• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.60 no.12
• /
• pp.2265-2269
• /
• 2011

1 kV high-voltage GaN Schottky diode is realized using GaN-on-Si template by oxidizing Ni-Schottky contact. The Auger electron spectroscopy (AES) analysis revealed the formation of $NiO_x$ at the top of Schottky contact. The Schottky contact was changed to from Ni/Au to Ni/Ni-Au alloy/Au/$NiO_x$ by oxidation. Ni diffusion into AlGaN improves the Schottky interface and the trap-assisted tunneling current. In addition, the reverse leakage current and the isolation-leakage current are efficiently suppressed by oxidation. The isolation-leakage current was reduced about 3 orders of magnitudes. The reverse leakage current was also decreased from 2.44 A/$cm^2$ to 8.90 mA/$cm^2$ under -100 V-biased condition. The formed group-III oxides ($AlO_x$ and $GaO_x$) during the oxidation is thought to suppress the surface leakage current by passivating surface dangling bonds, N-vacancies and process damages.

• Journal of Power Electronics
• /
• v.16 no.5
• /
• pp.1689-1697
• /
• 2016

Continuous conduction mode (CCM) boost converters are commonly used in home appliances and various industries because of their simple topology and low input current ripples. However, these converters suffer from several disadvantages, such as hard switching of the active switch and reverse recovery problems of the output diode. These disadvantages increase voltage stresses across the switch and output diode and thus contribute to switching losses and electromagnetic interference. A new topology is presented in this work to improve the switching characteristics of CCM boost converters. Zero-current turn-on and zero-voltage turn-off are achieved for the active switches. The reverse-recovery current is reduced by soft turning-off the output diode. In addition, an input current sensorless control is applied to the proposed topology by pre-calculating the duty cycles of the active switches. Power factor correction is thus achieved with less effort than that required in the traditional method. Simulation and experimental results verify the soft-switching characteristics of the proposed topology and the effectiveness of the proposed input current sensorless control.

• The Transactions of the Korean Institute of Electrical Engineers
• /
• v.33 no.8
• /
• pp.289-298
• /
• 1984

The single phase induction motor is recently requested to meet a broad speed control and smooth forward and reverse operation due to the multifarious usages. This paper deals with two phase operation of a two winding motor by reference current adaptive inverter which can supply the currents to satisfy the balanced oeration into the main and auxiliary winding through the entire operational region. According to the roposed system, the starting, forward and reverse and variable speed control of a two winding motor eliminated the capacitor from the capacitor-run motor is also possible. The formation and its principle of the reference current adaptive inverter and characteristic analysis of the motor fed by this apparatus are described in this paper. Excellent agreement with the measured results and calculated values by computer simulation is obtained.

• ETRI Journal
• /
• v.30 no.6
• /
• pp.833-843
• /
• 2008

The effect of forward and reverse electrostatic discharge (ESD) on the electro-optical characteristics of oxide vertical-cavity surface-emitting lasers is investigated using a human body model for the purpose of understanding degradation behavior. Forward ESD-induced degradation is complicated, showing three degradation phases depending on ESD voltage, while reverse ESD-induced degradation is relatively simple, exhibiting two phases of degradation divided by a sudden distinctive change in electro-optical characteristics. We demonstrate that the increase in the threshold current is mainly due to the increase in leakage current, nonradiative recombination current, and optical loss. The decrease in the slope efficiency is mainly due to the increase in optical loss.

• Proceedings of the Korea Society of Information Technology Applications Conference
• /
• 2005.11a
• /
• pp.99-102
• /
• 2005

In the paper, a proposed VCO based on bondwire inductances and nMOS varactors was implemented in a standard $0.25\;{\mu}m$ CMOS process. Using the new drain current model and a propagation delay time model equations, the operation speed of CMOS gate will predict the dependence on the load capacitance and the depth of oxide, threshold voltage, the supply voltage, the channel length. This paper describes the result of simulation which calculated a gate propagation delay time by using new drain current model and a propagation delay time model. At the result, When the reverse bias voltage on the substrate changes from 0 voltage to 3 voltage, the propagation delay time is appeared the delay from 0.8 nsec to 1 nsec. When the reverse voltage is biased on the substrate, for reducing the speed delay time, a supply voltage has to reduce. The $g_m$ value of MOSFET is calculated by using new drain current model.

• Journal of the Institute of Electronics Engineers of Korea SC
• /
• v.47 no.2
• /
• pp.50-54
• /
• 2010

Soft recovery (SR) quasi-resonant converter (QRC) including a Folding snubber network (FSN) is introduced. It is obtained by combining normal quasi-resonant converter with folding snubber network of which the surrounding components are composed of passive devices only (diodes and capacitors). The reverse recovery loss of the main rectifier diode is eliminated by this method utilizing quasi resonance with Folding snubber network. By realizing soft switching condition, the proposed converter has PWM capability with high efficiency and is suitable for high output current and high power DC to DC converter application.

• Journal of Electrochemical Science and Technology
• /
• v.7 no.4
• /
• pp.293-297
• /
• 2016

Here we propose a new equation by which we can estimate the baseline for measuring the peak current of the reverse curve in a cyclic voltammogram. A similar equation already exists, but it is a linear algebraic equation that over-simplifies the voltammetric curve and may cause unpredictable errors when calculating the baseline. In our study, we find a quadratic algebraic equation that acceptably reflects the complexity included in a voltammetric curve. The equation is obtained from a laborious numerical analysis of cyclic voltammetry simulations using the finite element method, and not from the closed form of the mathematical equation. This equation is utilized to provide a virtual baseline current for the reverse peak current. We compare the results obtained using the old linear and new quadratic equations with the theoretical values in terms of errors to ascertain the degree to which accuracy is improved by the new equation. Finally, the equations are applied to practical cyclic voltammograms of ferricyanide in order to confirm the improved accuracy.

• Proceeding of Spring/Autumn Annual Conference of KHA
• /
• 2011.04a
• /
• pp.290-295
• /
• 2011

The purpose of this paper was to study on the attitudes about Reverse-Mortgage among Baby Boomers to offer the basis for revitalization of Reverse-Mortgage. Social survey research using a questionnaire was conducted among the babyboomer's living in Seoul area from September $30^{th}$ to October $14^{th}$. The data from 102 respondents were analyzed using SPSS PASW 18.0. The main findings were as followings 1) although 64% of the respondents prefered to type which could withdraw temporary cash, but main factor that affected the use was a stability in one's old age 2) 72% of respondents thought adequate age for application was over 66. So lowering the qualification of age looked not need for revitalization 3) babyboomer's said that they would use reverse-mortgage if they couldn't get benefit from other pension inspite of getting lower recognition on house inheritance. It was be cause they regarded Reverse-Mortgage as a final step. In conclusion, current qualification and limit for withdraw looks adequate but it need public relations about its merit unlike other pension. And it has to emphasize its stability so that baby boomer can feel easy from holding a mortgage on their house.

• Journal of Hydrogen and New Energy
• /
• v.17 no.2
• /
• pp.133-140
• /
• 2006

The performance of proton exchange membrane fuel cell was decreased by reverse voltage using fuel starvation. Performance decrease in local area could be affected by duration and extent of reverse voltage. Hydrogen and air stoichiometic ratio was used to find the experimental condition of abrupt voltage decrease. LabVIEW was used to make control logic of automatic load off system in preset voltage. Reverse voltage experiment was done down to -1.2 V at constant current condition. When fuel cell voltage was reached to preset voltage, electronic load was disconnected to make open circuit voltage for 1 minute. Fuel cell performance was checked every 5 cycle and the degree of performance decrease and/or recovery was estimated. Ohmic resistance and charge transfer resistance were increased and platinum surface area was reduced 41% after reverse voltage experiment.

• Journal of Power Electronics
• /
• v.19 no.3
• /
• pp.827-834
• /
• 2019

Wireless power transfer via coupled magnetic resonances has been a hot research topic in recent years. In addition, the number of related devices has also been increasing. However, reverse signals transfer is often required in addition to wireless power transfer. The structure of the circuit for a wireless power transfer system via coupled magnetic resonances is analyzed. The advantages and disadvantages of both parallel compensation and series compensation are listed. Then the compensation characteristics of the inductor, capacitor and resistor were studied and an appropriate compensation method was selected. The reverse signals can be transferred by controlling the compensation of the resistor. In addition, it can be demodulated by extracting the change of the primary current. A 3.3 MHz resonant frequency with a 100 kHz reverse signals transfer system platform was established in the laboratory. Experimental results demonstrate that wireless power and reverse signals can be transferred synchronously.