• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.21 no.3
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• pp.96-106
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• 2007

The terminal voltage of a synchronous generator is maintained by the field current control of excitation system. Generally AC/DC converter which is component of AVR(Automatic Voltage Regulator) system for excitation current control is connected to diode rectifier and DC/DC converter system. In the case of diode rectifier system of phase controlled converter as AC/DC converter have low power factor and harmonics of lower order in the line current. In this paper, two stage three phase PWM AC/DC converter is studied to solve these problems. The characteristics of a proposed converter reduces the harmonics and reactive power of the distribution line and has fast dynamic response in transient period using boost converter and current control mode buck converts. The proposed method is verified by the computer simulation and experimental results in prototype generation system.

• Journal of Power Electronics
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• v.10 no.3
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• pp.235-244
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• 2010

This paper presents a new isolated soft-switching bidirectional buck-boost inverter for fuel cell applications. The buck-boost inverter combines an isolated DC-DC converter with a conventional inverter to implement buck-boost DC-DC and DC-AC conversion. The main switches achieve zero voltage switching and zero current switching by using a novel synchronous switching SVPWM and the volume of the transformer in the forward and fly-back mode is also minimized. This inverter is suitable for wide input voltage applications due to its high efficiency under all conditions. An active clamping circuit reduces the switch's spike voltage and regenerates the energy stored in the leakage inductance of the transformer; therefore, the overall efficiency is improved. This paper presents the operating principle, a theoretical analysis and design guidelines. Simulation and experimental results have validated the characteristics of the buck-boost inverter.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2002.11a
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• pp.151-156
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• 2002

The output voltage of Synchronous Generator is regulated constantly by field current control in excitation system. A synchronous generator is equipped with an automatic voltage regulator(AVR), which is responsible for keeping the constant output voltage under normal operating conditions about various levels. High frequency PWM converter (Current Mode Control Buck converter) type excitation system for synchronous generator is able to sustain output voltage level properly when the fault condition happened. This paper deals with the design and evaluation of the excitation system controller for a synchronous generator to improve the steady state and transient stability. The simulation and experimental results show that the proposed excitation system is improve the respons time by the AVR(automatic voltage regulator) of 50kW synchronous generator that is applied the current mode control excitation system.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.43 no.5 s.311
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• pp.28-35
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• 2006

This paper presents a new 3.3-1 V synchronous buck DC/DC converter that employs CMOS operational transconductance amplifiers (OTAs) as circuit-building blocks. An error amplifier OTA in a PWM circuit is compensated for to improve temperature stability. The temperature coefficient of the transconductance gain of the compensated OTA is less than $150\;ppm/^{\circ}C\;over\;0-100^{\circ}C$. The HSPICE simulation results of the $0.3{\mu}m$ standard CMOS technology show that the efficiency of the proposed converter is as high as 80% in the load current range of 40-125 mA. These results show that the proposed converter is adequate for use in battery-operated systems.

• JSTS:Journal of Semiconductor Technology and Science
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• v.12 no.2
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• pp.186-192
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• 2012

Half-rail stacked drivers are used to reduce power consumption of the drivers for synchronous buck converters. In this paper, the stacked driver is optimized by matching the average charging and discharging currents used by high-side and low-side drivers. By matching the two currents, the average intermediate bias voltage can remain constant without the aid of the voltage regulator as long as the voltage ripple stays within the window defined by the hysteresis of the regulator. Thus the optimized driver in this paper can minimize the power consumption in the regulator. The current matching requirement yields the value for the intermediate bias voltage, which deviates from the half-rail voltage. Furthermore the required capacitance is also reduced in this design due to decreased charging current, which results in significantly reduced die area. The detailed analysis and design of the stacked driver is verified through simulations done using 5V MOSFET parameters of a typical 0.35-${\mu}m$ CMOS process. The difference in power loss between the conventional half-rail driver and the proposed driver is less than 1%. But the conventional half-rail driver has excess charge stored in the capacitor, which will be dissipated in the regulator unless reused by an external circuit. Due to the reduction in the required capacitance, the estimated saving in chip area is approximately 18.5% compared to the half-rail driver.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.49 no.9
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• pp.590-597
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• 2000

Design of single state AC-DC converter with high power factor for low level applications is proposed. The proposed converter is obtained from the integration of a buck-boost converter and the half-bridge DC-DC converter. This converter gives the good power factor correction low line current harmonic distortions and tight output voltage regulations. This converter also has a high efficiency by employing an soft switching method and synchronous rectifier. The modelling and detailed analysis for the proposed converter are performed. To verify the performance of the proposed converter a 100W converter has been designed

• 제어로봇시스템학회:학술대회논문집
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• 2004.08a
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• pp.2051-2054
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• 2004

This paper proposes a more accurate task level energy measurement technique for high speed microprocessors. The technique is based on the relationship of the amount of current consumed by the microprocessor and the pulse width of the power supply controller chip, employed in the synchronous buck DC-DC converter in the microprocessor's power supply. The accuracy of the measurement is accomplished by measuring variation in pulse width in each power supply cycle. The major advantage of this technique is that its accuracy does not depend on the operating frequency of the microprocessor. To prove the proposed technique, we implemented the measurement unit of the microprocessor energy meter using an FPGA chip operating at 50 MHz. Both static and dynamic load measurement are tested in order to obtain some behaviours. Moreover, various commercially available mainboards which employ synchronous buck regulators at 200 KHz switching frequency, were measured. The results agree with previous works with better accuracy at higher operating frequency.

• Proceedings of the KIPE Conference
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• 2004.11a
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• pp.71-75
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• 2004

In this paper, in order to develop a simple and high efficient ballast without an external igniter, a half-bridge type ballast with a coupled inductor and a frequency controlled synchronous rectifier is proposed. The internal LC resonance of the buck converter is used In generate a high voltage pulse for the ignition, and the coupled inductor filter is used for steady state ripple cancellation. Also, a synchronous buck converter is applied for the DC/DC converter stage. In order to improve the efficiency of the ballast, a frequency control method is proposed. This scheme reduces a circulation current and turn off loss of the MOSFET switch on the constant power operation, which results in increase of the efficiency of the ballast system about $4\%$, compared to a fixed frequency control. It consists a 2-stage version ballast with a PFC circuit. The results are verified with hardware experiments.

• Journal of Power Electronics
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• v.5 no.2
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• pp.104-108
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• 2005

This paper presents the performance improvement of voltage-mode controlled interleaved synchronous buck converters. This is a voltage-mode controlled scheme, where the controllers do not need an external saw-tooth generator for PWM generation and the loop design is easier. The controller implementation requires only a single error amplifier and gives almost current mode control performance. The control scheme uses voltage feedback with two loops similar to current mode control: one for the slow outer loop and the other for the faster inner PWM control loop. To improve the performance of the converter system a coupled inductor is used. This coupled inductor reduces the magnetic size and also improves the converter's transient performance without increasing the steady-state current ripple. The effectiveness of the proposed control scheme is demonstrated through PSIM simulations.

• Journal of Power Electronics
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• v.9 no.4
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• pp.517-525
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• 2009

42V electrical power systems are on their way to replacing the present l4V systems in automobiles and 42V/14V dual voltage systems have been proposed to provide backward compatibility with the existing components for the 14V systems. A synchronous buck/boost converter is an attractive topology for 42V/14V dual voltage systems since it offers the possibility of bi-directional operation without additional components. In this paper, transient currents generated during converter startup or changes in operation modes between buck and boost are analyzed and a cost effective solution to remove the transient currents is proposed. The validity of the proposed control strategy is investigated through simulation and experiment with bi-directional converters.