**A cascaded Couple Inductor- Reverse high step up converter integrating three-winding coupled inductor and diode-capacitor technique**

*Abstract***—**

This paper introduces a cascaded high step up converter realized with a tightly coupled three-winding coupled inductor. Compared with existing high step up conver ters, the proposed converter features that the smaller the turns ratio is, the larger the conversion gain is. So, the name couple inductor- reverse is given to represent reverse coupled inductor principle of operation. In addition, diode-capacitor circuit is introduced to not only recycle leakage energy to output, but also further lift voltage conversion gain. This paper illustrates operation principle of the proposed converter, discusses effect of leakage inductance on voltage gain, and deduces voltage and current stresses of components. Finally, a prototype rated at 400W has been established, and experimental results verify correctness of the above theoretical analysis.

**EXISTING SYSTEM: **

In general, conventional boost converter can satisfy requirement in such applications But, some typical drawbacks exist: the voltage stress of main switch is equal to the output voltage, hence, a high voltage rating switch with high on-resistance should be used, generating high conduction losses. In addition, an extremely high duty ratio will induce large conduction losses on power devices and serious diode reverse recover y problem. Based on the above drawbacks, the conventional boost converter is not suitable for realizing high step-up voltage gain together with high efficiency. Many other techniques have been researched to achieve a high conversion ratio and avoid operating at extreme duty ratio. These techniques include the switches-capacitor techniques , switched-inductor techniques, voltage-lift techniques. All these techniques can obtain higher voltage conversion gain than the conventional boost converter. More components, however, are needed for extremely large conversion ratio, resulting in higher cost and complex circuit. Therefore, to achieve a high conversion ratio without operating at large duty cycle, some papers have focused on coupled inductor technique. Typical isolated fly back converter is often adopted for achieving high voltage gain by adjusting the turns ratio. But, the leakage inductance may cause high voltage spikes on the switch and induce energy losses. In order to improve the problems, passive snubber circuit or active clamp circuit can be applied. But, this makes both cost and circuit high and complex. Many non-isolated converters based on coupled inductor are presented. However, under the condition of large voltage conversion gain, the turns ratio must be ver y high. Using a coupled inductor with a large turn ratio also introduces several problems. For example, the leakage inductance and parasitic capacitance formed by secondary winding of the coupled inductor may cause voltage and current spikes and increase loss and noise that will dramatically degrade the system performance. In order to satisfy the large high step-up applications, cascaded high step-up converters were proposed but, a these converters, the voltage conversion gain is approximately proportional to the turns ratio. Sometimes, the problem of high turns ratio still exists.

**PROPOSED SYSTEM:**

In this paper, a novel cascaded high step-up converter with three-winding coupled inductor and diode-capacitor structures is proposed. The features of the proposed converter are as follows, 1) The smaller the turns ratio is, the higher voltage conversion gain is, 2) The voltage stresses on power switch and diodes are ver y low, this makes low on-resistance mosfet and schottky diodes available, 3) Leakage inductance energy can be recycled to the output, 4) The cascaded structure makes voltage conversion gain higher. ** **

**CONCLUSION **

For the high step-up applications, a novel high voltage gain converter is introduced in this paper, which combines a quadratic boost converter with three-winding coupled inductor and diode-capacitor techniques. The diode-capacitor circuit not only lifts the voltage conversion gain, but also recycled the leakage energy to the output. The three-winding couple inductor-reverse makes the smaller turns ratio available implementing the high voltage conversion gain. Due to cascaded structure, a smaller duty cycle can produce a high conversion gain. The voltage stresses on the power switch and diodes are very low, which makes the low on resistance mosfet and schottky diodes available. The efficiency is improved efficiently.

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