• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.11a
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• pp.19-22
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• 2003

In this paper, a new small size Lateral Trench Electrode Power MOSFET with local doping is proposed. This new structure is based on the conventional lateral power MOSFET. The entire electrodes of proposed device are placed in trench oxide. The forward blocking voltage of the proposed device is improved by 3.3 times with that of the conventional lateral power MOSFET. The forward blocking voltage of proposed device is about 500V. At the same size, a increase of the forward blocking voltage of about 3.3 times relative to the conventional lateral power MOSFET is observed by using TMA-MEDICI which is used for analyzing device characteristics. Because the electrodes of the proposed device are formed in trench oxide respectively, the electric field in the device are crowded to trench oxide. And because of the structure which has a narrow drain doping width, the punch through breakdown can be occurred in higher voltage than that of conventional lateral power MOSFET. We observed that the characteristics of the proposed device was improved by using TMA-MEDICI and that the fabrication of the proposed device is possible by using TMA-TSUPREM4.

• Proceedings of the KIPE Conference
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• 2001.12a
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• pp.97-101
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• 2001

Recently, as the development of industry, the nonlinear load becomes increased. Because of nonlinear load, the variation of source voltage is generated by the impedace of source side flowed harmonic currents. For blocking harmonic currents by nonlinear load, a series active power filter operates blocking resistance of harmonic currents. The value of blocking resistance shows ideal compensating characteristic out of theoretically infinite value. But the blocking resistance is limited by the problem of the system stability and the capacity of inverter. In this paper, the value of optimum blocking resistance is found by a simulation in the applied system. In the case of unbalanced source voltages, each relation of the blocking resistance is shown. It is proved that blocking resistance of series active power filter relates to a passive filter.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.15 no.9
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• pp.750-757
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• 2002

A new lateral trench LTEIGBT with p+ diverter was proposed to suppress latch-up of LTIGBT The p+ diverter was placed between the anode and cathode electrode. The latch-up of LTEICBT with a p+ diverter was effectively suppressed to sustain an anode voltage of 8.7V and a current density of 1453A/$\textrm{cm}^2$ while in the conventional LTIGBT, latch-up occured at an anode current density of 540A/$\textrm{cm}^2$. In addition, the forward blocking voltage of the proposed LTEIGBT with a p+ diverter was about 140V. The forward blocking voltage of the conventional LTIGBT of the same size was no more than 105V, We fabricated the proposed LTEIGBT with a p+ diverter after the device and process simulation was finished. When the gate voltage is applied 12V, the forward conduction currents of the proposed LTEIGBT with a p+ diverter and the conventional LIGBT are 90㎃ and 70㎃, respectively, at the same breakdown voltage of 150V.

• Proceedings of the KIPE Conference
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• 1996.06a
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• pp.71-75
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• 1996

As the Three-level ZVS PWM DC-DC converter operates likewise full-bridge ZVS PWM DC-DC converter and the blocking voltage of each switching device is a half of the DC-link voltage, it is suitable for the high imput voltage applications. However, it has some problems as follows; The blocking voltage of each devices is unbalanced and it causes the power losses of the inner switching devices to be increased. Also, it has narrow load range so that the switching losses and the efficiency are reduced as it goes to the light load. This paper presents an nove Three-level ZVS PWM DC-DC converter, which can reduce the overvoltage of the outer switches, eliminate the unbalance of the voltage sharing between the switches at turn-off due to the stray inductances, and operate from no load to full load. The characteristics and the performances of the proposed Three-level ZVS PWM DC-DC converter are verified by simulation and experimental results

• The Transactions of the Korean Institute of Power Electronics
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• v.25 no.4
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• pp.261-268
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• 2020

Transformer saturation in full bridge (FB) isolated DC-DC converters is caused by uneven switching speeds and voltage drops in semiconductor devices and mismatched gate signals. In order to prevent transformer saturation, most popular and widely used approach is to insert a capacitor in series with the transformer windings. This study conducts extensive analyses on transformer saturation and the effect of DC blocking capacitors when they are placed in the primary or secondary windings of a transformer. The effect of the DC blocking capacitors is verified in voltage-fed and current-fed FB converters.

• Transactions of the Korean hydrogen and new energy society
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• v.20 no.3
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• pp.224-231
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• 2009

The improvement of cold start capability is one of the most challenging tasks to be solved for commercialization of fuel cell vehicle. In this study, cold start test and ice blocking test(IBT) of fuel cell stack were carried out under various operating conditions. This fuel cell stack can be thawed from -20$^{\circ}$C within 25s and the voltage change was found to be comprised of 4 steps; the first step is the voltage decrease by overpotential, the second step is the voltage increase by the cell temperature increase, the third step is the voltage decrease by ice blocking, and the last step is the voltage increase by thawing. Bootstrap startup was failed after shutdown at temperature under 40$^{\circ}$C because of much condensed water in the fuel cell. Quantitative estimation of cold start capability have been demonstrated by ice blocking test(IBT). In the results, it was found that cold start capability was improved double every 10$^{\circ}$C from 30$^{\circ}$C to 65$^{\circ}$C and enhanced by 30% at the condition of SR 3/4 compared to SR 1.5/2.0 and enhanced by 20% with dry purge condition compared to with RH 50% purge condition.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07a
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• pp.312-315
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• 2003

Basic design of RC-GCTs (Reserve-Conducting Gate-Commutated Thyristors) by novel punch-through (PT) concept with 5,500v rated voltage is described here. A PT and NPT (non punch-through) concept for the same blocking voltage has been compared in detail. The simulation work indicates that GCT with such PT design exhibits that the forward breakdown voltage is 6,400V which is enough for supporting 5500V blocking. Additionally, the real IGCT turn-off in the mode of PNP transistor has been realized. However, the carrier extraction from N-base to gate terminal will be drastic slowly in terms of NPT structure except for the high on-state voltage drop.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.48 no.1
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• pp.51-56
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• 1999

This paper presents a new transient overvoltage blocking device (TOBD) for info-communication facilities with low power and high frequency bandwidth. Conventional protection devices have some problems such as low frequency bandwidth, low energy capacity and high remnant voltage. In order to improve these limitations, thehybrid type TOBD, which consists of a gas tube, avalanche diodes and junction typefield effect transistors (JFETs), was designed and fabricated. The TOBD differs from the conventional protection devices in configuration, and JFETs were used as an active non-linear element and a high speed switching diode with low capacitance limits high current. Therefore the avalanche dilde with low energy capacity are protected fromthe high current, and the TOBD has a very small input capacitance. From the performance test using combination surge generator, which can produce $1.2/50\mus\;4.2kV_{max}\; 8/20\mus\; 2.1kA_{max}$, it is confirmed that proposed TOBD has an excellent protection performance in tight clamping voltage and limiting current characteristics.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.18 no.12
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• pp.1139-1142
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• 2005

Recently, organic light emitting diodes(OLEDs) is widely used as one of the information display techniques. We synthesized 2-(2-hydroxyphenyl)benzoxazole($Zn(HPB)_2$). We studied the luminescent properties of OLEDs using $Zn(HPB)_2$. The ionization potential(IP) and the electron affinity(EA) of $Zn(HPB)_2$ investigated using cyclic-voltammetry(C-V). The IP and EA were 6.5 eV and 3.0 eV, respectively. The PL and EL spectra of $Zn(HPB)_2$ were observed at the wavelength of 450 nm. We used $Zn(HPB)_2$ as an emitting layer and hole blocking layer. At the experiment about hole blocking effect, we inserted $Zn(HPB)_2$ between emiting material layer(EML) and cathode, and between hole transport layer(HTL) and emitting material layer(EML). We measured current density-voltage and luminance-voltage characteristics at room temperature.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.07a
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• pp.447-448
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• 2005

Recently, organic light emitting diodes(OLEDs) is widely used as one of the information display techniques. We synthesized 2-(2-hydroxyphenyl)benzoxazole($Zn(HPB)_2$). We studied the luminescent properties of OLEDs using $Zn(HPB)_2$. The ionization potential(IP) and the electron affinity(EA) of $Zn(HPB)_2$ investigated using cyclic-voltammetry(C-V). The JP, EA and Eg were 6.5eV, 3.0eV and 3.5eV, respectively. The PL and EL spectra of $Zn(HPB)_2$ were observed at the wavelength of 4S0nm. We used $Zn(HPB)_2$ as an emitting layer and hole blocking layer. At the experiment about hole blocking effect, we inserted $Zn(HPB)_2$ between emitting material layer(EML) and cathode, and hole transport layer(HTL) and emitting material layer(EML). We measured current density-voltage and luminance-voltage characteristics at room temperature.