• Journal of the Korean Ceramic Society
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• v.39 no.2
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• pp.120-125
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• 2002

AC powder EL devices were fabricated by screen printing method with the dielectric materials in insulating layer and the electrical resistivity of rear electrode. Brightness and current density were measured at voltage range of 50∼300 $V_{rms}$ to estimate optoelectrical properties of AC powder EL devices, respectively. Frequency generator was used as system producing frequency and voltage of a sine wave. Brightness and current density were measured by luminometer and multimeter. Also, dielectric constant for dielectric layer was measured by impedance analyser after preparing thick film. Dielectric constant was improved with amount of $TiO_2$ to $BaTiO_3$ powder. By applying such a process to dielectric layer of low cost AC powder EL device, brightness was improved to 50 cd/$m^2$ at similar current density. Dielectric constant $BaTiO_3$ powder by solution combustion process is better than commercial $BaTiO_3$ powder. By applying to that of low power consumption AC powder EL device, brightness was improved to 85 cd/$m^2$. Brightness of AC powder EL device was relatively decreased by control of electrical resistivity of rear electrode, current density was also decreased.

• Journal of the Korean Ceramic Society
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• v.38 no.12
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• pp.1085-1092
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• 2001

The high efficient AC powder EL devices classified by low cost and low power consumption type fabricated using screen printing method with film thickness and organic binder. Brightness and current density were measured at frequency range of 400Hz∼1kHz and voltage range of 50∼300V$\_$rms/ to estimate optoelectrical properties of AC powder EL devices, respectively. Frequency generator was used as system producing frequency and voltage of a sine wave. Also brightness and current density were measured by luminometer and multimeter. In the case of low cost type AC powder EL device, brightness and current density were about 43 cd/m$^2$and 20$\mu$A/cm$^2$when the thickness of phosphor and dielectric layer was 45∼50$\mu$m under no addition of plasticizer respectively. In the case of low power consumption type AC powder EL device, brightness and current density were about 74 cd/m$^2$and 30∼40$\mu$A/cm$^2$when the thickness of phosphor and dielectric layer was 45∼50$\mu$m and 15∼20$\mu$m under addition of 15wt% plasticizer respectively. Also, AC powder EL device fabricated in this study showed absolutely excellent characteristics as the lifetime was longer than products of other company.

• Journal of the Microelectronics and Packaging Society
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• v.15 no.3
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• pp.19-25
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• 2008

In this paper, author proposes a novel step-up AC-DC chopper operated with power factor correction(PFC) and with high efficiency. The proposed chopper behaves with discontinuous current control(DCC) of input current. The input current waveform in the proposed chopper is got to be a discontinuous sinusoid form in proportion to magnitude of ac input voltage under the constant duty cycle switching. Therefore, the input power factor is nearly unity and the control method is simple. In the general DCC chopper, the switching devices are turned-on with the zero current switching, but turn-off of the switching devices is switched at current maximum value. To achieve a soft switching of the switching rum-off, the proposed chopper is used a new partial resonant circuit. The result is that the switching loss is very low and the efficiency of chopper is high.

• Progress in Superconductivity and Cryogenics
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• v.14 no.3
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• pp.9-12
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• 2012

Usually, the AC loss from the superconducting element of an SFCL due to the load current is very small because it is composed of the combination of bifilar windings with very small reactance. Although the AC loss is small enough, we should be albe to predict for the design and control of the cryogenic system. In fact, an SFCL for the transmission voltage class may not generate ignorable AC loss because of the inevitable space between the HTS wires for the high voltage insulation and cryogenic efficiency. To measure the AC loss dependency on the space between the 2G HTS wires with the width of 4.4 mm, we prepared an experimental setup which could adjust the distance between the wires. We used two 500-mm length HTS wires in parallel and applied the current in the opposite direction for each wire to simulate a part of a current limiting module for a high voltage SFCL. We also put two couples of voltage taps at the ends of each wire and a cancel coil in the voltage measurement circuit to compensate the reactive component from the voltage taps. In this condition, we varied the distance between the wires to investigate the change of the transport current loss. A similar experimental study with HTS wire with the width of 12 mm is now in progress.

• Proceedings of the KIPE Conference
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• 2004.07b
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• pp.597-600
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• 2004

In this paper, a static var compensator using PWM Cuk AC-AC converter is presented. The PWM Cuk AC-AC converter is modelled by using complex circuit DQ transformation whereby the basic condition to be used as a var compensator is derived and the static characteristic equations such as input current and reactive power is analytically obtained. Finally, the PSIM simulations show the validity of the modelling and analysis.

• Proceedings of the KIPE Conference
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• 2014.07a
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• pp.13-14
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• 2014

This paper is proposed the PFC control method of boost converter using a charging current of the capacitor. Around AC voltage peak point, PFC operation is stopped and the charging current of the capacitor is flowed. The charging current of the capacitor and the switching current makes the AC input current. The 150[W] converter was confirmed high PF and low THD.

• Transactions on Electrical and Electronic Materials
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• v.14 no.4
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• pp.177-181
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• 2013

In this paper, silicon solar cells are analyzed regarding power conversion efficiency by changed capacitance in the depletion region. For the capacitance control in the depletion region of silicon solar cell was applied for 10, 20, 40, 80, 160 and 320 Hz frequency band character and alternating current(AC) voltage with square wave of 0.2~1.4 V. Academically, symmetry formation of positive and negative change of the p-n junction is similar to the physical effect of capacitance. According to the experiment result, because input of square wave with alternating current(AC) voltage could be observed to changed capacitance effect by indirectly method through non-linear power conversion (Voltage-Current) output. In addition, when input alternating current(AC) voltage in the silicon solar cell, changed capacitance of depletion region with the forward bias condition and reverse bias condition gave a direct effect to the charge mobility.

• Proceedings of the KIPE Conference
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• 1998.10a
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• pp.928-933
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• 1998

This paper presents a novel current control system to eliminate the steady state control error and to improve the transient characteristics for PWM AC-DC converter. A general mathematical model of the converter that is represented as a state-space model is first established. The state-space model is used for the simulation of PWM switching converter with the proposed current control system. The proposed sinusoidal tracking control system that does not require coordinate transformations using principle of the integral controller is described. It is proved that the steady state deviation reduces to zero through a transfer function of source current control system. Finally, it is seen that simulations agree with the experimental results in source current and reference of controlled ac current loop.

• Proceedings of the KIEE Conference
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• 1998.07f
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• pp.1944-1946
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• 1998

This paper presents a novel current control system to eliminate the steady state control error for PWM AC-DC converter. A general mathematical model of the converter which is represented as a state-space model is established. The state-space model is used for the simulation of converter with the proposed tracking control system of sinusoidal current. In this system, a novel current control which do not require coordinate transformations using internal principle of PI controller is described. It is proved that the steady state deviation reduce to zero through a transfer function of source current control system. Finally, simulations show good source current control characteristics by means of a simplified control system which do not require coordinate transformations.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.48 no.9
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• pp.517-522
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• 1999

This paper addresses the issue of current sampling in a high performance AC drive system fed by a discontinuous PWM inverter. The effect of the sampling error due to the measurement delay produced by an input stage low pass filter and an A/D converter is described in the case of discontinuous PWM. To compensate for the sampling error, a method to estimate the delay time of the whole measurement system based on the measured current is proposed and its effectiveness is verified by experimental results. The proposed algorithm can automatically estimate the system delay introduced by the low pass filter and the A/D converter at the commissioning stage. By delaying the current sampling by the estimated value, experimental results indicate that more than 50% reduction of current ripple can be achieved.