• Proceedings of the KIPE Conference
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• 1999.07a
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• pp.585-590
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• 1999

The conventional $CO_2$ inverter arc machine has constant voltage output characteristic and uses constant wire speed controller for welding current control. By adoption of PWM inverter to the welding machine, the spattering was reduced rather than the thyrister arc welding machine or AC arc welding machine. Moreover, by the high switching frequency, the output reactor size could be reduced evidently. Recently, the studies on optimal voltage and current waveform for the welding performance improvement have been studied. In this paper, a new instantaneous output current control scheme during the short circuit mode was proposed and showed the capability of arc stability improvement and the reduction of spatter generation.

• Proceedings of the KIPE Conference
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• 1998.10a
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• pp.524-528
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• 1998

The voltage-source inverters are normally equipped with an electrolytic capacitor in their DC link, however, the electrolytic capacitor has several disadvantages such as increasing size, limiting converter life and reliability. Therefore, several approaches for removing the DC link capacitor have been studied by the authors. This paper proposes a new voltage-source inverter without DC link components. To reduce waveform distortion of the AC source current, the current-controlled PWM-rectifier with di/dt feedback is introduced. The di/dt feedback gain and LC parameters are investigated by calculation for a 0.75kW induction motor driven by this inverter. The calculated AC source currents maintain nearly sinusoidal waveforms with a unity power factor.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.51 no.11
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• pp.628-634
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• 2002

A capacitor-charging power supply using high frequency inverter technology is strongly recommended for the charging section of the pulsed power supplies. A high frequency inverter swiching makes the overall system size small. The command-charging feature can guarantee the higher reliability of switching function. The protection circuit can be easily included in the system and the good regulation of charging voltage can be acieved by the feedback system. Several modules can be stacked to supply required output power and a failed module can be easily replaced. A 50-kV, 35-kW capacitor charging power supply is developed. In this paper the detailed design and test results of a prototype unit are presented.

• Journal of Information Display
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• v.6 no.4
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• pp.11-15
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• 2005

We propose a current mode logic circuit design method for LTPS TFT for enhancing circuit operating speed. Current mode inverter/buffers with passive resistive load had been designed and fabricated. Measurement results indicated that the smaller logic swing of the current mode allowed significantly faster operation than the static CMOS. In order to reduce the chip size, both all pTFT and all nTFT active load current mode inverter/buffer had been designed and analyzed by HSPICE simulation. Even though the active load current mode circuits were inferior to the passive load circuits, it was superior to static CMOS gates.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.52 no.1
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• pp.33-38
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• 2003

This paper describes control principles of the piezoelectric ultrasonic motor which is operated by the ultrasonic vibration generated by the piezoelectric element. The piezoelectric ultrasonic motor has excellent characteristics such as compact size, noiseless motion, low speed, high torque and controllability, and has been recently applied for the practical utilization in industrial, consumer, medical and automotive fields. In this paper, the design of two-phase push-pull inverter for driving the piezoelectric ultrasonic motor is described, and a new control method of automatic resonant frequency tracking using PLL(Phase-Locked Loop) technique is mainly presented. the experimental results by this inverter system for driving the piezoelectric ultrasonic motor are illustrated herein. The inverter system with PLL technique improved the speed stability of the piezoelectric ultrasonic motor.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.5
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• pp.976-981
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• 2009

This paper proposed optimal design and microcontroller driver for driving the thin-type ultrasonic motor. To find the optimal size of the stator, motions of the motor were simulated using ATILA by changing length, width and thickness of the ceramics. Two sinusoidal waves which have 90 degree phase difference were needed for driving the thin-type motor. The thin-type ultrasonic motor driver was composed of microcontroller(Atmega128), push-pull inverter, encoder and AD-converter. Microcontroller generates four square waves which have variable frequency and 25[%] duty ratio in $20{\sim}150$[kHz]. The output signals of microcontroller were converted to sine wave and cosine wave by push-pull inverter and were applied to the thin-type ultrasonic motor. The encoder and AD-converter were used for maintaining speed of the thin-type ultrasonic motor. The AD-converter controlled DC voltage of inverter in accordance with output signal of encoder. Using the driver, characteristics of the motor as speed and torque were measured.

• Journal of Power Electronics
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• v.13 no.6
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• pp.919-927
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• 2013

This paper proposes a Boundary Current Mode (BCM) control scheme to realize soft switching on a conventional single phase full bridge DC/AC inverter. This technique with the advantages of no auxiliary components, low cost, high efficiency, and simple in control, is attractive for micro-inverter applications. The operation principle and characteristic waveforms of the proposed soft switching technique are analyzed in theory. A digital controller is provided based on that theory. To balance the requirements of efficiency, switching frequency, and inductor size, the design considerations are discussed in detail to guide in BCM inverter construction. A 150W prototype is built under these guidelines to implement the BCM control scheme. Simulation and experiment results demonstrate the feasibilities of the proposed soft switching technique.

• Proceedings of the KIPE Conference
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• 2001.10a
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• pp.146-150
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• 2001

A new three-phase soft-switching active front-end inverter is presented. The topology consists of a quasi-resonant PWM boost converter with an additional resonant branch, which provides low loss at high frequency operation. This leads to a high conversion efficiency and a remarkable reduction in the size of the input inductor. To synchronise the PWM pattern with the resonance cycle, a modified space vector modulation with asymmetrical PWM pattern is used. A high power factor can be achieved for both power flow directions. Due to a new control strategy the converter features a low content of harmonics in the line currents even for distorted line voltages.

• Proceedings of the KIPE Conference
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• 2020.08a
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• pp.205-208
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• 2020

This paper examines the approach, enabled by using SiC power devices, to unify the inverter design for central air conditioning (CAC) system for both single- and 3-phase input, and reduce the PFC inductor size to be PCB-mountable. By using SiC-instead of Si-diode in PFC stage, it is possible to increase the switching frequency from 16kHz to 60kHz to reduce the required PFC inductance from 0.93mH to 0.25mH, thus enable PCB-mounting of inductor. With the next step of using 1200V SiC MOSFET instead of Si-IGBT, the DC link voltage can be boosted from 311Vdc to 550Vdc in PFC stage, allowing the inverter and compressor used in 3-phase input CAC be used for single-phase input as well. Furthermore, using SiC MOSFET in inverter stage can further reduce total loss system total loss to 200.8 W. Simulation and experimental results are presented in the paper.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.4
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• pp.2320-2323
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• 2014

Piezoelectric inverter for driving CCFL is designed in this study. Of them, CCFL is generally used because it has advantages such as small size, high efficiency and good brightness characteristics. the description of the piezoelectric effect is not present here and can be easily found in numerous publications as well as complex equations and formulae. What is the most important to understand is that "they are different" one cannot just change an electromagnetic transformer(EMT) for a piezoelectric one. The simulation program supports the modeled piezoelectric inverter for this paper and the equivalent circuit. The result of the experiment shows more than 90% improvement in terms of the efficiency.