• The Transactions of the Korean Institute of Power Electronics
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• v.17 no.1
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• pp.34-40
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• 2012

In this paper, voltage clamped tapped-inductor boost converter with high voltage conversion ratio is proposed. The conventional tapped-inductor boost converter has a serious drawback such as high voltage stresses across all power semiconductors due to the high resonant voltage caused by the leakage inductor of tapped inductor. Therefore, the dissipative snubber is essential for absorbing this resonant voltage, which could degrade the overall power conversion efficiency. To overcome these drawbacks, the proposed converter employs a voltage clamping capacitor instead of the dissipative snubber. Therefore, the voltage stresses of all power semiconductors are not only clamped as the output voltage but the power conversion efficiency can also be considerably improved. Moreover, since the energy stored in the clamp capacitor is transferred to the output side together with the input energy, the proposed converter can achieve the higher voltage conversion ratio than the conventional tapped-inductor boost converter. Therefore, the proposed converter is expected to be well suited to various applications demanding the high efficiency and high voltage conversion ratio. To confirm the validity of the proposed circuit, the theoretical analysis and experimental results of the proposed converter are presented.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.40 no.2
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• pp.162-172
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• 1991

In proportion to the capacity enlargement of the induction motor system controlled by current source inverter, the capacitance of the commutating capacitor is enlarged and then the spike value of output voltage is increased at the moment of charge and discharge. Moreover, the output currnet includes a number of harmonic components. Such voltage spike and harmonics generate the torque ripple and lead to bad effects on the performance of the induction motor. In this study, all the harmonics excluding 17th and 19th harmonics were mostly elimunated by adopting 18-phase Triple High Frequency Current Source Inverter(HFCSI), and the spike component of output voltage was reduced by adding the Voltage Clamping Circuit(VCC). As a result, the torque ripple and the commutation loss were reduced and the performance of the system was improved. Experiments for speed control were carried out in the tripple current source inverter system for induction motor drive. Overall system was controlled by ONE CHIP MICROCOMPUTER(INTEL 8751). Control circuits were simplified and good experimental results in the constant V/F control were obtained due to the flexibility of the microcomputer.

• Journal of Power Electronics
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• v.18 no.1
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• pp.277-288
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• 2018

Wireless inductive power transfer (IPT) technology is used in many applications today. A compact and high-frequency primary side inverter is one of the most important parts of a WPT system. In this study, a modified class EF-type voltage-fed multi-resonant inverter has been proposed for WPT application at a frequency range of 85-100 kHz. Instead of an infinite input choke inductor, a resonant inductor is used to reduce loss and power density. The peak voltage stress across the MOSFET has been reduced to almost 60% from a class-E inverter using a passive clamping circuit. A simple yet effective design procedure has been presented to calculate the various component values of the proposed inverter. The overall system is simulated using MATLAB/SimPowerSystem to verify the theoretical concepts. A 500-W prototype was built and tested to validate the simulated results. The inverter exhibited 90% efficiency at nearly perfect alignment condition, and efficiency reduced gradually with the misalignment of WPT coils. The proposed inverter maintains zero-voltage switching (ZVS) during considerable load changes and possesses all the inherent advantages of class E-type inverters.

• Journal of the Korean Institute of Telematics and Electronics C
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• v.36C no.5
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• pp.27-37
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• 1999

A CMOS ReadOut Integrated Circuit (ROlC) for InfraRed Focal Plane Array (IRFPA) detector is presented, which is a key component in uncooled thermal imaging systems. The ROIC reads out signals from $64\times64$ Barium Strontium Titanate (BST) infrared detector array, then outputs pixel signals sequentially after amplifying and noise filtering. Various design requirements and constraints have been considered including impedance matching, low noise, low power dissipation and small detector pitch. For impedance matching between detector and pre~amplifier, a new circuit based on MOS diode structure is devised, which can be easily implemented using standard CMOS process. Also, tunable low pass filter with single~pole is used to suppress high frequency noise. In additions, a clamping circuit is adopted to enhance the signal~to-noise ratio of the readout output signals. The $64\times64$ IRFPA ROIC is designed using $0.65-\mu\textrm{m}$ 2P3M (double poly, tripple metal) N~Well CMOS process. The core part of the chip contains 62,000 devices including transistors, capacitors and resistors on an area of about $6.3-mm\times6.7-mm$.

• Molecules and Cells
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• v.42 no.1
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• pp.45-55
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• 2019

The liver is involved in a wide range of activities in vertebrates and some other animals, including metabolism, protein synthesis, detoxification, and the immune system. Until now, various methods have been devised to study liver diseases; however, each method has its own limitations. In situ liver perfusion machinery, originally developed in rats, has been successfully adapted to mice, enabling the study of liver diseases. Here we describe the protocol, which is a simple but widely applicable method for investigating the liver diseases. The liver is perfused in situ by cannulation of the portal vein and suprahepatic inferior vena cava (IVC), with antegrade closed circuit circulation completed by clamping the infrahepatic IVC. In situ liver perfusion can be utilized to evaluate immune cell migration and function, hemodynamics and related cellular reactions in each type of hepatic cells, and the metabolism of toxic or other compounds by changing the composition of the circulating media. In situ liver perfusion method maintains liver function and cell viability for up to 2 h. This study also describes an optional protocol using density-gradient centrifugation for the separation of different types of hepatic cells, allowing the determination of changes in each cell type. In summary, this method of in situ liver perfusion will be useful for studying liver diseases as a complement to other established methods.

• Journal of Power Electronics
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• v.19 no.3
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• pp.702-713
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• 2019

Multilevel Inverters (MLIs) are widely used in medium voltage applications due to their various advantages. In addition, there are numerous types of MLIs for such applications. However, the diode-less 3-level (3L) T-type Neutral Point Clamped (NPC) MLI is the most advantageous due to its low conduction losses and high potential efficiency. The power circuit of a 3L T-type NPC is derived by the conventional two level inverter by a slight modification. In order to explore the MLI performance for various Pulse Width Modulation (PWM) schemes, this paper examines the operation of a 3L (five level line to line) T-type NPC MLI for various types of Multi-Carriers Pulse Width Modulation (MCPWM) schemes. These PWM schemes are compared in terms of their voltage profile, total harmonic distortion (THD) and conduction losses. In addition, a 3L T-type NPC MLI is also compared with the conventional NPC in terms of number of switches, clamping diodes, main diodes and capacitors. Moreover, the capacitor-balancing problem is also investigated using the Neutral Point Fluctuation (NPF) method with all of the MCPWM schemes. A 1kW 3L T-type NPC MLI is simulated in MATLAB/Simulink and implemented experimentally and its performance is tested with a 1HP induction motor. The results indicate that the 3L T-type NPC MLI has better performance than conventional NPC MLIs.

• Journal of Chest Surgery
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• v.38 no.1 s.246
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• pp.13-22
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• 2005

It has been known that pulsatile flow is physiologic and more favorable to tissue perfusion than nonpulsatile flow. The purpose of this study is to directly compare the effect of pulsatile versus nonpulsatile blood flow to renal tissue perfusion in extracorporeal circulation by using a tissue perfusion measurement system. Material and Method: Total cardiopulmonary bypass circuit was constructed to twelve Yorkshire swines, weighing 20$\~ $30 kg. Animals were randomly assigned to group 1 (n=6, non pulsatile centrifugal pump) or group 2 (n=6, pulsatile T-PLS pump). A probe of the tissue perfusion measurement system $(QFlow^{TM}-500)$ was inserted into the renal pa­renchymal tissue. Extracorporeal circulation was maintained for an hour at a pump flow of 2 L/min after aortic cross-clamping. Tissue perfusion flow of the kidney was measured at baseline (before bypass) and every 10 minutes after bypass. Serologic parameters were collected at baseline and 60 minutes after bypass. Result: Baseline parameters were not different between the groups. Renal tissue perfusion flow was substantially higher in the pulsatile group throughout the bypass (ranged 48.5$\~$ 64 in group 1 vs. 65.8$\~$88.3 mL/min/100 g in group 2, p=0.026$\~$ 0.45) The difference was significant at 30 minutes bypass $(47.5{\pm}18.3\;in\;group\;1\;vs.\;83.4{\pm}28.5$ mL/min/100 g in group 2, p=0.026). Serologic parameters including plasma free hemoglobin, blood urea nitrogen, and creatinine showed no differences between the groups at 60 minutes after bypass (p=NS). Conclusion: Pulsatile flow is more beneficial to tissue perfusion of the kidney in short-term extracorporeal circulation. Further study is suggested to observe the effects to other vital organs or long-term significance.

• Journal of Chest Surgery
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• v.32 no.6
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• pp.495-503
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• 1999

Background: We tested the technical feasibility of fetal cardiac bypass and collected baseline data on the fetal hemodynamics and placental functions related to the cardiopulmonary bypass in the fetal lamb model. Material and Method: Eleven fetuses at 120 to 150 days of gestation were subjected to bypass via trans-sternal approach with a 12 G pulmonary arterial cannula and 14 to 18 F venous cannula for 30 minutes. All ewes received general anesthesia with ketamine. In all the fetuses, no anesthetic agents were used except muscle relaxant. Eight served as a group in which placenta was excluded from the extracorporeal circulation by clamping the umbilical cord during the bypass(the oxygenator group) and in the remaining three, the placenta worked as the only source of oxygen supply(the placenta group). Observations were made every 10 minute during a 30-minute bypass and 30-minute post bypass period. No prostaglandin inhibitors were used both in ewes and in fetuses. Result: Weights of the fetuses ranged from 1.9 to 5.2 kg. In the oxygenator group, means of arterial pressure, PaO2, atrial pressure, heart rate, and bypass flow rate ranged 69.8 to 82.6 mmHg, 201.7 to 220.9 mmHg, 4.1 to 4.3 mmHg, 169 to 182/min, and 140.3 to 164.0 ml/kg/min, respectively during bypass, but rapid deterioration of the fetal cardiac functions and the placental gas exchange was observed after the cessation of bypass. In the placenta group, means of arterial pressure decreased from 44.7 to 14.4 mmHg and means of PaCO2 increased from 61.9 to 129.6 mmHg during bypass. Flow rate was suboptimal(74.3 to 97.0 ml/kg/min) during bypass. All hearts fibrillated immediately after the discontinuation of bypass. Conclusion: In this study, the technical feasibility of fetal cardiopulmonary bypass was confirmed in the fetal lamb model. However, further studies with modifications of the bypass including an addition of prostaglandin inhibitor, an application of the total spinal anesthesia on the fetus, a creation of more concise bypass circuit, and a use of active pump are mandatory to improve the outcome.