Short Circuit Requirements of Power Converters based upon Wide-Bandgap -Author Pappis, DouglasThis work has been accepted by the Faculty of Electrical Engineering / Computer Science of the University of Kassel as a thesis for acquiring the academic degree of Doktor der Ingenieurwissenschaften (Dr.-Ing.).

 

ABSTRACT

In power electronics designs, the evaluation and prediction of potential fault conditions on semiconductors is essential for achieving safe operation and reliability, being short circuit (SC) one of the most probable and destructive among the failures. It can occur externally to the power converter by shortening the load, or internally due to failures on galvanic isolations, stress on passive components, or even in the power semiconductors themselves. Silicon (Si) based power semiconductors have been extensively investigated with regards to their SC capability, although there is still on-going research as their design is being pushed closer to theoretical limits. Recent improvements on Wide-Bandgap (WBG) semiconductors such as Silicon Carbide (SiC) and Gallium nitrite (GaN) enable power electronic designs with outstanding performance, reshaping the power electronics landscape. In comparison to Si, SiC and GaN power semiconductors physically present smaller chip areas, higher maximum internal electric fields, and higher current densities. Such characteristics yield a much faster rise of the devices internal temperatures, worsening their SC performance if compared to Si.

LINK: https://kobra.uni-kassel.de/bitstream/handle/123456789/13296/orig_9783737609777.pdf?sequence=2&isAllowed=y

Método de carga para banco de baterias em fontes ininterruptas de energia que busca garantir o estado de carga completa: corrente pulsada modificado--Cardoso, Renato Tavares (Universidade Federal de Santa Maria)

 

ABSTRACT

Esta dissertação de mestrado tem como proposta o desenvolvimento de um sistema de gerenciamento de carga de um banco de 16 baterias de chumbo ácido, com capacidade de carga de 7Ah, comumente utilizado em Fontes Ininterruptas de Energia (UPS). Este sistema visa garantir que estas baterias cheguem a um estado de carga completo e de forma mais rápida que a convencional. Para isto, foi escolhido fazer a modificação do método de carga de corrente pulsada, com o objetivo de reduzir problemas inerentes do método tomado como base, quando ocorre o intervalo de retirada de energia da bateria, tais como: elevação da tensão do barramento ao retornar a energia para ele, ou, dissipar esta energia em uma resistência, o que acarreta em baixa eficiência do sistema. Para o desenvolvimento do sistema de carga sugerido foi escolhido o conversor estático Full-Bridge Isolado com modulação Phase Shift. Foi feita a modelagem simplificada deste conversor, para a implementação do controle digital, assim como o desenvolvimento prático do mesmo em laboratório. São apresentados os resultados de simulação e experimentais para validar o método. 

 LINK: https://repositorio.ufsm.br/bitstream/handle/1/8576/CARDOSO%2c%20RENATO%20TAVARES.pdf?sequence=1&isAllowed=y

High-voltage power supply for x-ray computed tomography and time-delay compensation of cockcroft-walton circuit Yuki Kajiuchi and Toshihiko Noguchi Canon Medical Systems Corporation, Tochigi, Japan. Department of Engineering, Graduate School of Integrated Science and Technology, Shizuoka University, Hamamatsu, Japan

 

High-voltage power supply for x-ray computed tomography and time-delay compensation of cockcroft-walton circuit Yuki Kajiuchi and Toshihiko Noguchi Canon Medical Systems Corporation, Tochigi, Japan. 2Department of Engineering, Graduate School of Integrated Science and Technology, Shizuoka University, Hamamatsu, Japan. 

Abstract.

 In recent years, an image diagnostic apparatus using X-ray is intensively investigated to reduce the radiation exposures amount. Above all, high-speed control of the high voltage generator to control the X-ray output is a very important issue. A Cockcroft-Walton circuit (CW circuit) is one of the method to generate the high voltage output. However, it has problem of the long time delay in the output response due to the huge capacitive component of the CW circuit. Therefore, it is required to achieve the stable output voltage with a quick transient response, which can be obtained by the time delay compensation technique of the CW circuit. This paper proposes an application of a Smith method to compensate for the time delay of the CW circuit output to reduce the undesirable excessive radiation exposure. AS a result of verification through the computer simulation, it has been confirmed that the overshoot of the output voltage can effectively be suppressed and that the optimal response can be realized without sacrificing the high-speed response. The paper indicates some possibilities of further improvement of the CW circuit output response by introducing the more precise compensation technique to the X-ray computed tomography. 

LINK:https://www.researchgate.net/publication/337182375_High-voltage_power_supply_for_x-ray_computed_tomography_and_time-delay_compensation_of_cockcroft-walton_circuit

변압기 없는 고승압 직류 컨버터용 대칭형 Cockcroft-Walton 회로 (Symmetrical Cockcroft-Walton circuit for Transformerless High Step-Up DC-DC Converter) 차대중*․백지은․고광철** (Dae-Joong Cha․Ji-Eun Baek․Kwang-Cheol Ko)-Journal of the Korean Institute of IIIuminating and Electrical Installation Engineers (2015--

 

변압기 없는 고승압 직류 컨버터용 대칭형 Cockcroft-Walton 회로 (Symmetrical Cockcroft-Walton circuit for Transformerless High Step-Up DC-DC Converter) 차대중*․백지은․고광철** (Dae-Joong Cha․Ji-Eun Baek․Kwang-Cheol Ko) 

Abstract 

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.

LINK VIEW FULL TEXT: https://www.koreascience.or.kr/article/JAKO201505041841025.pdf

Cockcroft-Walton Voltage Multiplier Simulation According to Diode Parasitic Capacitance for Xray Generator Designing Xray 발생장치 설계를 위한 다이오드 기생 커패시턴스에 따른 Cockcroft-Walton Voltage Multiplier 시뮬레이션 Im, Gyu-Wan (KONKUK University) ; Mok, Hyung-Soo (KONKUK University) ; Zhu, He-Lin (KONKUK University) 임규완 (건국대학교) ; 목형수 (건국대학교) ; 주학림 (건국대학교)

 ABSTRACT

Due to the recent outbreak of COVID-19 (Coronavirus disease, 2019), The demand for X-ray examinations to make a definitive diagnosis is increasing. In order to obtain high-quality Xray images, the X-ray tube A constant high voltage suitable for the purpose of shooting must be applied to the camera through control. To do this, consider the output voltage characteristics of the power converter. should be designed Therefore, it is mainly used for Xray generators. of the diode using the Cockcroft-Walton Voltage Multiplier. The parasitic capacitance component is the leakage inductance component of the transformer, and the The parasitic inductance component and the output voltage generated by resonance.

LINK VIEW FULL TEXT: https://www.koreascience.or.kr/article/CFKO202026958570456.pdf