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A Novel Quasi-Resonant Snubber-Assisted ZCS-PWM DC-DC Converter with High Frequency Link
Khairy Fathy,Soon-Kurl Kwon 전력전자학회 2007 JOURNAL OF POWER ELECTRONICS Vol.7 No.2
In this paper, a novel type of auxiliary switched capacitor assisted edge resonant soft switching PWM resonant DC-DC converter with two simple auxiliary commutation lossless inductor snubbers is presented. The operation principle of this converter is described using the switching mode equivalent circuits. This newly developed multi resonant DC-DC converter can regulate its DC output AC power under a principle of constant frequency edge-resonant soft switching commutation by an asymmetrical PWM duty cycle control scheme. The high frequency power regulation and actual power characteristics of the proposed soft switching PWM resonant DC-DC converter are evaluated and discussed. The operating performances of the newly proposed soft switching inverter are represented based on simulation results from an applications point of view.
DC-DC Converter with Three-Phase Power Factor Correction for Arc Welder
Khairy Sayed,Keiki Morimoto,Soon-Kurl Kwon,Katsumi Nishida,Mutsuo Nakaoka 전력전자학회 2011 ICPE(ISPE)논문집 Vol.2011 No.5
This paper presents a PWM converter, which enables to maintain high power-factor of arc welding power supply and to suppress input current harmonics. The main function of this system is to maintain unity power-factor by controlling input current to be sinusoidal, and to generate stable DC output voltage through half-bridge inverter and output rectifier. The proposed converter has high power factor, low harmonic distortion, and tight output regulations. A control scheme is employed to reduce the switching and rectification losses. The modeling and simulation analysis are performed to evaluate the performance characteristics. The proposed converter meets the IEC 61000-3-2 regulations with near-unity power factor and high efficiency.
Khairy Fathy,Kang Hoon Koh,Hyun Woo Lee,Kwang - Joo Choi,Mutsuo Nakaoka 전력전자학회 2005 전력전자학술대회 논문집 Vol.- No.-
This paper presents two new circuit topologies of DC busline side active edge resonant snubber assisted soft-switching PWM full-bridge DC-DC converter acceptable for either utility AC 200V-rms or AC 400V-rms input voltage source. All the active power switches in the full-bridge arms and DC busline can achieve ZCS turn-on and ZVS turn-off commutations and the total turn-off switching power losses of all active switches can be reduced for high-frequency switching action. The effectiveness of these new DC-DC converters topologies is proved for low voltage and large current high efficiency DC-DC power supplies as TIG arc welding machine from a practical point of view.
A Novel Quasi-Resonant Snubber Assisted ZCS-PWM Soft-Switching DC-DC Converter
Khairy Fathy,Hyun Woo Lee,Mutsuo Nakaoka 전력전자학회 2006 전력전자학술대회 논문집 Vol.- No.-
In this paper, a novel type of auxiliary switched capacitor assisted edge resonant soft switching PWM resonant DC-DC Converter with two simple auxiliary commutation lossless inductor snubbers. The operation principle of this converter is described using the switching mode equivalent circuits. This newly developed multi resonant DC-DC Converter can regulate its dc output AC power under a principle of constant frequency edge-resonant soft switching commutation by asymmetrical PWM duty cycle control scheme. The high frequency power regulation and actual power characteristics of the proposed soft switching PWM resonant DC-DC Converter are evaluated and discussed. The operating performances of the newly proposed soft switching inverter are represented based on simulation a results from an application point of view.
Serum miRNA Panel in Egyptian Patients with Chronic Hepatitis C Related Hepatocellular Carcinoma
Khairy, Ahmed,Hamza, Iman,Shaker, Olfat,Yosry, Ayman Asian Pacific Journal of Cancer Prevention 2016 Asian Pacific journal of cancer prevention Vol.17 No.5
Background: Primary hepatocellular carcinoma (HCC) is one of the most common malignancies worldwide. MicroRNAs (miRNAs) have great HCC diagnostic potential and circulating miRNAs have been reported as promising biomarkers for various pathologic conditions. Aim: To explore the potential benefit of serum miR-126, miR-129, miR-155, miR-203 and miR-223 as non-invasive diagnostic markers of hepatitis C virus (HCV)-related HCC. Materials and Methods: The expression of miRNA was evaluated using real-time quantitative RT-PCR in 78 serum samples (30 $treatment-na{\ddot{i}}ve$ chronic HCV, 25 post-HCV compensated cirrhosis and 23 $treatment-na{\ddot{i}}ve$ HCC cases). Results: Comparing miRNA fold changes in the HCC group vs the non HCC groups, there was significant fold decrease in miR-126 (P= 0.034), miR-129 (P= 0.006), miR-155 (P= 0.011), miR-203 (P<0.001) and miR-223 (P= 0.013). The highest AUC to differentiate HCC patients from non-HCC was 0.76 for miR-203. Conclusions: Among studied miRNAs, serum miR-203 has the highest potential as a non-invasive biomarker of HCC.
Khairy Fathy,Keiki Morimoto,Ki-Young Suh,Soon-Kurl Kwon,Mutsuo Nakaoka 대한전기학회 2007 Journal of Electrical Engineering & Technology Vol.2 No.1
This paper presents a new circuit topology of active edge resonant snubbers assisted half-bridge soft switching PWM inverter type DC-DC high power converter for DC bus feeding power plants. The proposed DC-DC power converter is composed of a typical voltage source-fed half-bridge high frequency PWM inverter with a high frequency planar transformer link in addition to input DC busline side power semiconductor switching devices for PWM control scheme and parallel capacitive lossless snubbers. The operating principle of the new DC-DC converter treated here is described by using switching mode equivalent circuits, together with its unique features. All the active power switches in the half-bridge arms and input DC buslines can achieve ZCS tum-on and ZVS tum-off commutation transitions. The total turn-off switching losses of the power switches can be significantly reduced. As a result, a high switching frequency IGBTs can be actually selected in the frequency range of 60 ㎑ under the principle of soft switching. The performance evaluations of the experimental setup are illustrated practically. The effectiveness of this new converter topology is proved for such low voltage and large current DC-DC power supplies as DC bus feeding from a practical point of view.
Khairy Fathy,Kwang Ju Choi,Hyun Woo Lee,Mutsuo Nakaoka 대한전기학회 2006 대한전기학회 학술대회 논문집 Vol.2006 No.10
This paper presents the design and implementation of 1㎾ prototype DC-DC power converter with bridge voltage-doubler suitable for small scale PEM fuel cell system and its associated control scheme. The operation principle of this converter is described using some operating waveforms and the switching mode equivalent circuits based on simulation results and a detailed circuit operation analysis and soft-switching conditions.