• The Transactions of the Korean Institute of Power Electronics
• /
• v.18 no.1
• /
• pp.72-83
• /
• 2013

The paper proposes a new multilevel variable output voltage AC/DC Converter for power supply of power amplifiers used in underwater acoustic sensors. The proposed multilevel variable output voltage AC/DC Converter is composed of two parts. One as the input section is the high efficiency phase-shifted PWM full bridge DC-DC converter to get multiport power sources. The other as the output section is composed of two flying-capacitor 3-level DC-DC converters and a diode bridge circuit to get fast-response and multilevel variable output voltage for an envelope amplifier. Also the paper suggests the detailed circuit topology and design guideline of multilevel variable output voltage AC/DC converter. It also proposes the power balanced control method between 3-level converters and the voltage balanced algorithm for flying capacitors. Its characteristics should be verified by the detailed simulation results. It is anticipated that the proposed converter will be used very well for power amplifiers used in underwater acoustic sensors.

• Journal of Electrical Engineering and Technology
• /
• v.1 no.3
• /
• pp.332-337
• /
• 2006

In this paper, an electronic ballast was developed to control a 250W metal halide lamp. To avoid acoustic resonance phenomenon, we calculated the acoustic resonance band and determined the driving frequency from 70kHz to 100kHz. Due to the switching loss of MOSFET, many problems are caused in the inverter circuit during lamp lighting, so we reduced the loss by connecting the capacitor that minimizes the magnitude of the impulsive voltage. In this paper, the main point of research is to find the methods to operate the lamp on the rated output power. After detecting the current and the voltage of the lamp, we changed the driving frequency by adjusting the DC voltage level of the VCO input.

• Proceedings of the KIEE Conference
• /
• 1991.07a
• /
• pp.596-599
• /
• 1991

This paper describes a novel switching algorithm of series connected power semiconductors for high voltage applications. In order to improve the reliability and efficiency of high voltage static power converters, we study on the switching characteristics of series connected power semiconductors and then propose "a servo control of snubber capacitor value" for the dynamic voltage balancing under turn-off state in series connected power semiconductors. Finally, we illustrate the validity of this algorithm by computer simulation and experimental results.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.63 no.7
• /
• pp.924-928
• /
• 2014

LLC resonant converter is used to control laser power density in ruby laser power supply. Zero voltage switching(ZVS) is implemented to minimize the switching loss by the LLC resonant converter. Laser output power is investigated and experimented by changing the output current. That current is controled by the charging voltage of capacitor. From those results, we obtained the maximum laser output of 1.94J at the discharge current of 860A and the pulse repetition rate of 1Hz.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.6 no.3
• /
• pp.265-272
• /
• 2001

The traditional 60[Hz] power supply for during magnetron in microwave oven has disadvantages of heavy weight and low efficiency due to 60[Hz] High Voltage Transformer(HVT), capacitor and th phase control of thyristors. To alleviate these disadvantages, this paper proposes a 20[kHz] phase-shifted Full-Bridge(FB) Zero-Voltage-Switched(ZVS) PWM converter for driving a 600[W] magnetron in an 1[kW] microwave oven. The proposed converter has advantages of light weight and high power density.

• Journal of Information Display
• /
• v.9 no.2
• /
• pp.1-4
• /
• 2008

In this study, we investigate the capacitance-voltage (C-V) characteristics of metal-insulator-semiconductor (MIS) capacitors consisting of pentacene, as an organic semiconductor, and polymeric insulators such as poly(4-vinylphenol) (PVP) orpolystyrene (PS) prepared by spin-coating process, to analyze the interfacial characteristics between pentacene and polymeric insulators. Compared with the device with PS, the MIS capacitor with PVP exhibited a pronounced shift in the flat-band voltage according to the bias sweep direction. This hysteric feature in the C-V characteristics is thought to be attributed to the trapped charges at the interface between pentacene and PVP owing to the hydrophilicity of PVP. From the experimental results, we can conclude that surface polarity of polymeric insulator has a critical effect on the interfacial properties, thereby affecting the bias stability of organic thin-film transistors.

• 한국정보디스플레이학회:학술대회논문집
• /
• 2005.07b
• /
• pp.898-901
• /
• 2005

We propose a novel pixel structure using bootstrapped voltage programming for amorphoussilicon TFT backplane of AM-OLED (Active Matrix-Organic Light Emitting Diode) displays. The proposed structure is composed of two TFTs and one capacitor. It operates at low drive voltage ($0{\sim}5V$) which can reduce power consumption comparing with the conventional pixel circuit structure using same OLED material. Also, it can easily control dark level and use commercial mobile LCD ICs. In this paper, we describe the operating principle and the characteristics of the proposed pixel structure and verify the performance by SPICE simulation comparing with the conventional pixel structure.

• The Transactions of the Korean Institute of Electrical Engineers P
• /
• v.54 no.4
• /
• pp.179-184
• /
• 2005

This paper examines the application of high voltage static var compensator(SVC) with cascade multilevel inverter which employs H-bridge inverter(HBI). A new switching scheme is developed for the SVC system. To improve the unbalanced problem of the DC capacitor voltages, the rotated switching scheme of fundamental frequency is newly used. The optimized fundamental switching pattern with low switching frequency is adapted to be suitable for high application. The selective harmonic elimination method(SHEM) allows to keep the total harmonic distortion(THD) low in the output voltage of multilevel inverter. The SVC system is modeled using the d-q transform which calculates the instantaneous reactive power. This model is used to design a controller and analyze the SVC system. Simulated and experimental results are also presented and discussed to validate the proposed schemes.

• 제어로봇시스템학회:학술대회논문집
• /
• 1990.10b
• /
• pp.1420-1423
• /
• 1990

DC series motor has been widely applicated in industry due to many advantageous characteristics, such as high starting torque, easy construction of its controller, and cost economy, etc.. However, by high starting current, excessive surge voltage, and so on, many problems which could make engineers relinguish to use it are induced. In this paper, various protection methods for power circuit are discussed. Particularly, a new proposed snubber circuit which consists of two diodes, one capacitor, and a resistor increases the performance with respect to the suppression of the surge voltage. Furthermore, the plugging algorithm, by checking the armature current and voltage and controlling the field coil current, is designed and implemented. Also, these methods and algorithms were applicated in electric vehicle, and we could find its stability to be considerably improved.

• Proceedings of the KIPE Conference
• /
• 2006.06a
• /
• pp.366-368
• /
• 2006

The conventional 3-Level LLC Converter using frequency-control has a disadvantage of designing magnetic components. To overcome this problem, a new constant frequency phase-shift controlled three-level LLC converter is proposed. Moreover, by employing voltage doubler type rectifier, an additional resonant capacitor is not needed. Therefore, this converter is promising for the high-power, high-voltage application with simple structure.