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A NOVEL SWITCHED-COUPLED-INDUCTOR DC–DC STEP-UP CONVERTER AND ITS DERIVATIVES ABSTRACT: This paper presents a novel dc–dc converter configuration, which successfully integrates two technologies, including a switched capacitor and a switched coupled inductor, into one converter. By adopting a coupled inductor to charge a switched capacitor, the voltage gain can be effectively increased, and the turns ratio of the coupled inductor can be also reduced. Not only lower conduction losses but also higher power conversion efficiency is benefited from a lower part count and lower turns ratios. The proposed converter is simply composed of six components, which can be further derived to varied converters for different purposes, such as a bidirectional converter. The operating principle and steady-state analysis are discussed in this paper. A 250-W laboratory hardware prototype is completed and verified. The voltage gain is up to 11. The highest efficiency is 97.2%, and the full-load efficiency is kept at 93.6%. INTRODUCTION: Various converters for high step-up applications has included the analysis of the switchedinductor and switched capacitor type, the transformerless switched-capacitor type, and the voltage-lift type. Some converters, which are the combination of boost and flyback converters or the combinations of other types of converters, are developed to carry out a high step-up voltage gain by using a coupled-inductor technique. However, the leakage inductance of the coupled-inductor will cause a high voltage spike on active switches when the switches were turned off. A small resistor or a resistor–capacitor–diode snubber can be used to dissipate this leakage energy and suppress the voltage spike, but these simple solutions are unable to benefit the converter efficiency. Alternatively, employing an active clamp technique to recycle the leakage energy can achieve soft switching for active switches. This active clamp technique directly increases the part count and the complexity of control. Nevertheless, the power conversion efficiency and voltage gain of step-up converters are restrained by either the parasitic effect of passive components, such as the reverse recovery issue of diodes, or the switching losses and conduction losses of power switches. A small resistor or a resistor–capacitor–diode snubber can be used to dissipate this leakage energy and suppress the voltage , but these simple solutions are unable to benefit the converter efficiency. Alternatively, employing an active clamp technique to recycle the leakage energy can achieve soft switching for active switches. This active clamp technique directly increases the part count and the complexity of control. Nevertheless, the power conversion efficiency and voltage gain of step-up converters are restrained by either the parasitic effect of passive components, such as the reverse recovery issue of diodes, or the switching losses and conduction losses of power switches. The proposed converter. Two diodes D1 and D2 and capacitor C1 comprise a conventional voltage-lift network. A coupled inductor T1, along with a single active switch S1, is inserted between capacitor C1 and diodes D1 and D2. Coupled inductor T1 plays the role of energy storage and a transfer device. The magnetizing inductor Lm of coupled inductor T1 is equivalent to the input inductor of a conventional boost converter. Switching capacitor C1 obtains energy from input source Vin and secondary winding N2 and then releases it to output capacitor C2 and load R through output rectifier diode D2. The proposed converter has several features. First, the coupled inductor transfers energy when the active switch is either turned on or turned off, which increases the usage of the coupled inductor. EXISTING SYSTEM: The magnetizing inductance of the high-frequency transformer is used for transferring power. In order to reach an appropriate inductance value, the transformer may need to have an air gap. Two smaller capacitors, C1 and C2, provide partial resonance. These capacitors are placed on both sides of the transformer to also provide paths for the currents of the primary and secondary leakage inductances and subsequently, avoid voltage spikes when the input and output switches are turned OFF. As a result, no extra snubber circuit is required. PROPOSED SYSTEM: Two diodes D1 and D2 and capacitor C1 comprise a conventional voltage-lift network. A coupled inductor T1, along with a single active switch S1, is inserted between capacitor C1 and diodes D1 and D2. Coupled inductor T1 plays the role of energy storage and a transfer device. The magnetizing inductor Lm of coupled inductor T1 is equivalent to the input inductor of a conventional boost converter. Switching capacitor C1 obtains energy from input source Vin and secondary winding N2 and then releases it to output capacitor C2 and load R through output rectifier diode D2. ADVANTAGES: The coupled inductor transfers energy when the active switch is either turned on or turned off. The voltage conversion ratio can be efficiently enlarged. The leakage inductor energy of the coupled inductor can be recycled BLOCK DIAGRAM: Single switch integrated with coupled inductor INPUT DC supply 12 V DC OPTO coupler circuit 5 V DC BUFFER circuit PIC controller circuit TOOLS AND SOFTWARE USED: MPLAB – microcontroller programming. ORCAD – circuit layout. MATLAB/Simulink – Simulation Voltage lift circuit Load APPLICATIONS: DC drives Battery charging systems CONCLUSION: The proposed switched-coupled-inductor converter is a simple dc–dc step-up converter with a high voltage conversion ratio inherent in this converter. By adopting coupled-inductor and switched-capacitor techniques, the proposed converter successfully enlarges the voltage conversion ratio without a high turns ratio of the coupled inductor. The proposed converter can be also expanded to varied converters for different applications by simply adding seriesconnected or parallel-connected modules to it. Finally, the laboratory hardware prototype is implemented, and its performance is verified. The total parts count is only six. The voltage gain is 11 when the turns ratio of the coupled inductor is three. The highest efficiency is up to 97.2%, and the full-load efficiency is kept at 93.6%. REFERENCES: [1] B. Axelrod and Y. Berkovich, “Switched-coupled inductor cell for DC–DC converters with very large conversion ratio,” IET Power Electron., vol. 4, no. 3, pp. 309–315, Mar. 2011. [2] B. Axelrod, Y. Berkovich, and A. Ioinovici, “Switched-capacitor/ switched-inductor structures for getting transformerless hybrid DC–DC PWMconverters,” IEEE Trans. Circuits Syst. I, Reg. Papers, vol. 55, no. 2, pp. 687–696, Mar. 2008. [3] D. Li, P. C. Loh, M. Zhu, F. Gao, and F. Blaabjerg, “Generalized multicell switched-inductor and switched-capacitor Z-source inverters,” IEEE Trans. Power Electron., vol. 28, no. 2, pp. 837–848, Feb. 2013. [4] L. S. Yang, T. J. Liang, and J. F. Chen, “Transformer less DC–DC converters with high stepup voltage gain,” IEEE Trans. Ind. Electron., vol. 56, no. 8, pp. 3144–3152, Aug. 2009.