Recent developments in renewable energy sources has created demands for high step-up and high efficiency DC-DC converters. This demands are fulfilled basically through the use of high frequency transformer to achieve the required and desired gain. Power electronics solutions based on multi-converter structures provides economic methods for input and output power by combining a number of components. In this paper some of structures reviewed that have been proposed to achieve a high step-up converter and the advantages and disadvantages of these converters are discussed. The proposed converter is provided in order to reduce the voltage stress of high step-up converters based on coupled inductor and passive clamping circuit. The voltage stress of switches in the proposed converter is less than a simple boost converter also in this structure with using passive clamping circuit the oscillation of both sides of the switches is a little clamped and finally by using this technique it can achieve high gain by selecting the appropriate duty cycle. In this paper to review the principle of operation of the proposed converter theoretical analysis are provided and to verify the results of theoretical analysis of the proposed converter is given with its PSPICE simulation.

DC–DC boost converters are unable to provide high step-up voltage gains due to the effect of power switches, rectifier diodes, and the equivalent series resistance of inductors and capacitors. A high step-up DC-DC converter based on the modified SEPIC converter is presented in this paper. Step up non-isolated converters generally suffer from problems such as high voltage stress and low efficiency. In this study, non-isolated boost converter structures, SEPIC, SEPIC modified circuit, and a proposed converter is studied. Then compare the performance of these typologies is located and presented as a chart. The operation analysis, design procedure for proposed converter is obtaied from 15V input voltage and 150V output voltage and with 100 watts output power. Using the proposed converter, the input inrush current and the invading voltage of the output have decreased. The time response analysis states that the proposed converter acts faster with deployment time than other converters.

High step-up DC-DC converters are considered as main components of some low-voltage and low-power fuel cell power system applications. A new DC-DC converter topology based on a two-stage switched capacitor-switched inductor multiplier is proposed in this paper. In comparison with other conventional and high step-up DC-DC converters, the proposed converter topology provides higher voltage gain and lower switch voltage stresses for the duty cycles in the range of 0.6 or higher, which is the common duty cycle range of high step-up DC-DC converters. The proposed converter consists of a novel combination of switched capacitors and switched inductors methods which lead to the reduced number of required switches and their duty cycles. The theoretical analysis is confirmed by simulation results in MATLAB/Simulink software environment results. A 100 W laboratory prototype of the proposed converter is implemented to investigate and validate the analytical and simulation results. The prototype DC-DC converter is designed and implemented to be used for a commercial 100 W PEM fuel cell stack power system.

In this article, a two-output step-up converter which is suitable for renewable energy applications is proposed. The proposed topology is composed of super lift Luo converter with a switch-capacitor structure to provide a dual-output converter. The proposed non-isolated step-up converter has a simple structure using just one switch and a single inductor for creating a step up two output converter. Circuit theory analyzes are presented in the continuous conduction mode and evaluated by simulation results in OrCAD software. The control system of the proposed 200-watt converter is utilizing one PI in feedback control system. The efficiency of the converter in full load is 94%. The superiority of the proposed converter compared to similar two-output converters is also confirmed.

In this paper, a non-isolated high step-up soft-switching converter is proposed. The proposed converter is a boost converter combined with two voltage multiplier cells for boosting output voltage. Also, extend voltage gain of the proposed converter is achieved by using a coupled-inductor. Compare with other similar high step-up topologies with the same number of components, the proposed converter has a higher voltage gain and higher efficiency. An active clamp circuit is used so, the zero-voltage switching (ZVS) is achieved. Also, in the proposed converter, the voltage stresses on the switches are low. As the voltage stress decreases on the switch, Ron</sub> of the MOSFET is deceased and as a result conduction loss of the switch is decreased. So, the efficiency of this converter increased. In this paper, operational principle of the converter is described and the analytical, simulated results and prototype converters are validated using a 20V input and 400V </strong>output converter at 200W load.

An effective high-step-up DC-DC converter is an important section of renewable energy systems. Cascaded boost converters provide more voltage gain than single boost converters, but they are still unsuitable for high step-up voltage conversion due to gain and hard switching conditions. To improve the voltage, gain of the cascaded boost converter, a coupled inductor can be used but the leakage inductance causes a voltage. To overcome these problems, a high step-up converter is proposed in which a cascaded structure, coupled inductor, and a lossless passive snubber are utilized together. The proposed converter has zero current and zero voltage switching conditions at turn-on and off instants. First, the proposed converter is theoretically analyzed, and then its design and simulation in OrCAD software are presented.  Furthermore, the experimental results of the prototype verify soft switching conditions and high step-up gain.

In some applications that we need a high voltage gain such as the photovoltaic cell and fuel cell, high step up dc-dc converters must be used, but conventional boost converter cannot provide the high voltage gain. For this reason, in this paper, a single switch transformerless high step-up buck boost dc-dc converter with reduced voltage stress on the semiconductors is proposed. The proposed converter has higher voltage gain in step-up mode in comparison with conventional boost and buck-boost converters. Reduced voltage stress on the active switch allows to choose lower voltage rating MOSFETs to reduce both switching and conduction losses. Low voltage stress on the diodes allows the use of Schottky rectifiers for alleviating the reverse-recovery current. The proposed converter can be operated in the continuous conduction mode (CCM) and the discontinuous conduction mode (DCM). In this paper, different operation modes of the proposed converter, calculation of the voltage gain, the currents that flow through the components, efficiency and capacitors voltage ripple are presented. To verify the operation of the proposed converter, simulation results via PSCAD software and experimental results are provided.

This paper focuses on introducing a transformerless DC/DC converter with low total switching device power in dual working modes including step-up and step-up/down modes. The proposed converter is analysed in terms of the continuous conduction mode, steady state, and efficiency with the replacement of parasitic resistance effects. The proposed converter in the step-up mode has a high voltage gain ratio and a continuous input current. Then, the other working mode of the proposed converter with relevant DC/DC converters is compared. By this comparison, the proposed converter has a high voltage gain ratio. Also, the converter characteristics such as voltage stress on power switches and charge pump capacitors are in a good condition in this mode. Finally, the experimental results from a laboratory made prototype and the obtained waveforms from the simulation in PLECS are presented for validation such as higher voltage gain ratio, lower total switching device power and better efficiency.

In this paper, an interleaved high step-up converter with a simple auxiliary circuit is presented. The proposed auxiliary circuit has the coupled inductor with the input inductors of the converter and provides zero voltage switching conditions for the main switches of the converter. On the other hand, auxiliary switches and diodes of auxiliary circuit operate under zero current condition and therefore do not impose significant losses on the converter. The auxiliary circuit is modular and can apply to more phases of the converter. Therefore, the converter can be easily designed for very high power applications. The proposed converter uses the cross-coupled inductors technique with series lift capacitors to increase the voltage gain and reduce the voltage stress on the main switches. Also, leakage inductance energy can be easily absorbed by the clamp capacitors and helps to increasing the voltage gain. The proposed high step-up converter has been analyzed in detail and a practical prototype has been implemented at 100W. The experimental results confirm the correctness of the operation of the circuit and the theoretical analysis.

In this paper, a new high step-up converter is presented. In the proposed converter, a quasi Z-source converter is used and its voltage gain is increased via using coupled inductors. In this way, moreover to the voltage gain, the voltage stress of the switches are improved. In order to provide the soft-switching condition, an auxiliary circuit is used in which only a switch, a diode, and a coupled inductor are needed. In the proposed converter the voltage stress of both switch are much smaller than the output voltage. Another advantage of the proposed converter is having a common ground between input and output. In this paper, at first other high step-up converters which are published in the literature are explained and reviewed to find out the main challenges in high step-up application. Then, the proposed converter and its operational principals alongside with its design procedure are presented. After that, in order to justify the analysis, the simulation and experimental results of the converter are reported. Then, a comparison between the proposed converter and some other high step-up converters are made to show the converter effectively.