• 조명전기설비학회논문지
• /
• 제29권8호
• /
• pp.70-75
• /
• 2015

High Step-up DC-DC Converters have been demanded for renewable energy applications. Transformer or coupled inductor is generally used to boost output voltage of converters. This methods can relatively obtain high voltage than others, whereas have heavy weight and high cost. To complement these disadvantages, we studied transformerless high step-up DC-DC converter. In various transformerless topologies, Boost converters combined with Cockcroft-Walton have studied. In this paper, we proposed a symmetrical Cockcroft-Walton circuit for transformerless high step-up DC-DC converter. Finally, we simulated proposed converter to compare with existing converter. As a result, proposed converter has higher duty ratio or lower cost than existing transformerless converters which are discussed in this paper.

• 전력전자학회:학술대회논문집
• /
• 전력전자학회 2020년도 전력전자학술대회
• /
• pp.397-398
• /
• 2020

최근 COVID-19(Coronavirus disease, 2019)의 발병으로 정확한 진단을 하기위한 X-ray 검사에 대한 수요가 증가하고 있다. 품질이 높은 수준의 Xray 영상을 얻기 위해서는 X-ray 튜브에 촬영 목적에 맞는 일정한 고전압을 제어를 통해 인가해야 한다. 그러기 위해서는 전력변환장치의 출력전압 특성을 고려하여 설계해야 한다. 따라서 Xray 발생장치에 주로 사용되는 Cockcroft-Walton Voltage Multiplier를 사용하여 다이오드의 기생커패시턴스 성분이 변압기의 누설 인덕턴스 성분, 회로의 기생 인덕턴스 성분과 공진현상을 일으켜 발생하는 출력전압의 특성 변화에 대한 시뮬레이션을 개발하고 분석 하였다.

• Journal of Electrical Engineering and Technology
• /
• 제6권6호
• /
• pp.842-848
• /
• 2011

The current study proposes the design of a hybrid series-parallel resonant converter (SPRC) and a three-stage Cockcroft-Walton voltage multiplier for precisely adjusting the power generated by a continuous wave (CW) $CO_2$ laser. The design of a hybrid SPRC, called LCC resonant converter, is described, and the fundamental approximation of a high-voltage and high-frequency (HVHF) transformer with a resonant tank is discussed. The results of the current study show that the voltage drop and ripple of a three-stage Cockcroft-Walton voltage multiplier depend on frequency. The power generated by a CW $CO_2$ laser can be precisely adjusted by a variable-frequency controller using a DSP (TMS320F2812) microprocessor. The proposed LCC converter could be used to obtain a maximum laser output power of 23 W. Moreover, it could precisely adjust the laser output power within 4.3 to 23 W at an operating frequency range of 187.5 to 370 kHz. The maximum efficiency of the $CO_2$ laser system is approximately 16.5%, and the minimum ripple of output voltage is about 1.62%.

• 전기전자학회논문지
• /
• 제14권2호
• /
• pp.9-15
• /
• 2010

In this study, we have been proposed the new type of a transcranial magnetic stimulation adopted a variable voltage capacitor with Cockcroft-Walton circuit and constant-frequency current resonant half-bridge inverter. This a transcranial magnetic stimulation has some merits compared with the conventional one. First, it doesn't require the high voltage transformer. And second, it has less switching losses, compact size and capability in adjusting the transcranial magnetic stimulation output energy precisely. In this paper, we have performed the output characteristics of a transcranial magnetic stimulation system which is well known as magnetic stimulation. The tested results are described as a function of pulse repetition rate and switching numbers of the half-bridge inverter.

• Journal of Electrical Engineering and Technology
• /
• 제12권4호
• /
• pp.1484-1494
• /
• 2017

We present a two-stage inverter with high step-up conversion ratio engaging modified finite-set Model Predictive Control (MPC) for utility-integrated photovoltaic (PV) applications. The anticipated arrangement is fit for low power PV uses, the calculated efficiency at 150 W input power and 19 times boosting ratio was around 94%. The suggested high-gain dc-dc converter based on Cockcroft-Walton multiplier constitutes the first-stage of the offered structure, due to its high step-up ability. It can boost the input voltage up to 20 times. The 3S current-source inverter constitutes the second-stage. The 3S current-source inverter hires three semiconductor switches, in which one is functioning at high-frequency and the others are operating at fundamental-frequency. The high-switching pulses are varied in the procedure of unidirectional sine-wave to engender a current coordinated with the utility-voltage. The unidirectional current is shaped into alternating current by the synchronized push-pull configuration. The MPC process are intended to control the scheme and achieve the subsequent tasks, take out the Maximum Power (MP) from the PV, step-up the PV voltage, and introduces low current with low Total Harmonic Distortion (THD) and with unity power factor with the grid voltage.

• 한국콘텐츠학회논문지
• /
• 제10권4호
• /
• pp.257-264
• /
• 2010

기존의 경두개 자극장치는 일정한 자극치료 펄스의 정현파 모양으로 다양한 치료 및 진단을 하는데 한계가 있다. 본 연구에서, 치료 및 진단마다 요구되는 세기, 폭, 펄스모양이 다른 코로로프트-월톤회로와 반파브리지 공진 인버터를 도입하여 주파수와 전압이 가변되는 새로운 장치를 제안하고자 한다. 기존장치 보다 많은 장점을 가진다. 첫째로 고압 변압기를 가지지 않는다. 둘째로 스위칭손실이 적고, 출력에너지를 정밀하게 제어할 수가 있다. 세째로 자극의 세기, 폭, 펄스모양이 다양하다. 결과적으로 변압기를 사용하지 않는 반파브리지 인버터와 코크로프트-월톤회로를 적용하여 개선된 특성과 실험을 구하였다.

• KIEE International Transactions on Electrophysics and Applications
• /
• 제3C권4호
• /
• pp.123-129
• /
• 2003

We propose a high voltage dc-dc converter for a CW (continuous wave) $CO_2$ laser system using a current resonant half-bridge inverter and a Cockcroft-Walton circuit. This high voltage power supply includes a 2-stage voltage multiplier driven by a regulated half-bridge series resonant inverter. The inverter drives a step-up transformer and the secondary transformer is applied to the voltage multiplier. It is highly efficient because of the reduced amount of switching losses by virtue of the current resonant half-bridge inverter, and also due to the small size, low parasitic capacitance in the transformer stage owing to the low number of winding turns of the step up secondary transformer combined with the Cockroft-Walton circuit. We obtained a maximum laser output power of 44 W and a maximum system efficiency of over 16%.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2003년도 하계학술대회 논문집 C
• /
• pp.1821-1823
• /
• 2003

We propose a high voltage dc-dc converter for CW(continuous wave) $CO_2$ laser system using a current resonant half-bridge inverter and a Cockcroft-Walton circuit. This high voltage power supply includes a 2-stage voltage multiplier driven by a regulated half-bridge series resonant inverter. The inverter drives a step-up transformer and the transformer secondary is applied to the voltage multiplier. Thus, it has high efficiency because of the less switching losses by virtue of the current resonant half-bridge inverter, and also compact size, small parasitic capacitance in the transformer stage owing to the low number of a winding turn of the step up transformer secondary by combining with Cockroft-Walton circuit. We could be obtained the maximum laser output power of 44 W and the maximum system efficiency of over 16 %.

• Applied Microscopy
• /
• 제34권1호
• /
• pp.51-59
• /
• 2004

주사전자현미경(SEM)에서 전자를 발생시키는 전자총 부분의 고압발생 장치를 설계 제작하고 그 안정성을 시험하였다. 고전압을 발생시키는 switching 주파수는 고압트랜스의 1차 측 임피던스와 인덕턴스에 matching 되는 주파수에서 최적의 전압 안정도가 유지되었다. 1차 측의 고압트랜스의 turn 수가 적으면 인덕턴스가 낮으므로 최적적인 matched switching 주파수가 높은 쪽으로 올라간다. 최대 출력 전압은 -30 kV 이상 출력되었으나 안정도는 출력전압이 -5 kV에서 10 kV 범위에서 가장 좋게 나타났다. 23.8 kHz에서 출력파형의 흔들림 없었고 DC 고전압 출력 또한 최고의 안정도을 보였다. 이때 도출된 전압 안정도는 ${\pm}0.002%$였다.

• 전기학회논문지
• /
• 제62권6호
• /
• pp.798-802
• /
• 2013

In a conventional DC power supply used for CO2 laser, the circuit elements such as a rectifier bridge, a current-limiting resistor, a high voltage switch, energy storage capacitors ans a high-voltage isolation transformer using high turn ratio are necessary. Consequently, those supplies are expensive and require a large space. Thus, laser resonator and power supply should be optimally designed. In this paper, we propose a new power supply using high frequency resonance phenomena for CW(Continuous wave) CO2 laser (maximum output of 23W with discharge length of 450mm). It consists of a transformer including leakage inductance, magnetizing inductance and half-bridge converter, a three-stage Cockcroft-Walton and PFC(Power factor correction) circuit. The output ripple voltage can be controlled the minimum of 0.24% under the high frequency switching of 231kHz. Furthermore, the output efficiency was improved to 16.4% and the laser output stability of about 5.6% was obtained in this laser system.