• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.8
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• pp.1580-1584
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• 2009

We have theoretically analyzed the monolithic integration of vertical cavity lasers with depleted optical thyristor (VCL-DOT) structure and experimentally demonstrated optical logic gates such as AND-gate, OR-gate, and INVERTER implemented by VCL-DOT for an optical programmable gate array. The optical AND and OR gates have been realized by changing a input bias of the single VCL-DOTs and all kinds of optical logic functions are also implemented by adjusting an intensity of the reference input beams into the differential VCL-DOTs. To achieve the high sensitivity, high slope efficiency and low threshold current, a small active region of lasing part and a wide detecting area are simultaneously designed by using a selective oxidation process. The fabricated devices clearly show nonlinear s-shaped current-voltage characteristics and lasing characteristics of a low threshold current with 0.65 mA and output spectrum at 854 nm.

• Journal of electromagnetic engineering and science
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• v.1 no.2
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• pp.131-138
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• 2001

The DTV (Digital TV) tuner for an 8-VSB (Vestigial Side-Band) modulation was developed to meet the requirements of the ATSC (Advanced Television Systems Committee). The double frequency conversion and the active tracking filter in the front-end were used to cancel interferences between adjacent channels and multi-channels by suppressing the IF beat and the Image frequency. However, It was impossible to get frequency mapping between the tracking filter and the first VCO (Voltage Controlled Oscillator) in the existing DTV tuner structure which differs from the NTSC (National Television Systems Committee) tuner. This paper, therefore, suggests an assailable structure and a new method for the automatic frequency selection by mapping the frequency characteristics over the tracking voltage and the combined HW which is composed of a Micro-controller, an EEPROM (Electrically Erasable Programmable Read Only Memory), a DAC (Digital-to-Analog Converter), an OP amplifier, and a switch driver.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.61 no.3
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• pp.355-360
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• 2012

It is difficult to converge power flow for the power system planning data. The main cause of power flow diverse is reactive power imbalance. A active power could be adjust by ELD or merit order but a reactive power couldn't dispatch before power flow analysis. The lack of reactive power of power system is cause a inadequate voltage drop This paper suggest new reactive power dispatch algorithm using switched shunt admittance. This algorithm uses reactive power sensitivity called switch shunt jacobian. When proposed algorithm applies to real system data that couldn't be conversed in PSS/E the power flow analysis is converged.

• Proceedings of the KIPE Conference
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• 1998.10a
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• pp.374-379
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• 1998

This paper proposes a control method for three-phase PWM rectifier using only single current sensor in DC link. A PWM modulation strategy for reconstructing three phase current from the DC link current is given. The states of the rectifier switch are modified so that all phase currents can be reconstructed in a switching period although one of active vectors is applied only for a short time. Therefore, a novel current control using an adjustment scheme of the modulation signal for a three-phase PWM rectifier will be discussed, and verified with the experimental results.

• The Transactions of the Korean Institute of Power Electronics
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• v.3 no.4
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• pp.426-436
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• 1998

Identification of fault current during the operation of a power semiconductor switch and activation of suitable remedial actions are important for reliable operation of power converters. A short circuit is a basic and severe fault situation in a circuit structure such as voltage source converters. This paper presents a new active protection circuit for fast and precise clamping and safe shutdown of fault currents of the IGBTs. This circuit allows operation of the IGBTs with a higher on-state gate voltage, which can thereby reduce the conduction loss in the device without compromising the short circuit protection characteristics. The operation of the circuit is studied under various conditions, considering variation of temperature, rising rate of fault current, gate voltage value, and protection circuit parameters. An evaluation of the operation of the circuit is made using IGBTs from different to confirm the effectiveness of the protection circuit.

• Proceedings of the KIPE Conference
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• 1998.10a
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• pp.620-624
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• 1998

Higher operating frequency provides rising output power from modern power electronics devices. Nevertheless, the switch-mode operation results in EMI which is produced due to large di/dt and/or dv/dt. The methods to reduce EMI are the use of classic and expensive input filters or the addition of the active filter into the main circuits. In this paper, by using the randomized PWM the EMI effect can be reduced and implementation of the proposed control scheme into the forward converter can improve the harmonic spectrum as well

• Proceedings of the KIEE Conference
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• 1999.11b
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• pp.406-408
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• 1999

In order to reduce the overall size and cost, researchers attempted to integrate the functions of power factor correction(PFC) and isolated dc-dc conversion into single power stage. However, single-stage isolated PFC converters have higher voltage stress and heavier loss when compared with a normal dc-dc converters. In this paper, we propose to add active clamping circuit to keep the switch voltage stress low and to achieve soft switching of electronic devices.

• Journal of Power Electronics
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• v.6 no.1
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• pp.1-7
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• 2006

This paper is a record of the study on a high efficiency and high power chopper based on the new soft switching method QRAS (Quasi~resonant Regenerating Active Snubber) designed for a Fuel Cell Electric Vehicle (FCEV). This power chopper is basically proposed for 25kHz soft switching. To confirm the practicality and effectiveness of the converter, the fabrication of a prototype-model using IGBTs was completed. Additionally, a 8kW rating test, a light load test, a current discontinuous mode test and a stable operation resonance test was completed. The circuit geometry, the basic operation, and the 8kW one-tenth-prototype test results are reported with a $97.5\%$ efficiency measurement.

• Proceedings of the KIEE Conference
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• 2000.07b
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• pp.1065-1067
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• 2000

This paper describes performance analysis of ARCP Inverter, which can offer zero voltage switching at nominal voltage stress. The system consists of a voltage-source inverter with sort-switching module. Each main switch is connected in parallel with resonant capacitor and two auxiliary switches are placed in series with a resonant reactor for soft-switching capability. The described ARCP inverter could be effectively applied for active power filter reactive power compensator, and UPS.

• JSTS:Journal of Semiconductor Technology and Science
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• v.15 no.3
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• pp.319-325
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• 2015

This paper presents an efficient vibration energy harvester with a piezoelectric (PE) cantilever. The proposed PE energy harvester increases the efficiency through minimization of hardware complexity and hence reduction of power dissipation of the circuit. Two key features of the proposed energy harvester are (i) incorporation synchronized switches with a simple control circuit, and (ii) a feed-forward buck converter with a simple control circuit. The chip was fabricated in $0.18{\mu}m$ CMOS processing technology, and the measured results indicate that the proposed rectifier achieves the efficiency of 77%. The core area of the chip is 0.2 mm2.