• Journal of the Korean Vacuum Society
• /
• v.14 no.1
• /
• pp.7-16
• /
• 2005

Oil-Hydraulic pump consisting of swing twin-cylinder becomes to be used as a next generation of low vacuum pump. However, there is no enough flow-analysis for design improvement. It is essential to develope a numerical method for flow-analysis before manufacturing, in economic sense. Using a commercial code (Fluent), developed for flow-analysis, useful informations for design of pump were provided. Two-dimensional analysis has been performed to investigate the flow parameters such as pressure and velocity distributions between the swing twin-cylinder and the fixed cylinder. This numerical method will be used to design a better performance of pump consisting of swing twin-cylinder.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.15 no.1
• /
• pp.50-58
• /
• 2003

An analytical study was carried out to investigate the performance of an oil pumping system of a variable speed compressor using a commercial CFD program. The simulations for the oil supplying system with the oil and air mixture were performed by varying compressor speed from 40 Hz to 90 Hz. Comparing the predicted with the measured data on the modified scroll compressor validated the simulation model. The predicted results were consistent with the test data with a maximum deviation of 12.8%. The oil flow rate significantly increased with a rise of compressor speed due to a higher oil flow rate from the swing pump and a greater centrifugal force on oil gallery.

• Journal of the Institute of Electronics Engineers of Korea SD
• /
• v.45 no.8
• /
• pp.44-47
• /
• 2008

In this paper, a new circuit is proposed to minimize the charging and discharging current mismatch in charge pump for UWB PLL application. By adding a common-gate and a common-source amplifier and building the feedback voltage regulator, the high driving charge pump currents are accomplished. The proposed circuit has a wide operation voltage range, which ensures its good performance under the low power supply. The circuit has been implemented in an IBM 0.13um CMOS technology with 1.2V power supply. To evaluate the design effectiveness, some comparisons have been conducted against other circuits in the literature.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.22 no.6
• /
• pp.803-812
• /
• 1998

In this study, testing equipment with which several kinds of valves can be tested was composed. Two kinds of tilting check valves and a swing check valve were tested to analyze their dynamic characteristics. The results of the experiment showed that the tilting check valves protected the pump but that the swing check valve could not protect the pump when the reverse flow rate was high. Also the dynamic equation of the tilting check valve was formulated and simulated using system characteristic constant t$_{c}$ and one method of predicting t$_{c}$ by comparing the results of the simulation with the results of the experiment was proposed.sed.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.13 no.6
• /
• pp.2479-2483
• /
• 2012

This paper discusses the development of a personal compact oxygen generator for portable and mobility. The compact oxygen generator is operated with vacuum swing absorption by compact vacuum pump. The components of oxygen generator is composed on the miniaturization and weight reduction, and it is optimized by discharge pump speed, nozzle diameter and 3-way valve interval. In 0.5mm of nozzle diameter, $O_2$ concentration is approximately 37%, and flow rate is $1{\ell}$/min. On the 30cm away from the nozzle, $O_2$ concentration is increased approximately 0.5%.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
• /
• v.13 no.5
• /
• pp.359-369
• /
• 2020

In this paper, we proposed a charge pump (CP) circuit that has a wide operating range while reducing the current mismatch for the PLL that generates the main clock of the CMOS X-Ray detector. The operating range and current mismatch of the CP circuit are determined by the characteristics of the current source circuit for the CP circuit. The proposed CP circuit is implemented with a wide operating current mirror bias circuit to secure a wide operating range and a cascode structure with a large output resistance to reduce current mismatch. The proposed wide operating range cascode CP circuit was fabricated as a chip using a 350nm CMOS process, and current matching characteristics were measured using a source measurement unit. At this time, the power supply voltage was 3.3 V and the CP circuit current ICP = 100 ㎂. The operating range of the proposed CP circuit is △VO_Swing=2.7V, and the maximum current mismatch is 5.15 % and the maximum current deviation is 2.64 %. The proposed CP circuit has low current mismatch characteristics and can cope with a wide frequency range, so it can be applied to systems requiring various clock speed.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.19 no.8
• /
• pp.843-849
• /
• 2009

The reliable operation of a swing check valve in the main feed water system of a power plant is most essential for successful shout-down process. A failure to close the valve at proper time often leads to the instability of the main feed water system, or even to an emergency stop of the power plant. In reality it is a very difficult task to monitor the behavior of a swing check valve. Furthermore it is impossible to see the motion of the valve. In this work two measurements were carried out simultaneously to determine the precise valve closure time. The dynamic pressure measurements were made at the inlet and outlet regions of the swing check valve. The transient vibration of the valve housing in the direction of water flow was also measured, which enabled the measurement of the transient vibration of the valve housing near valve closure. By comparing the results produced from these measurements the precise valve closure time could be determined. By carrying out order tracking technique using the dynamic pressure signals and pump rpm signal, the complicated dynamic problems inside the main feed water system can be more easily dealt with. This measurement scheme might be implemented in a power plant on a real-time basis without much difficulty. If this could be implemented, valuable information essential for shut-down operations can readily be passed on to the main control room. The feasibility of this implementation was demonstrated by this experimental work.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.39 no.2
• /
• pp.211-217
• /
• 2015

Emission gas regulations and constantly increasing fuel costs call for the worldwide use of environmentally friendly and energy-efficient machines in industry. To meet these requirements, a hybrid excavator prototype has been developed that incorporates an electric swing motor, engine assist motor, and ultra-capacitor module into a conventional hydraulic excavator of the 22-ton class. This paper mainly describes a few techniques to optimize its energy efficiency. These include 1) controlling the engine speed in proportion to the load torque, 2) controlling the pump displacement when driving the electric swing system, 3) managing the ultra-capacitor voltage to minimize the electrical energy loss, and 4) reducing the cooling fan speed to improve the energy efficiency of the system.

• Journal of the Institute of Electronics Engineers of Korea SD
• /
• v.47 no.2
• /
• pp.94-99
• /
• 2010

This paper presents a charge pump architecture for correcting the current mismatch due to the PVT variation. In general, the current mismatch of the charge pump should be minimized to improve the phase noise and spur performance of the PLL. In order to correct the current mismatch of the charge pump, the current difference is detected by the replica charge pump and fed back into the main charge pump. This scheme is very simple and guarantees the high accuracy compared with the prior works. Also, it shows a good dynamic performance because the mismatch is corrected continuously. It is implemented in 0.13um CMOS process and the die area is $100{\mu}m\;{\times}\;160{\mu}m$. The voltage swing is from 0.2V to 1V at supply voltage of 1.2V. The charging and discharging currents are $100{\mu}A$, respectively and the current mismatch due to the PVT variation is less than 1%.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
• /
• v.15 no.2
• /
• pp.144-151
• /
• 2022

In this paper, a 1.5V 256kb eFlash memory IP with low area DC-DC converter is designed for battery application. Therefore, in this paper, 5V NMOS precharging transistor is used instead of cross-coupled 5V NMOS transistor, which is a circuit that precharges the voltage of the pumping node to VIN voltage in the unit charge pump circuit for the design of a low-area DC-DC converter. A 5V cross-coupled PMOS transistor is used as a transistor that transfers the boosted voltage to the VOUT node. In addition, the gate node of the 5V NMOS precharging transistor is made to swing between VIN voltage and VIN+VDD voltage using a boost-clock generator. Furthermore, to swing the clock signal, which is one node of the pumping capacitor, to full VDD during a small ring oscillation period in the multi-stage charge pump circuit, a local inverter is added to each unit charge pump circuit. And when exiting from erase mode and program mode and staying at stand-by state, HV NMOS transistor is used to precharge to VDD voltage instead of using a circuit that precharges the boosted voltage to VDD voltage. Since the proposed circuit is applied to the DC-DC converter circuit, the layout area of the 256kb eFLASH memory IP is reduced by about 6.5% compared to the case of using the conventional DC-DC converter circuit.