• Progress in Superconductivity and Cryogenics
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• v.20 no.4
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• pp.55-59
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• 2018

Currently, the development of industry makes needs larger electric supply. Providers must consider the efficiency about losses and reliability of the system. In this case, DC power system can save electrical energy; long-distance transmission line losses. Relevance to switch technology with a voltage-source converter (VSC) in AC-DC conversion system have been researched. But, protection device of DC-link against fault current is still needed to study much. VSC DC power system is vulnerable to DC-cable short-circuit and ground faults, because DC-link has a huge size of capacitor filter which releases extremely large current during DC faults. Furthermore, DC has a fatal flaw that current zero crossing is nonexistence. To interrupt the DC, several methods which make a zero crossing is used; parallel connecting self-excited series LC circuit with main switch, LC circuit with power electronic device called hybrid DC circuit breaker. Meanwhile, self-excited oscillator needs a huge size capacitor that produces big oscillation current which makes zero crossing. This capacitor has a quite effective on the price of DCCB. In this paper, hybrid self-excited type superconducting DCCB which are using AC circuit breaker system is studied by simulation tool PSCAD/EMTDC.

• ETRI Journal
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• v.27 no.5
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• pp.539-544
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• 2005

An analog CMOS vision chip for edge detection with power consumption below 20mW was designed by adopting electronic switches. An electronic switch separates the edge detection circuit into two parts; one is a logarithmic compression photocircuit, the other is a signal processing circuit for edge detection. The electronic switch controls the connection between the two circuits. When the electronic switch is OFF, it can intercept the current flow through the signal processing circuit and restrict the magnitude of the current flow below several hundred nA. The estimated power consumption of the chip, with $128{\times}128$ pixels, was below 20mW. The vision chip was designed using $0.25{\mu}m$ 1-poly 5-metal standard full custom CMOS process technology.

• The Transactions of the Korean Institute of Power Electronics
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• v.7 no.2
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• pp.129-136
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• 2002

A single-phase inverter using a diode bridge-type resonant circuit to implement ZVT(Zero Voltage Transition) switching is presented. It Is shown that the ZACE(Zero Average Current Error) algorithm based Polarized ramptime current control can provide a suitable interface between DC link of diode bridge-type resonant circuit and the inverter. The current control algorithm is analyzed about how to design the circuit with auxiliary switch which can ZVT operation for the main power switch. The simulation and experimental results would be shown to verify the proposed current algorithm, because the main Power switch is turn on with ZVT and the hi-directional inverter is operated.

• Proceedings of the KIPE Conference
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• 2001.10a
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• pp.247-250
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• 2001

This paper presents a simple and cost effective circuit topology of single-ended type high frequency quasi-resonant PWM inverter using IGBTs, which can operate under wide soft switching operation range based on ZCS for main power switch as compared with a conventional active voltage-clamped ZVS-PWM high frequency quasi-resonant inverter developed previously. In principle, this new circuit topology can efficiently operate under a constant frequency PWM control-based power regulation scheme. In particular, it is noted that the zero current soft switching (ZCS) commutation can achieve for the main active power switch. On the other hand, the zero voltage soft switching (ZVS) commutation can also achieve for the auxiliary active power switch. The operating principle of this high-frequency Inverter treated here and its power regulation characteristics are illustrated on the basis of the simulation and feasible experimental results.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.2100-2101
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• 2008

This paper is studied on a protective control system for electrical fire and electrical faults due to over current or electric short circuit faults by using electrical thermal characteristics of PTC (Positive Temperature Coefficient) thermistor and current response characteristics of high sensitive reed switch. The PTC thermistor has characteristic of positive resistivity temperature coefficient according to the temperature variation, which is construction of a regular square and cube demarcation with BaTiO3_Ceramics of positive temperature coefficient. Also PTC thermistor shows the phenomenon which is rapidly increased in the resistivity if the temperature is increased over Curie temperature point, and reed switch, which is used for electrical fault current sensing devices, have a excellent characteristic of response velocity in degree of ${\mu}s{\sim}ms$ that sensing magnetic flux in proportion to dimension of line current. This paper is proposed on a protective control system use PTC thermistor and reed switch for sensor which is protected from electrical fire due to overload faults or electric short circuit faults. Some experimental results of the proposed electric safety control device are confirmed to the validity of the analytical results.

• ETRI Journal
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• v.36 no.6
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• pp.881-888
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• 2014

This paper studies the magnetic coupling between two adjacent loop antennas that are parallel to each other in a plane and presents a new practical method to avoid the resulting magnetic coupling interference. The study focuses on the high frequency radio-frequency identification (RFID) system for casino applications, where several loop antennas are closely built into a game table to monitor gaming chips. In this case, neighboring loop antennas may severely interfere with each other by magnetic coupling, which leads to the malfunction of the RFID system. In this paper, we present a practical loop antenna with a new loop switch circuit for avoiding magnetic coupling. The loop switch circuit is integrated with a matching circuit and automatically operated by using an interrogating signal from a reader. We verified the validity of the proposed design by showing that an RFID reader with the proposed antenna can exactly and separately read the gaming chips placed on the different betting zones of a game table.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.8 no.5
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• pp.1076-1081
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• 2007

In this paper, we propose a new switch structure for time division duplex(TDD) system. The existing TDD structure utilizes a circulator fur isolation characteristic between ports. However, the circulator produces intermodulation distortion signals which are undesired signal because of its nonlinear properties. The proposed circuit is composed of a modified branch-line hybrid coupler which controls the signal flow while the isolated port is open-/short- terminated. In order to prove the validity of the presented structure, the switch circuit is fabricated and measured at 2.3GHz, the center frequency of Wibro service system.

• Journal of the Semiconductor & Display Technology
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• v.19 no.4
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• pp.99-104
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• 2020

In this paper, efficiency and loss characteristics of GaN FET were reported by applying it into the QR flyback converter. In particular, for the comparison of efficiency characteristics, QR flyback converter experimental circuits with Si FET and with GaN FET were separately produced in 12W class. As a result of the experiment, the experimental circuit of the QR flyback converter using GaN FET reached a high efficiency of 90% or more when the load power was 2W or more, and the maximum efficiency was observed to be about 92%, and the maximum loss power was about 1.1W. Meanwhile, the efficiency of the experimental circuit with Si FET increased as the input voltage increased, and the maximum efficiency was observed to be about 82% when the load power was 9W or higher, and the maximum loss power was about 2.8W. From the results, it is estimated that that in the case of the experimental circuit applying the GaN FET switch, the power conversion efficiency was improved as the switching loss and conduction loss due to on-resistance were reduced, and the internal loss due to the synchronous rectifier was minimized. Consequently, it is concluded that the GaN FET is suitable for under 20W class power supply unit as a high efficiency power switch.

• Journal of the Korean Institute of Telematics and Electronics C
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• v.36C no.5
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• pp.1-12
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• 1999

A new algorithm of constructing binary decision diagram(BDD) for design verification of switch-level circuits is proposed in this paper. In the switch-level circuit, functions are characterized by serial and parallel connections of switches and the final logic values may have high-impedance and unstable states in addition to the logic values of 0 and 1. We extend the BDD to represent functions of switch-level circuits as acyclic graphs so called switch-level binary decision diagram (SLBDD). The function representation of the graph is in the worst case, exponential to the number of inputs. Thus, the ordering of decision variables plays a major role in graph sizes. Under the existence of pass-transistors and domino-logic of precharging circuitry, we also propose an input ordering algorithm for the efficiency in graph sizes. We conducted several experiments on various benchmark circuits and the results show that our algorithm is efficient enough to apply to functional simulation, power estimation, and fault-simulation of switch-level design.

• Proceedings of the KIEE Conference
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• 2003.07a
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• pp.455-457
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• 2003

In the present IEC 60427(2000), reduced applied voltage can be used for synthetic short-circuit making current tests if the maximum pre-arcing time of the test circuit breaker is less than $1/{\omega}$. But in the near future IEC, only the making tests with full test voltage shall be allowed. To meet this trend, KERI is preparing synthetic making test facilities using step-up transformer, ITMC and plasma making switch. This paper presents analytical characteristics of KERI's synthetic short-circuit making test circuits. The results of this paper can be useful for effective and adequate tests.