• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• v.5B no.4
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• pp.366-373
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• 2005

This paper presents two new circuit topologies of the dc busline side active resonant snubber assisted voltage source high frequency link soft switching PWM full-bridge dc-dc power converters acceptable for either utility ac 200V-rms or ac 400V-rms input grid. These high frequency switching dc-dc converters proposed in this paper are composed of a typical voltage source-fed full-bridge PWM inverter, high frequency transformer with center tap, high frequency diode rectifier with inductor input filter and dc busline side series switches with the aid of a dc busline parallel capacitive lossless snubber. All the active switches in the full-bridge arms as well as dc busline snubber can achieve ZCS turn-on and ZVS turn-off transition commutation with the aid of a transformer leakage inductive component and consequently the total switching power losses can be effectively reduced. So that, a high switching frequency operation of IGBTs in the voltage source full bridge inverter can be actually designed more than about 20 kHz. It is confirmed that the more the switching frequency of full-bridge soft switching inverter increases, the more soft switching PWM dc-dc converter with a high frequency transformer link has remarkable advantages for its power conversion efficiency and power density implementations as compared with the conventional hard switching PWM inverter type dc-dc power converter. The effectiveness of these new dc-dc power converter topologies can be proved to be more suitable for low voltage and large current dc-dc power supply as arc welding equipment from a practical point of view.

• Proceedings of the KIPE Conference
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• 2001.07a
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• pp.584-588
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• 2001

A conventional power supply to drive a microwave oven has ferro-resonant transformer and high voltage Capacitor(HVC). Though it is simple, transformer is bulky, heavy and has low-efficiency. To improve this defect a high frequency inverter type power supply has been investigated and developed in recent years. But, because of additional control circuit and switching device, inverter-type power supply is more expensive than conventional one. In this study, A new pulse power supply for Microwave Oven using novel HVC embedded high frequency transformer is proposed for down-sizing, cost reduction, and efficiency emprovement of Inverter type power supply. Also, equivalent circuit model is derived by impedance measurements. And the operation of proposed pulse power supply is verified by simulations and experimental results.

• The Transactions of the Korean Institute of Power Electronics
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• v.4 no.3
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• pp.231-239
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• 1999

An improved version of current-regulated delta modulator (CRDM) is investigated for the output cunent control of v voltage-source inverters that have transformer-coupled series resonant load and are operated at the resonant frequency. Conventional CRDM has not only CUlTent offset problem but also transformer flux saturation problem when i it is applied to induction heating systems that have transformel-coupled loads. To cope with these problems, the effect of flux saturation is analysed, and simple method to av이d the problem is proposed. And integral type of CRDM is a adopted to remove the cunent offset. The boundaries of integrator gain for stable operation is calculated using the c concept of sliding mode controL The validity of proposed strategy is vel퍼ed through simulations and prototype e experiments.

• The Transactions of the Korean Institute of Power Electronics
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• v.8 no.2
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• pp.180-191
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• 2003

In this paper, the modelings of PSPICE of the piezoelectric transformer and CCFL drive circuit using an electrical equivalent circuit is proposed. In the CCFL drive circuit modeling the model parameters of the CCFL were derived using the method of least squares because push-pull inverter and loads such as CCFL were also modeled using PSPICE. It is considered that the simulation techniques can be used in the piezoelectric devices such as piezoelectric transformer.

• 제어로봇시스템학회:학술대회논문집
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• 1996.10a
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• pp.255-258
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• 1996

This paper describes a DC voltage controller for the DC power supply which is constructed using the full-bridged MOS-FET DC-to-RF power inverter and rectifier. The full-bridged MOS-FET DC-to-RF inverter consisting of four MOSFET arrays and an output power transformer has a control function which is able to control the RF output power when the widths of the pulse voltages which are fed to four MOS-FET arrays of the fall-bridged inverter are changed using the pulse width control circuit. The power conversion efficiency of the full-bridged MOS-FET DC-to-RF power inverter was approximately 85 % when the duty cycles of the pulse voltages were changed from 30 % to 50 %. The RF output voltage from the full-bridged MOS-FET DC-to-RF inverter is fed to the rectifier circuit through the output transformer. The rectifier circuit consists of GaAs schottky diodes and filters, each of which is made of a coil and capacitors. The power conversion efficiency of the rectifier circuit was over 80 % when the duty cycles of the pulse voltages were changed from 30 % to 50 %. The output voltage of the rectifier circuit was changed from 34.7V to 37.6 V when the duty cycles of the pulse voltages were changed from 30 % to 50 %.

• Proceedings of the KIEE Conference
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• 2002.07b
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• pp.1348-1350
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• 2002

This paper describes an efficient comparison of the different factor both transformer and inductor. And also the 3 kW class inverter was fabricated for the analysis of the Photovoltaic(PV) power system's performance. The result of the performance of the 3 kW inverter showed that the total harmonics distortion(THD) was 3.19%, the conversion efficiency of the inverter was above 90 % at an over half load, respectively.

• Proceedings of the KIEE Conference
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• 2002.07b
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• pp.1199-1201
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• 2002

Today, the ceramic transformer becomes widely used for the TFT LCD backlight inverter system thanks to its high efficiency and small size. In this paper, a high efficient inverter system for cold cathode flourescent lamp (CCFL) including PLL controller for tuning the PWM frequency to the frequency that the efficiency of the inverter system becomes maximum is proposed. The control IC implementing this feature will be released by Interpion Co. Ltd. in May 2002.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.18 no.9
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• pp.982-989
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• 2008

There is a noticeable hum from the inverter board of LCD TV when in operation. In this study, we investigate the source and the characteristics of this noise for the inverter board of LCD TV using measurement of vibration and noise. Modal analysis of vibration and noise is visualized for identification of noise sources and transmission vibration. The main source of noise was the transformer of the LCD TV inverter. A noise reduction was achieved by damping the structural elements.

• Proceedings of the KIEE Conference
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• 1989.07a
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• pp.507-509
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• 1989

In multiple current source inverter, generally, transformer connection method and direct connection method in output side have been used. But these methods have faults such as the increment of the number of inverter and the need of the transformer for changing phase in order to get above 12 phase. In this system, we obtained the output currents of 24 phase by adding 2taps in 12 phase inverter. Therefore, this system has such characteristics as the miniaturization of devices and the simplicity of control signal by controlling two inverters and two SCRs for changing taps.

• Proceedings of the KIPE Conference
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• 2018.07a
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• pp.290-291
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• 2018

This paper proposed design method of DC link capasitor and leakage inductance of transformer with high voltage cascaded NPC H-bridge inverter. DC link capacitor is designed based on the ripple power between input AC power and output AC power, and leakage inductance of transformer is designed based on FFT table of unipola PWM with NPC H-bridge inverter. The proposed design method is verified by simulation results of 6.6[kV], 1.2[MW] Cascaded NPC H-bridge inverter.