• Journal of Electrical Engineering and Technology
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• v.12 no.3
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• pp.1187-1194
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• 2017

In this paper, a high step-up DC-DC PWM converter with continuous input current and low voltage stress is presented for renewable energy application. The proposed converter is composed of a boost converter integrated with an auxiliary step-up circuit. The auxiliary circuit uses an additional coupled inductor and a balancing capacitor with voltage doubler and switching capacitor technique to achieve high step-up voltage gain with an appropriate switch duty cycle. The switched capacitors are charged in parallel and discharged in series by the coupled inductor, stacking on the output capacitor. In the proposed converter, the voltage stress on the main switch is clamped, so a low voltage switch with low ON resistance can be used to reduce the conduction loss which results in the efficiency improvement. A detailed discussion on the operating principle and steady-state analyses are presented in the paper. To justify the theoretical analysis, experimental results of a 200W 40/400V prototype is presented. In addition, the conducted electromagnetic emissions are measured which shows a good EMC performance.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.17 no.3
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• pp.65-70
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• 2008

Capacitive position sensing with modulation technique is widely used in electrostatic actuator applications. To maximize the electrostatic force and the position-sensing gain, capacitors for driving and capacitors for sensing are shared, i.e, after applying the driving voltage with high-frequency modulating signals using op amps, the position is demodulated from the modulated signal. In high-voltage applications, however, low bandwidth of a high-voltage op amp hinders adding the high-frequency modulating signal to the driving voltage. In this paper, new and very simple driving and sensing method is proposed, in which the pulse-width modulated driving voltage eliminates the need of the high-frequency modulating signal for position sensing. This new algorithm is proved by the simulation results using Matlab/SIMULINK.

• Journal of Power Electronics
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• v.19 no.3
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• pp.714-726
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• 2019

This paper proposes a hybrid-boost Modular Multilevel Converter (MMC) for the Medium-Voltage (MV) Variable Speed Drives (VSDs) employed in subsea applications, such as oil and gas recovery. In the presented architecture, a hybrid-boost MMC with a reduced number of semiconductor devices driving a multiphase Induction Machine (IM) is investigated. The stepped output voltage generated by the MMC reduces or eliminates the filtering requirements. Moreover, the boosting capability of the proposed architecture eliminates the need for bulky low-frequency transformers at the converter output terminals. A detailed illustration of the hybrid-boost MMC operation, the expected limitations/constraints, and the voltage balancing technique are presented. A simulation model of the proposed MV hybrid-boost MMC-based five-phase IM drive has been built to investigate the system performance. Finally, a downscaled prototype has been constructed for experimental verification.

• Journal of the Korean Institute of Telematics and Electronics C
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• v.34C no.12
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• pp.28-36
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• 1997

In this paper, system application techniques of a low-voltage low-power CMOS comparator are proposed. The proposed techniques employ poly-layer lines instead of conventional dummy cells to improve the accuracy of comparators which are located in both ends of a comparator array. This technique is easily applicable for hihg-density systems such as memory. The proposed circuits are implemented using a 0.6 um signle-poly double-metal n-well CMOS technology and the dissipated power is 0.38 mW. at a 20MHz clock speed based on a 3V supply. The comparator offsets are measured separately and compared for system applications. Using the proposed techniues, the measured comparator offsets are reduced by 40% of a conventional case.

• Proceedings of the KSR Conference
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• 2000.05a
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• pp.202-209
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• 2000

This paper introduces the main function and protection method of IGBT gate driver that designed by KOROS. Recently, the applications of insulated gate bipolar transistors(IGBTs) have expanded widely, particularly in the area of railway converters. This driver is suitable for railway traction applications, so they are designed for circumstance of railway vehicle such as vibration. The input control power for this driver is supplied from battery charger of railway. it is no necessary an isolated power supply board or auxiliary power supply, with substantial savings in cost and space in railway applications. This gate driver can be used wide range of input voltage. So, performance of the driver has no relation with the battery voltage(70V∼110V). The protection methods of IGBT gate driver have many kind of ways, but this gate driver it designed to apply to converter for railway system, so this gate driver includes protection for arm short current and low control power voltage, etc. And the process of protection method and protection reference value are optimized by means of sufficient test with our own facilities.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.52 no.4
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• pp.183-190
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• 2003

We report the performance of an open-frame type low-voltage high-current DC-DC converter module developed using an active clamp forward converter circuit and current doubler rectifier. The converter module is designed with the specifications of an 1.8V output voltage, 25A output current, and 36-75V input voltage. The synchronous rectifier is used to reduce the conduction fuss at high current level and current-mode control is adapted to enhance the flexibility in the system configuration. A prototype converter module is successfully implemented within 10mm height and half brick size (58${\times}$61mm), and recorded an 84% efficiency and 4% voltage regulation for the entire input voltage range, thereby demonstrating its application potentials to future telecommunication electronics.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.52 no.4
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• pp.183-183
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• 2003

We report the performance of an open-frame type low-voltage high-current DC-DC converter module developed using an active clamp forward converter circuit and current doubler rectifier. The converter module is designed with the specifications of an 1.8V output voltage, 25A output current, and 36-75V input voltage. The synchronous rectifier is used to reduce the conduction fuss at high current level and current-mode control is adapted to enhance the flexibility in the system configuration. A prototype converter module is successfully implemented within 10mm height and half brick size (58×61mm), and recorded an 84% efficiency and 4% voltage regulation for the entire input voltage range, thereby demonstrating its application potentials to future telecommunication electronics.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.12
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• pp.2257-2261
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• 2007

A new CMOS transresistance amplifier for low-voltage analog integrated circuit design applications is presented. The proposed transresistance amplifier circuit based on common-source and negative feedback topology is compared with other recent reported transresistance amplifier. The proposed transresistance amplifier achieves high transresistance gain, gain-bandwidth with the same input/output impedance and the minimum supply voltage $2V_{DSAT}+V_T$. Hspice simulation using 1.8V TSMC $0.18{\mu}m$ CMOS technology was performed and achieved $59dB{\Omega}$ transresistance gain which is above the maximum about $18dB{\Omega}$ compared to transresistance gain of the reported circuit.

• Proceedings of the KIEE Conference
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• 1999.07e
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• pp.2326-2328
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• 1999

Developments of effective and economic diagnostic apparatus for industrial plastic insulated high voltage power cables are in discontented condition still. Some report told that DC high voltage was damaged plastic insulation of a partially aged power cable to lead breakdown easily. But now, we have no alternative tools of DC diagnostic apparatus, and we try to reduce a possibility of hazard DC diagnosis. DC diagnostic apparatus still have many advantages to field cable engineer like low price, portability easy applications and sufficient data. Main hazard of DC diagnosis is excessive hight of applied voltage Recent developments for DC diagnosis use considerably low voltage. But new test methods need special measuring device and manipulator, like high input impedance voltmeter, low leakage current high voltage switches, etc. So that reason, new DC diagnostic devices are normally very expensive and have low efficiency, economically. We try to design a composite test device for 3$\sim$4 newly developed method, have economical benefit th industrial engineer.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.49 no.10
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• pp.693-700
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• 2000

A direct torque control algorithm for 3-level inverter-fed induction motors is presented. Conventional voltage selection methods provoke some problems such as stator flux drooping phenomenon and undersirable torque control appeared especially at the low speed operation. To overcome these problems, a proposed method uses intermediate voltage vectors, which are inherently generated in 3-level inverters. In the proposed algorithm, both subdivision of the basic switching sectors and applications of tntermediated voltages improve the low speed operation characteristics. This algorithm basically considers applications in which direct torque controlled induction motors are fed by 3-level inverters with low switching frequency around 500Hz. An adaptive observer is also employed to bring better responses at the low speed operation, by estimating some state-variables, motor speed and motor parameters which take a deep effect on the performance of the low speed operation. Simulation and experiment results verify effectiveness of the proposed algorithm.