• Proceedings of the KIEE Conference
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• 1996.07a
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• pp.255-258
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• 1996

A new low conduction loss, low cost zero-voltage-transition power factor correction circuit(PFC) is presented. Conventional PFC which consists of a bridge diode and a boost converter(one switch) always has three semiconductor conduction drops. Two switch type PFCs reduces conduction loss by reducing one conduction drop but the cost is increased because of increased number of active switches. The proposed PFC reduces conduction loss with one switch, which allows low cost. Conduction loss improvement is a little bit less than that of two switch type, but very close up. Operation and features are comparatively illustrated and verified by simulation and experimental results of 1 kW laboratory prototype.

• Proceedings of the KIPE Conference
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• 2001.10a
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• pp.703-707
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• 2001

The demand for protection of power electronic applications has during the last couple of years increased regarding the high-power IGBT modules. Even with an active protection, a high power IGBT still has a risk of exhibiting a violent rupture in the case of a fault if IGBT Fuses do not protect it. By introducing fuses into the circuit this will increase the circuit inductance and slight increase the over-voltage during the turn-off of the diode and the IGBT. It is therefore vital when using fuses that the added inductance is kept at a minimum. This paper discuss three issues regarding the IGBT Fuse protection. First, the problem of adding inductance of existing High-Speed and new Typower fuses in DC-link circuit is treated, second a short discussion of the protection of the IGBT module is done, and finally, the impact of the high frequency loading on the current carrying capability of the fuses is presented.

• Proceedings of the KIPE Conference
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• 2003.07a
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• pp.269-274
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• 2003

본 논문에서는 2대의 다이오드 정류기에 부스트 컨버터를 이용하여 전류의 파형을 능동적으로 만들어 정현파의 입력전류를 얻는 새로운 방식의 고조파 저감방식을 제안한다. 제안한 당식으로 역률 1의 전원 품질을 얻을 수 있으며 입력측의 변동에 대한 출력전압의 조정도 가능하다. 또한 저감된 용량을 갖는 3상 오토 트랜스포머의 사용으로 기존의 $\Delta$-Y 변압기에 비해 KVA정격이 80$\%$ 절감되며 상간변압기도 필요 없다. 본 방식을 소형화와 고품질의 전원이 요구되는 통신용 정류기등에 적용하면 효과적이다. 제안한 방식의 동작원리, 제어 및 설계방법을 기술하고 1.5KW급 시작품으로부터의 실험결과를 제시한다.

• ETRI Journal
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• v.30 no.3
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• pp.480-482
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• 2008

A novel InGaAsP/InP buried-ridge waveguide laser diode structure is proposed and demonstrated for use as a single-mode laser. The lateral mode of the proposed device can be controlled by adjusting the composition and thickness of the InGaAsP layer grown over the active region. Stable single-mode operation without kinks or beam-steering is achieved successfully with lateral and transverse in the junction plane even for the device with the ridge width of 9 ${\mu}m$ up to an injection current of 500 mA.

• Journal of Advanced Marine Engineering and Technology
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• v.29 no.7
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• pp.795-800
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• 2005

The optical properties of $ZnS_{y}Se_{1-x-y}:Te_x\;(x\;<\;0.08,\;y\∼0.11$) alloys grown by molecular beam epitaxy (MBE) have been investigated by photoluminescence (PL) and PL-excitation (PLE) spectroscopy. Good optical properties and high crystal quality were established with lattice match condition to GaAs substrate. At room temperature, emission in the visible spectrum region from blue to green was obtained by varying the Te content of the ZnSSe:Te alloy. The efficient blue and green emission were assigned to $Te_{1}$Tel and $Te_{n}$ (n$\geq$2) cluster bound excitons, respectively. Bright blue (462 nm) and green (535 nm) light emitting diodes (LEDs) have been developed using ZnSSe:Te system as an active layer.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.35D no.8
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• pp.24-30
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• 1998

A blue LED of $In_{x}Ga_{1-x}N$ multiple quantum well structure which had the blue emission spectrum of donor-acceptor pair transition generated form Si-Zn co-doped $In_{x}Ga_{1-x}N$ active layer, was fabricated. The $In_{x}Ga_{1-x}N$ MQW heterojunction LED structure was grown by MOCVD on the sapphire substrate with (0001) surface orientation at 800.deg. C. The fabricated LED exhibited forward cut-in voltage of 4~4.5V and reverse breakdown voltage of -13V. Its optical chracteristics showed that the center wavelength of peak emission occurred at 460nm and the optical intensity was increased linearly with respect to the injected electrical current above 5mA.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.21 no.6
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• pp.503-508
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• 2008

In order to reduce the piezoelectric field originated from the well layer which resides in InGaN/GaN light emitting diode, InGaN/GaN superlattice buffer layers were grown at the bottom and the top of the active layer. Measuring the photoluminescence spectra with different reverse bias voltages clearly revealed the condition of the flat band under which the transition energy is maximized and the linewidth is minimized. Accordingly, the piezoelectric field of $In_{0.15}Ga_{0.85}N$ in our sample was estimated as -1.08 MV/cm. It is less than half the value reported in the previous studies, and it is evidenced that the strain has reduced due to the superlattice buffer layers.

• Journal of Advanced Marine Engineering and Technology
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• v.27 no.1
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• pp.33-41
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• 2003

The optical properties of $ZnS_ySe_{1-\chi-y}:Te_{\chi}(\chi<0.08,y~0.11)$ alloys grown by molecular beam epitaxy (MBE) have been investigated by photoluminescence (PL) and PL-excitation (PLE) spectroscopy. Good optical properties and high crystal quality were established with lattice match condition to GaAs substrate. At room temperature, emission in the visible spectrum region from blue to green was obtained by varying the Te content of the ZnSSe:Te alloy. The efficient blue and green emission were assigned to $Te_1 and Te_n(n\geq2)$cluster bound excitons, respectively. Bright green (535 nm) and blue (462 nm) light emitting diodes (LEDs) have been developed using ZnSSe:Te system as an active layer. The turn-on voltage of 2.1 V in current-voltage characteristics is very small compared to that of commercial InGaN-based LEDs (>3.4 V), indicating the formation of a good ohmic contact due to the optimized p-ZnSe/p-ZnTe multi-quantum well (MQW) superlattice electrode layers.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 1999.05a
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• pp.330-334
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• 1999

This paper presents a new transient voltage blocking device (TBD) for commucation 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, the new TBD, which consists of a gas tube, avalanche diodes and junction type field effect transistors (JFETs), was designed and fabricated JFETs were used as an active non-linear element and a high speed switching diode with low capacitance limits high current. Therefore the avalanche diodes with low energy capacity are protected from the high current, and the TBD has a very small input capacitance. From the performance test using surge generator, which can produce 1.2/50${\mu}\textrm{s}$ 4.2 k$V_{max}$, 8/20${\mu}\textrm{s}$ 2.1 kA$\sub$max/, it is confirmed that the proposed TBD has an excellent protection performance in tight clamping voltage and limiting current characteristics.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.52 no.12
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• pp.632-640
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• 2003

In conventional Zero-Voltage-Transition(ZVT) PWM converters, zero-voltage turn-on and turn-off for main switch without increasing voltage/current stresses is achieved at a fixed frequency. The switching loss, stress, and noise, however, can't be minimized because they adopt auxiliary switches turned off under hard-switching condition. In this paper, new ZVS-PWM converters of which both active and passive switches are always operating with soft-switching condition are proposed. Therefore, the proposed ZVS-PWM converters are most suitable for avionics applications requiring high-power density. Breadboarded ZVS-PWM boost converters using power MOSFET are constructed to verify theoretical analysis.