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RISS 인기검색어
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- 저자 : Zhang Fanghua (검색결과 6 건)
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A study on stray capacitance of ferrite Common Mode Chokes for EMI filters
Guangdong Dong,Fanghua Zhang 전력전자학회 2019 ICPE(ISPE)논문집 Vol.2019 No.5
The stray capacitance of CM chokes consists of the material capacitance and the winding parasitic capacitances. The material capacitance is determined by the intrinsic material properties of the ferrite core. The influence of ferrite core material on stray capacitance of CM chokes are researched. The complex magnetic permeability (CMP) of a ferrite core is measured and the CMP characteristic is analyzed. The behavior of the material capacitance is inversely proportional to the square of turn N. Winding parasitic capacitances include turn-to-turn capacitance and turn-to-core capacitance. An analytical method is adopted to calculate the winding parasitic capacitances taking into the core physical construction and material properties. Based on the capacitance network model, the stray capacitance can be derived. The impedance characteristic of a CM choke is tested using impedance analyzer to extract the stray capacitance, and the analytical result is consistent with the measured result.
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Modeling and Analysis of a Buck/Boost Bidirectional Converter with Developed PWM Switch Model
Wang Jianhua,Zhang Fanghua,Gong Chunying,Chen Ran 전력전자학회 2011 ICPE(ISPE)논문집 Vol.2011 No.5
The aim of this paper is to provide a general method for bidirectional converter simulation and evaluation. A developed PWM switch model is proposed for bidirectional power flow application. A typical buck/boost bidirectional converter is chosen as a test bench for evaluation. Small signal analysis results show mode transition between battery charging and discharging modes. It provides a fast simulation tool to investigate steady and transient response of converters. The accuracy of the modeling technique is verified by a detailed comparison of simulated results with the developed PWM switch model and component circuit.
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Dong, Guangdong,Zhang, Fanghua The Korean Institute of Power Electronics 2019 JOURNAL OF POWER ELECTRONICS Vol.19 No.5
Common mode (CM) chokes are a crucial part in EMI filters for mitigating the electromagnetic interference (EMI) of switched-mode power supplies (SMPS) and for meeting electromagnetic compatibility standards. However, the parasitic capacitances of a CM choke deteriorate its high frequency filtering performance, which results in increases in the design cycle and cost of EMI filters. Therefore, this paper introduces a negative capacitance generated by a negative impedance converter (NIC) to cancel the influence of equivalent parallel capacitance (EPC). In this paper, based on a CM choke equivalent circuit, the EPCs of CM choke windings are accurately calculated by measuring their impedance. The negative capacitance is designed quantitatively and the EPC cancellation mechanisms are analyzed. The impedance of the CM choke in parallel with negative capacitances is tested and compared with the original CM choke using an impedance analyzer. Moreover, a CL type CM filter is added to a fabricated NIC prototype, and the insertion loss of the prototype is measured to verify the cancellation effect. The prototype is applied to a power converter to test the CM conducted noise. Both small signal and EMI measurement results show that the proposed technique can effectively cancel the EPCs and improve the CM filter's high frequency filtering performance.
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Guangdong Dong,Fanghua Zhang 전력전자학회 2019 JOURNAL OF POWER ELECTRONICS Vol.19 No.5
Common mode (CM) chokes are a crucial part in EMI filters for mitigating the electromagnetic interference (EMI) of switched-mode power supplies (SMPS) and for meeting electromagnetic compatibility standards. However, the parasiticcapacitances of a CM choke deteriorate its high frequency filtering performance, which results in increases in the design cycle and cost of EMI filters. Therefore, this paper introduces a negative capacitance generated by a negative impedance converter (NIC) to cancel the influence of equivalent parallel capacitance (EPC). In this paper, based on a CM choke equivalent circuit, the EPCs of CM choke windings are accurately calculated by measuring their impedance. The negative capacitance is designed quantitatively and the EPC cancellation mechanisms are analyzed. The impedance of the CM choke in parallel with negative capacitances is tested and compared with the original CM choke using an impedance analyzer. Moreover, a CL type CM filter is added to a fabricated NIC prototype, and the insertion loss of the prototype is measured to verify the cancellation effect. The prototype is applied to a power converter to test the CM conducted noise. Both small signal and EMI measurement results show that the proposed technique can effectively cancel the EPCs and improve the CM filter's high frequency filtering performance.
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Yonghong Peng,Shuai Zhang,Fanghua Zhu,Wa Li,Yong Yi,Kai Du,Qiang Yin 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2018 NANO Vol.13 No.7
There is a demand for composite films with excellent hydrophobic properties in inertial confinement fusion (ICF) physics experiments. In this paper, we prepared fluorinated polyimide hydrophobic films using spinning and plasma etching methods. The experimental results indicate that the water contact angle for the perfluorodecyltrichlorosilane (PFTS) treatment polyimide (PI) film is 112.0°, which is larger than the pure PI film (69°). The rap oil contact angle is 84.2°, which is also much larger than the contact angle of PI film (12°). Moreover, the surface roughness of the prepared films was measured by white light interferometry (WLI). The surface roughness (Ra) of pure PI is 9.79 nm, but with the application of FSiO2 particles, the Ra of the films increases to 65.05 nm. After plasma treatment, the Ra of the PI/FSiO2 composite film increases to 186.71 nm because plasma treatment can scratch the film surface and increase its roughness. However, treating the PI/FSiO2 composite film with the plasma and PFTS, the Ra is only 88.90 nm. This decrease in Ra is due to the PFTS, which is able to reduce the surface roughness. The development of composite films, compared to pure PI films, could prove to be an extremely valuable material in ICF experiments.
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Synthesis and Characterization of Poly(N-arylenebenzimidazole ketone ketone)s
Yewei Xu,Jie Tang,Guanjun Chang,Fanghua Zhu,Xuan Luo,Lin Zhang 한국고분자학회 2013 Macromolecular Research Vol.21 No.6
Poly(N-arylenebenzimidazole ketone ketone)s (PNABIKKs) consisting of m- and p-phenylene linkages have been synthesized by nucleophilic aromatic substitution from bis(benzimidazolyl) derivatives containing sulfonyl,carbonyl, and ether groups with activated aromatic difluorides in sulfolane at 210 oC in the presence of anhydrous potassium carbonate. The structures of the polymers were characterized by means of Fourier tramsfom infrared (FTIR), proton nuclear magnetic resonance (1H NMR) spectroscopy, and elemental analysis, and the results were largely consistent with the proposed structure. Differential scanning calorimetry (DSC) and thermogravimetric analysis (TG) measurements demonstrated that polymers had high glass transition temperatures (Tg>220 oC) and good thermal stability with high decomposition temperatures (TD>480 oC). These novel polymers also showed good solubility.
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