• Korean Journal of Animal Reproduction
• /
• v.20 no.4
• /
• pp.467-472
• /
• 1997

This study was conducted to determine the optimal DC voltage for NT of in vivo donor embryo nuclei and investigate the effect of donor embryo guality on fusion and in vitro development of NT embryos . Recpient oocytes were enucleated 25~27h after IVM and further cuitured for 18~20h prior to fusion for oocyte aging. Donor embryos of molura stage were recovered from superovulated heifers and classified l into good and low quality group. Their nuclei were transferred in to the emucleated oocytes 42~44h post-IVM and fused 43-45h post-IVM with a single 0.75kV /cm or 1.0kV /cm DC voltage for 70${\mu}\textrm{A}$sec. The fusion rate of oocytes was not different between two DC voltages. However, the cleavage and M + B developmnent was more high at 1.0kV /cm DC voltage and the proportion of M+B was 19.0% at 0.75kV /cm DC and 29.4% at 1.0kV /cm DC voltage. Donor embryo qualtiy did not greatly affect the fusion and cleavage of NT oocytes, but none of NT embryos derived from low embryo quatity reached the morula stage. The results indicate that the most suitable DC v voltage for electrofusion of in vivo donor muclei was a single 1.0kV /cm DC voltage and donor embryo quality was an important factor affecting the development in vitro of NT embryos.

• The Journal of the Korea institute of electronic communication sciences
• /
• v.18 no.4
• /
• pp.617-624
• /
• 2023

Recently, miniaturization and low power consumption of electronic products and improved efficiency and power factor improvement have become a matter of great interest. In this paper, an AC-DC converter based on PWM control was designed and made. The AC-DC converter is designed with a structure in which one rectifier circuit and one output voltage control circuit are connected in series. The rectifier circuit is a diode-based single phase full-wave current circuit and the output voltage control circuit is a DC-DC conversion circuit based on PWM control. Arduino was used as the main control device for PWM control, and LCD was configured at the output stage so that the control result could be checked. The error between the output voltage displayed on the oscilloscope and LCD and the target output voltage was confirmed through repeated experiments with the test circuit, and the validity of the proposed design methodology was confirmed by showing an error rate of about 5% based on the oscilloscope measurement value.

• Proceedings of the IEEK Conference
• /
• 1999.06a
• /
• pp.353-356
• /
• 1999

A 3.3V PLL(Phase Locked loop) is designed for a high frequency, low voltage, and low power applications. This paper proposes a new PLL architecture to improve voltage to frequency linearity of VCO(Voltage controlled oscillator) with new delay cell. The proposed VCO operates at a wide frequency range of 30MHz~1㎓ with a good linearity. The DC-DC voltage up/down converter is utilized to regulate the control voltage of the two-stage VCO. The designed PLL architecture is implemented on a 0.6${\mu}{\textrm}{m}$ n-well CMOS process. The simulation results show a locking time of 2.6$\mu$sec at 1Hz, Lock in range of 100MHz~1㎓, and a power dissipation of 112㎽.

• Smart Structures and Systems
• /
• v.26 no.4
• /
• pp.521-531
• /
• 2020

In this paper, a new interleaved high step-up converter with low voltage stress on the switches is proposed. In the proposed converter, soft switching is provided for all switches by just one auxiliary switch, which decreases the conduction loss of auxiliary circuit. Also, the auxiliary circuit is expanded on the converter with more input branches. In the converter all main switches operate under zero voltage switching condition and auxiliary switch operate under zero current switching condition. Because of the interleaved structure, the reliability of converter increases and input current ripples decreases. The clamp capacitor in the converter not only absorb the voltage spikes across the switch due to leakage inductance, but also improve voltage gain. The proposed converter is fully analyzed and to verify the theoretical analysis, a 100 W prototype was implemented. Also, to show the effectiveness of auxiliary circuit on conduction EMI, EMI of the proposed converter comprised with hard switching counterpart.

• ETRI Journal
• /
• v.44 no.4
• /
• pp.695-707
• /
• 2022

As for the insufficient nature of the fossil fuel resources, the renewable energies as alternative fuels are imperative and highly heeded. To deliver the required electric power to the industrial and domestic consumers from DC renewable energy sources like fuel cell (FC), the power converter operates as an adjustable interface device. This paper suggests a new boost structure to provide the required voltage with wide range gain for FC power source. The proposed structure based on the boost converter and the quazi network, the so-called SBQN, can effectively enhance the FC functionality against its high operational sensitivity to experience low current ripple and also propagate voltage and current with low stress across its semiconductors. Furthermore, the switching power losses have been decreased to make this structure more durable. A full operational analysis of the proposed SBQN and its advantages over the conventional and famous structures has been compared and explained. Furthermore, a prototype of the single-phase converter has been constructed and tested in the laboratory.

• Journal of the Korean Society of Industry Convergence
• /
• v.24 no.5
• /
• pp.641-644
• /
• 2021

Wearable devices and IoT are being utilized in various fields, where all systems are developing in the direction of multi-functionality, low power consumption, and high speed. In this paper, we propose a DC -DC Step-down C onverter for IoT smart devices. The proposed DC -DC Step-down converter is composed of a control block of the power supply stage. It also consists of an overheat protection circuit, under-voltage protection circuit, an overvoltage protection circuit, a soft start circuit, a reference voltage circuit, a lamp generator, an error amplifier, and a hysteresis comparator. The proposed DC-DC converter was designed and fabricated using a Magnachip / Hynix 180nm CMOS process, 1-poly 6-metal, the measured results showed a good match with the simulation results.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.26 no.2
• /
• pp.112-119
• /
• 2021

This study proposes a design method of high-power-density and high-efficiency low-voltage DC-DC converters using SiC MOSFET and the optimized planar transformer design procedure based on the figure-of-merit. The secondary rectifying circuit of the phase-shifted full-bridge converter is compared to achieve high power density and high efficiency, and the phase-shifted full bridge converter with a current-doubler rectifier is selected. The planar transformer is designed by the proposed optimized design procedure and verified by FEA simulation. To validate the proposed design method, experimental results from a 3 kW prototype are provided. The prototype achieved 95.28% maximum efficiency and a power density of 2.98 kW/L.

• Proceedings of the KIPE Conference
• /
• 2019.07a
• /
• pp.348-349
• /
• 2019

본 논문은 전기자동차용 8.1kW/L의 높은 전력밀도를 갖는 저전압 DC-DC 컨버터(Low-voltage DC-DC converter, LDC)의 설계 방법을 제안한다. 넓은 전압범위에서 높은 전력밀도를 성취하기 위해 위상천이 풀-브릿지(Phase Shift Full-Bridge, PSFB) 컨버터의 2차측 토폴로지 후보군의 비교를 통해 전류-더블러 토폴로지로 토폴로지가 선정되었다. 또한 자속 상쇄 기법이 적용된 매트릭스 변압기를 적용한 PSFB 컨버터와 냉각기의 구조설계를 통해 8.1kW/L의 전력밀도를 달성하였으며 1.8kW 시작품을 제작하여 성능을 검증하였다.

• Journal of Sensor Science and Technology
• /
• v.26 no.5
• /
• pp.331-337
• /
• 2017

A readout circuit for a tactile sensor pad based on force sensing resistors was proposed, which was composed of an analog signal conditioning circuit and a digital circuit with a microcontroller. The conventional signal conditioning circuit has a dc offset voltage in the output signal, which results from the reference voltage applied to the FSR devices. The offset voltage reduces the dynamic range of the circuit and makes it difficult to operate the circuit under a low voltage power supply. In the proposed signal conditioning circuit, the dc offset voltage was removed completely. The microcontroller with A/D converter and D/A converter was used to enlarge the measurement range of pressure. For this, the microcontroller adjusts the FSR reference voltage according to the resistance magnitude of FSR under pressure. The operation of the proposed readout circuit which was connected to a tactile sensor pad with $5{\times}10$ FSR array was verified experimentally. The experimental results show the proposed readout circuit has the wider measurement range of pressure than the conventional circuit. The proposed circuit is suitable for low voltage and low power applications.

• Journal of Power Electronics
• /
• v.8 no.4
• /
• pp.309-316
• /
• 2008

In this paper, new topology is proposed that can dramatically reduce the converter power rating and increase the efficiency of total PV system. Since the output voltage of PV module has very wide voltage range, in general, the DC/DC converter is used to get constant high DC voltage. According to analysis of PV characteristics, in proposed topology, only 20% power of total PV system power is needed for DC/DC converter. DC/DC converter used in proposed topology has flat efficiency curve at all load range and very high efficiency characteristics. The total system efficiency is the product of that of converter and that of inverter. In proposed topology, because the converter efficiency curve is flat all load range, the total system efficiency at the low power range is dramatically improved. The proposed topology is implemented for 200kW PCS system. This system has only three DC/DC converters with 20kW power rating each other. It is only one-third of total system power. The experiment results show that the proposed topology has good performance.