• Journal of the Optical Society of Korea
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• v.11 no.1
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• pp.40-43
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• 2007

We propose a taper-underlaid spot-size converter (TU-SSC) with an offset which consists of two vertically stacked taper layers. The designed TU-SSC reduces coupling loss of a high index-contrast waveguide with $1.5%{\Delta}$ to a single mode fiber from 1.5 dB to 0.27 dB. We also considered the effects of mask misalignment in the fabrication process of TU-SSC, and optimized the design of TU-SSC so that the additional loss of TU-SSC for the mask misalignment of $3{\mu}m$ in the photo-lithography process was as low as 0.13 dB.

• The Transactions of the Korean Institute of Power Electronics
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• v.19 no.5
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• pp.391-398
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• 2014

This paper presents a resonant step-down DC/DC converter to reduce the voltage stresses of a 3-phase inverter module under the three-phase AC utility line condition. Under this condition, a conventional 3-phase inverter module suffers from high voltage stresses as a result of the high rectified DC link voltage; hence, a high-cost high-voltage-rating inverter module must be used. However, using the proposed converter, a low-cost low-voltage-rating inverter module may be adopted to drive the motor even under the 3-phase AC line condition. The proposed converter, which can be realized with small size inductor and low-voltage-rating semiconductor devices, operates at a high-efficiency mode because of the zero-current switching operations of all the semiconductor devices. The operational principles are explained and a design example is provided in the study. Experimental results demonstrate the validity of the proposed converter.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.7A
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• pp.568-573
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• 2009

This paper presents a step-down DC-DC converter with On-chip Compensation for battery-operated portable electronic devices which are designed in O.13um CMOS standard process. In an effort to decrease system volume, this paper proposes the on chip compensation circuit using capacitor multiplier method. Capacitor multiplier method can minimize error amplifier's compensation capacitor size by 10%. It allows the compensation block of DC-DC converter be easily integrated on a chip and occupy less layout area. But capacitor multiplier operation reduces DC-DC converter efficiency. As a result, this converter shows maximum efficiency over 87.2% for the output voltage of 1.2V (input voltage : 3.3V), maximum load current 500mA, and 25mA output ripple current. This voltage mode controled buck converter has 1MHz switching frequency.

• The Transactions of the Korean Institute of Power Electronics
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• v.15 no.4
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• pp.259-265
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• 2010

The proposed method offers an improved control method for high power density AC/DC adapter by using more energy efficient electrical equipments. Power factor corrector (PFC) topology is based on boost topology with boundary conduction mode (BCM) and DC/DC topology is based on LLC resonant converter, which helps to reduce size of the semiconductor and the magnetic devices. Test results with 85W AC/DC adapter (18.5V/4.6A) design shows that the measured efficiency is 90% at $90V_{rms}$ input voltage with power density of $36W/in^3$. It also shows low no load power consumption of about 0.5W.

• Transactions on Electrical and Electronic Materials
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• v.14 no.5
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• pp.235-241
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• 2013

A low power CMOS control circuit is applied in an integrated DC-DC buck converter. The integrated converter is composed of a feedback control circuit and power block with 0.35 ${\mu}m$ CMOS process. A current-sensing circuit is integrated with the sense-FET method in the control circuit. In the current-sensing circuit, a current-mirror is used for a voltage follower in order to reduce power consumption with a smaller chip-size. The N-channel MOS acts as a switching device in the current-sensing circuit where the sensing FET is in parallel with the power MOSFET. The amplifier and comparator are designed to obtain a high gain and a fast transient time. The converter offers well-controlled output and accurately sensed inductor current. Simulation work shows that the current-sensing circuit is operated with an accuracy of higher than 90% and the transient time of the error amplifier is controlled within $75{\mu}sec$. The sensing current is in the range of a few hundred ${\mu}A$ at a frequency of 0.6~2 MHz and an input voltage of 3~5 V. The output voltage is obtained as expected with the ripple ratio within 1%.

• The Transactions of the Korean Institute of Power Electronics
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• v.14 no.3
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• pp.211-219
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• 2009

In this paper, a detailed analysis of zero current or zero voltage switching boost converter using a single switch is described. The proposed topology is capable of decreasing switching loss of IGBT device using soft switching technique. As a results, it can be reduced size and weight of passive elements. Based on the mode analysis, practical design considerations are presented. We confirm the converter topology, principle of operation and simulation results obtained from the PSIM software. The performance of the proposed converter is verified by with 1kW(400V, 2.5A) prototype circuit operated at 30kHz.

• Journal of IKEEE
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• v.20 no.3
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• pp.314-317
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• 2016

Recently, efforts to maximize battery life in progress with an increase in the demand for portable devices. In this paper, we propose multi-phase buck converter with fast transient response. Multi-phase buck converter may be used for the output capacitor of small size because the ripple cancellation effect, it is possible to use an inductor having an inductance less. The portable device for quick change from standby mode to active 4-phase design structure was given a fast transient response. The proposed multi-phase buck converter was fabricated using a 0.18 um CMOS process and the supply voltage ranges from 2.7V to 3.3V, the maximum load current is 500mA and settling time is 10us.

• Proceedings of the KIEE Conference
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• 2003.07b
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• pp.1148-1150
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• 2003

Power conversion system must be increased switching frequency in order to achieve a small size, a light weight and a low noise. However, the switches of converter are subjected to high switching power losses and switching stresses. As a result of those, the power system brings on a low efficiency. To improved these, a large number of soft switching topologies included a resonant circuit has been prosed. But these circuits increase number of switch in circuit and complicate sequence of switching operation. In this paper, the authors propose a high power factor and high efficiency DC-DC converter using single-pulse soft switching by partial resonant switching node. The switching devices in a prosed circuit are operated with soft switching by the partial resonant method, that is, Partial Resonant Switch Mode Power Converter. The partial resonant circuit makes use of a inductor using step up and a condenser of loss-less snubber. The result is that the switching loss is very low and the efficiency of system is high. Also the proposed converter is deemed the most suitable for high power applications where the power switching devices are used. Some simulative results on computer results are included to confirm the validity of the analytical results.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.46 no.8
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• pp.31-40
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• 2009

This paper presents a design of a high performance DC-DC boost converter as a power module for SOC designs. It applied to this chip that reduced inductor and capacitor for integrating on a chip, and it operates with a switching frequency of 100MHz. It has reliability and stability in high switching frequency. The controller of DC-DC boost converter is designed by voltage-mode control method and compensated properly. The designed DC-DC converter is fabricated with the 0.18${\mu}m$ standard CMOS technology with a thick-gate oxide option. The overall die size is 8.14$mm^2$, and controller size is 1.15$mm^2$. The converter has the maximum efficiency over 76% for the output voltage of 4V and load current larger 300mA. The load regulation is 0.012% (0.5mV) for the load current change of 100mA.

• Proceedings of the KIEE Conference
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• 1998.11a
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• pp.125-127
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• 1998

The widely used power supply (Switched Mode Power Supply : SMPS) as a source in order to stabilize direct current for electronics or communication systems has merits, when it is compared to the existing source for stability, such as high efficiency, small size, light weight by means of switching process of the semiconductor device which controls the flow of power. However, due to existence of inductors and capacitors used for charging energy, the source part in electronic or communication systems hasn't reached the speed, that is supposed to get, for achieving smaller size and lighter weight. In order to got smallness in size, it is necessary to increase switching frequency. And that makes devices for measuring energy smaller. Nevertheless, the rise switching frequency brings increases in switching loss, inductor loss, and power loss. Also, the occurrence of surge and noise caused by high frequency switching is setting higher. The resonant converter has been considered as one of methods that give solutions for the problems of SMPS and that method has been paid attention as a source technology in electronics and communication.