5 dB ripple Chebyshev fitter with a center frequency of 900 MHz and a fractional bandwidth(FBW) of 10 % was designed and fabricated. The fabricated filter was based on CER-10 substrate of Taconic Inc. with 1SV277 varactor diode of Toshiba Inc. The center frequency of the fabricated filter can be changed from 606 MHz to 944 MHz, 338 MHz with the control voltage from 0.5 V to 4 V. The insertion loss of the proposed filter is increased with the increment of the control voltage, and the filter characteristics are well reserved expect of slight change of the bandwidth with the various control voltage.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.21 no.6
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• pp.117-125
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• 2007

Recently, a fuel cell with low voltage and high current output characteristics is remarkable for new generation system. It needs both a DC-DC step-up converter and DC-AC inverter to be used in fuel cell generation system. Therefor, this paper, consists of an isolated DC-DC converter to boost the fuel cell voltage 380[VDC] and a PWM inverter with LC filter to convent the DC voltage to single-phase 220[VAC]. Expressly, The fuel cell system which it proposes DC-DC the efficient converter used PWM the phase transient control law and it depended to portion resonance ZVS switching, loss peek voltage and electric current of realization under make schedule, switching frequency anger and the switch reduction. And mind benevolence it sprouted 2 in stop circuit and it added and a direct current voltage and the electric current where the ingredient is reduced in load side ripple stable under make whom it will be able to supply. Besides the efficiency of 92[%]is obtained over the wide output voltage regulation ranges and load variations. Also, under make over together the result leads simulation and test, the propriety confirmation.