• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2003.05c
• /
• pp.261-264
• /
• 2003

In this paper, a disk-type piezoelectric transformer for the high power was investigated with the variation of road resistance. The diameter and thickness of a disk-type piezoelectric transformer was 45mm and 4mm, respectively. The piezoelectric ceramics was composed to PZT-PMN-PSN. The ratio of driving electrode and generating electrode is 2:1. The poling direction of driving part and generating part are the same. A voltage step-up ratio increased with increasing the load resistance, $R_L$, so it reached 60 under no road resistance. Also, the maximum efficiency of 97% was obtained.

• Journal of the Semiconductor & Display Technology
• /
• v.19 no.4
• /
• pp.18-21
• /
• 2020

Undetected wafer slip during the lift pin-down motion in semiconductor equipment may affect the center to edge variation, wafer warpage, and pattern misalignment in plasma equipment. Direct measuring of the amount of wafer slip inside the plasma process chamber is not feasible because of the hardware space limitation inside the plasma chamber. In this paper, we demonstrated a practice for the wafer lift pin-up and down motions with respect to the gear ratio, operating voltage, and pulse width modulation to maintain accurate wafer position using remote control linear servo motor with an experimentally designed chamber mockup. We noticed that the pin moving velocity and gear ratio are the most influencing parameters to be control, and the step-wised position control algorithm showed the most suitable for the reduction of wafer slip.

• Proceedings of the KIEE Conference
• /
• 2001.07e
• /
• pp.3-6
• /
• 2001

This paper is shows the configuration of the maximum power tracking control of Photo-voltaic and battery charge system. Up to now, the chopper system had the problem which a battery become a short life by reason of discontinuity of output current and its energy reduce. But in this paper, We propose the chopper system which maintain the successive output current and at the same time, control the maximum output location by change time-ratio using tracking of energy variation that occur because of the varied volume of insolation per a day and temperature.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.60 no.3
• /
• pp.544-551
• /
• 2011

This paper presents the circuit arrangement and effective control method of regenerative energy storage system for an electric vehicle using super-capacitors as the braking energy storage element. A bi-directional controlled current flow of the DC-DC converters with the capacitor bank is connected in parallel with battery, and is controlled so that the whole of the braking energy is effectively absorbed into the capacitors and released back to the electric motor upon acceleration. The converter needs the series-parallel switching circuit for making the best use of the series capacitors and for limiting the step-up ratio of the boost converter. The proposed methods are verified by computer simulation and experimental set-up. They are usefully applied to the electric vehicles such as green cars, electric motorcycles, bike, etc which are power- supplied by the electric batteries.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.27 no.8
• /
• pp.1122-1133
• /
• 2003

Numerical characteristics of implicit upwind schemes, such as upwind ADI, line Gauss-Seidel (LGS) and point Gauss-Seidel (LU) algorithms, for Navier-Stokes equations have been investigated. Time-derivative preconditioning method was applied for efficient convergence at low Mach/Reynolds number regime as well as at large grid aspect ratios. All the algorithms were expressed in approximate factorization form and von Neumann stability analysis was performed to identify stability characteristics of the above algorithms in the presence of high grid aspect ratios. Stability analysis showed that for high aspect ratio computations, the ADI and LGS algorithms showed efficient damping effect up to moderate aspect ratio if we adopt viscous preconditioning based on min-CFL/max-VNN time-step definition. The LU algorithm, on the other hand, showed serious deterioration in stability characteristics as the grid aspect ratio increases. Computations for several practical applications also verified these results.

• Journal of Power Electronics
• /
• v.13 no.4
• /
• pp.636-646
• /
• 2013

A single-phase tapped-inductor boost converter has been proposed previously. However, detailed characterization and performance analysis were not conducted. This paper presents a detailed characterization, performance analysis, and design expressions of a single-phase tapped-coupled-inductor boost converter. Expressions are derived for average and RMS input current as well as for RMS input and output capacitor current ripple. A systematic approach for sizing the tapped-coupled inductor, active switch, and output diode is presented; such approach has not been reported in related literature. This study reveals that sizing of the inductor has to be based on current ripple requirement, turns ratio, and load. Conditions that produce discontinuous inductor current are also discussed. Analysis of a non-ideal converter operating in continuous conduction mode is also conducted. The expression for the voltage ratio considering the coupling coefficient is derived. The suitability of the converter for high-voltage step-up applications is evaluated. Factors that affect the voltage boost ratio are also identified. The effects of duty ratio and load variation on the performance of the converter are also investigated. The theoretically derived characteristics are validated through simulations. Experimental results obtained at a low power level are included to validate the analytical and simulation results. A good agreement is observed among the analytical, simulation, and experimental results.

• Journal of Advanced Marine Engineering and Technology
• /
• v.41 no.1
• /
• pp.76-82
• /
• 2017

Since the introduction of electronically controlled engines and electric propulsion ships, the need for an uninterruptible power supply for emergency power supply devices that use batteries has gained importance. The bidirectional converter in such emergency power supply devices is a crucial component. This paper proposes, a topology for an improved DC-DC bidirectional converter that is characterized by a high voltage conversion ratio and low voltage stress of switches. To confirm the performance of the converter, a computer simulation was executed with PSIM software. The conversion ratio of the proposed converter was found to be four times higher than the conventional boost converter in step-up mode and one-fourth that of the conventional buck converter in step-down mode, and the voltage stress of the switches was one-fourth of the high-side voltage. Moreover, the proposed converter was confirmed to be able to distribute equal currents between two interleaved modules without using any extra current-sharing control method because of the charge balance of its blocking capacitors.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.3 no.4
• /
• pp.38-43
• /
• 1999

An experimental study was carried out, in order to set up the procedure for evaluation of hot fire test, to investigate the effect of mixture on combustion performance and combustion stability , and to determine the optimum design condition for designing the liquid rocket engine. $HNO_3$/Kerosene uni-element liquid rocket engine(thrust 24 $\iota{b}_f$, chamber pressure 200 psia) using impinging streams doublet injector was designed, and ground hot-fire test was carried out. To prevent or reduce the hard start during ignition period, two step ignition method was used. This was accomplished by maintaining about 25% of the designed operating pressure doting transient period, then chamber pressure was built up to the designed operating pressure. Maximum combustion efficiency was at O/F ratio 3.6, and combustion efficiency is decreased with increasing momentum ratio.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.18 no.3
• /
• pp.247-255
• /
• 2013

In this paper, a soft switching DC-DC converter for AC module type photovoltaic (PV) module integrated converter is proposed. A push-pull converter is suitable for a low voltage PV AC module system because the step-up ratio of a high frequency transformer is high and the number of primary side switches is relatively small. However, the conventional push-pull converters do not have high efficiency because of high switching losses by hard switching and transformer losses (copper and iron losses) by high turns-ratio of the transformer. In the proposed converter, primary side switches are turned on at zero voltage switching (ZCS) condition and turned off at zero current switching (ZVS) condition through parallel resonance between secondary leakage inductance of the transformer and a resonant capacitor. Therefore the proposed push-pull converter decreases the switching loss using soft switching of the primary switches. Also, the turns-ratio of the transformer can be reduced by half using a voltage-doubler of secondary side. The theoretical analysis of the proposed converter is verified by simulation and experimental results.

• ETRI Journal
• /
• v.38 no.6
• /
• pp.1240-1249
• /
• 2016

With the number of IP cores in a multicore system-on-chip increasing to up to tens or hundreds, the role of on-chip interconnection networks is vital. We propose a networks-on-chip-style bus network as a compromise and redefine the exploration problem to find the best IP tiling patterns and communication path combinations. Before solving the problem, we estimate the time complexity and validate the infeasibility of the solution. To reduce the time complexity, we propose two fast exploration algorithms and develop a program to implement these algorithms. The program is executed for several experiments, and the exploration time is reduced to approximately 1/22 and 7/1,200 at the first and second steps of the exploration process, respectively. However, as a trade-off for the time saving, the time cost (TC) of the searched architecture is increased to up to 4.7% and 11.2%, respectively, at each step compared with that of the architecture obtained through full-case exploration. The reduction ratio can be decreased to 1/4,000 by simultaneously applying both the algorithms even though the resulting TC is increased to up to 13.1% when compared with that obtained through full-case exploration.