• Electrical & Electronic Materials
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• v.9 no.8
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• pp.813-818
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• 1996

Amorphous As$_{10}$Ge$_{15}$ Te$_{75}$ device shows the memory switching characteristics under d.c. bias. In bulk material, a-As$_{10}$Ge$_{15}$ Te$_{75}$ switching threshold voltage (V$_{th}$) is very high (above 100 volts), but in the case of thin film, V$_{th}$ decreases to a few or ten a few volts. The characteristics of V$_{th}$ depends on the physical dimensions such as the thickness of thin film and the separation between d.c. electrodes, and the annealing conditions. The switching threshold voltage decreases exponentially with increasing annealing temperature and annealing time, but increases linearly with the thickness of thin film and exponentially with increasing the separation between d.c. electrodes. The desirable low switching threshold voltage, therefore, can be obtained by the stabilization through annealing and changing physical dimensions.imensions.sions.

• Proceedings of the KIPE Conference
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• 1997.07a
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• pp.261-265
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• 1997

Driving the electrodeless fluorescent lamp, the high ac voltage with high frequency is required. The linear power amplifier has been widely used as a driving circuit of electrodeless fluorescent lamp. However, the low efficiency of the power amplifier causes th driving circuit to be replaced by a PWM switching inverter. In order to use a PWM switching inverter as the driving circuit of an electrodeless fluorescent lamp, the high switching frequency is required. But due to the switching loss at switches of the inverter, the limitation of high switching frequency appears in the inverter. One solution to this limitation is to reduce the switching loss by using the zero voltage switching technique. In this paper, zero voltage switching resonant inverter for driving an electrodeless fluorescent lamp is discussed. The results of analysis about the inverter are presented and the equations for design are established. And the validity of the analyzed results are verified through the experiment.

• Proceedings of the KIEE Conference
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• 1992.07b
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• pp.1133-1135
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• 1992

This paper describes high frequency inverter using zero voltage switching(ZVS). The ZVS operation is achieved to reduce the switching stress and switching loss under high speed switching. The proposed circuit configuration and performance are discussed. Its operation characteristics are evaluated through computer-aided simulation.

• Proceedings of the Korea Society of Information Technology Applications Conference
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• 2005.11a
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• pp.119-122
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• 2005

A algorithm for control and performance of a pulse-density-modulated (PDM) series-resonant voltage source inverter developed for corona-dischange precesses is presented. The PDM inverter produces either a square-wave ac-voltage state or a zero-voltage state at its ac terminals to control the average output voltage under constant dc voltage and operating frequency. Moreover it can achieve zero-current-switching (ZCS) and zero-voltage-switching (ZVS) in all the operating condition for a reduction of switching lost. Even though the corona discharge load with a strong nonlinear characteristics, new high frequency resonant inverter is shown the wide range power control from 5% to 100%.

• Proceedings of the KIEE Conference
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• 2004.04a
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• pp.136-139
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• 2004

This paper presents a buck circuit topology of high-frequency with a single switching element. It solved the problem which arised from hard-switching in high-frequency using a resonant snubber and operating under the principle of ZCS turn-on and ZVS turn-off commutation schemes. In the existing circuit, it has the voltage stress which is twice of input voltage in free-wheeling diode. But in the proposed circuit, it has voltage stress which is lower than input voltage with modifing a location of free-wheeling diode. In this paper, it explained the circuit operation of each mode and confirmed the waveform of each mode with simulation result. Also the experiment result verified the simulation waveform and compared the existing voltage stress of free-wheeling diode with the proposed voltage stress of that. Moreover, it compares and analyzes the proposed circuit's efficiency with the hard-switching circuit's efficiency according to the change of load current.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.52 no.12
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• pp.713-721
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• 2003

This paper analyzes the switching overvoltage occurred on 345kV underground power cable system as well as combined transmission system using EMTP. Cable length and closing time, preinsertion resistance have effect on switching overvoltage. Therefore, this paper analyzes the switching overvoltage occurred on conductor and sheath with change of those parameters. Specially, the cross bonding position becomes discontinuity point because of the difference between surge impedance of metal sheath and that of lead cable. Thus, the transmission and the reflection of traveling wave complexly occur at this connection point. According to these influences, voltage between sheath and earth as well as voltage between joint boxes rise. Time to crest point of switching overvoltage is longer than lightning overvoltage. Even though the voltage induced by switching surge is smaller than lightning surge, that voltage may have serious effect on the metal sheath. Therefore, this paper also analyses the reduction effect of switching overvoltage when the preinsertion resistance of circuit breaker is considered.

• Journal of Electrical Engineering and Technology
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• v.11 no.6
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• pp.1634-1644
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• 2016

In this paper, a current-fed two-inductor bi-directional DC/DC converter using resonance (CF-TIBCR) and its design method are proposed. The CF-TIBCR has characteristics of low current ripple and a high current rating because of two separated inductors. Also, it achieves zero voltage switching for all switches and zero current switching for switches of a low voltage stage by using the resonant tank. Besides, a voltage spike problem in conventional current-fed converters is solved without the need for an additional snubber or clamping circuits. As a result, the CF-TIBCR features high step-up and high efficiency. Since the proposed converter has difficulty achieving the soft-switching condition when the converter requires the low voltage transfer ratio, a method that varies the number of resonant cycles is adopted to extend the output voltage range with satisfying the soft-switching condition. The principles of the operation characteristics are presented with a theoretical analysis, and the proposed converter is verified through results of an experiment using a laboratory prototype.

• Journal of Power Electronics
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• v.3 no.2
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• pp.90-98
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• 2003

This paper presents a performance analysis in steady-state of a novel type Auxiliary Resonant Commutation Snubber-linked 3-level 3-phase voltage source soft switching inverter suitable and acceptable for high-power applications in comparison with other three types of 3-level 3-phase voltage source soft switching inverters. This soft switching inverter operation which can operate under a condition of Zero Voltage Switching (ZVS). The practical steady -state performances of this inverter are illustrated and evaluated on the basis of the experimental results.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1998.06a
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• pp.527-533
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• 1998

An optimized PWM switching strategy for an induction motor voltage control is developed and demonstrated. Space vector modulation in voltage source inverter offers improved DC-bus utilization and reduced commutation losses, and has been therefor recognizedas the perfered PWM method, especially in the case of digital implementation. Three-phase invertor voltage control by space vector modulation consists of switching between the two active and one zero voltage vector by using the proposed optimal PWM algorithm. The prefered switching sequence is defined as a function of the modulation index and period of a carrier wave. The sequence is selected by suing the inverter switching losses and the current ripple as the criteria. For low and medium power application, the experimental results indicate that good dynamic response and reduced harmonic distortion can be achieved by increasing switching frequency.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.54 no.5
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• pp.231-237
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• 2005

Many conventional multi-level inverters have detected switching faults by using the over voltage and current. However, fault detection of the switching elements is very difficult because the voltage and current due to each switching fault decrease more than the normal operation. Moreover, the dc-link unbalancing voltage causes a serious problem in the safety and reliability of system when the 3-level inverter faults occur Therefore, this paper proposes the simple fault diagnose method and the neutral-point-voltage control method that can protect the 3-level inverter system from the unbalancing voltage of the do-link capacitors when the faults of switching elements occur in the 3-level inverter that is very efficient in ac motor drives of the high voltage and high power applications. Through experiment results, the validity of the proposed method is demonstrated.