In this paper, a novel noncoupled inductor high voltage gain single-ended primary-inductor converter (SEPIC) is presented. The proposed converter has various advantages, such as lower voltage stress on the switches, noninverting output voltage, high efficiency, and high voltage gain. Also, the introduced converter has a continuous input current which makes it suitable for renewable energy and fuel cell applications. Moreover, high voltage gain is achieved without using any transformer and coupled inductor, thus there is not any voltage overshoot for the switches during the turn- off process. This effect allows low conduction losses by using lower voltage rating switches and also additional clamping circuit is not needed. The control system of the presented converter is simple and the converter can be easily controlled in continuous conduction mode mode operation. Because, the gating pulses for both of the switches are the same and wide output voltage range is achieved only by changing the duty cycle. Furthermore, the number of the components compared to the other noncoupled inductor, SEPIC-based converters which provide near voltage gain to the proposed converter, is reduced. The detailed operation of the introduced converter and design considerations are discussed. Experimental results are presented to verify the performance of the proposed dc–dc converter.

A Novel High Voltage Gain Noncoupled Inductor SEPIC Converter

This paper presents an interleaved converter that benefits the coupled inductor and built-in transformer voltage multiplier cell (VMC). Compared with the other converters with only a built-in transformer or only a coupled inductor, the combination of these techniques gives an extra degree of freedom to increase the voltage gain. The VMC is composed of the windings of the built-in transformer and coupled inductors, capacitors, and diodes. The voltage stress of MOSFETs is clamped at low values and can be controlled via the turns ratio of the built-in transformer and coupled inductor that increases the design flexibility. Moreover, the energy of the leakage inductances, is recycled to the clamp capacitors which avoids high voltage spikes across MOSFETs. In addition, the current falling rate of the diodes is controlled by the leakage inductances, and the reverse current recovery problem is alleviated. Meanwhile, due to the interleaved structure of the proposed converter, the input current ripple is minimized and the current stress of the power devices is decreased. All of these factors improve the efficiency of the proposed converter in high-current and high-voltage applications. The principle operation and steady-state analysis is given to explore the advantages of the proposed converter. Finally, a 1.3-kW prototype with 50–600 V voltage conversion is built to demonstrate the effectiveness of the proposed converter.

An Interleaved High Step-Up Converter With Coupled Inductor and Built-In Transformer Voltage Multiplier Cell Techniques

This paper presents a hybrid cascaded boost converter, in which the input terminal is interlaced in parallel and the output capacitors embedded in voltage multiplier cells are interlaced in series at the output terminal [input parallel output series boost converter (IPOSB)]. The IPOSB can reduce the input current ripples because two primary windings of coupled inductors are connected in parallel with the cross. The voltage multiplier units combine with diode–capacitor and coupled inductor in the output side are charged and discharged in a series and parallel way. In addition, the leakage inductance of the coupled inductor inhibits the inrush current of the capacitors. Therefore, the IPOSB can attain high gain and lower output voltage ripples under a proper duty cycle, and the leakage energy of coupled inductor can also be recycled to the load. At the same time, the voltage stress of power devices is lowered, so the low voltage level MOSFETs can be adopted to reduce the losses and cost. Meanwhile, the soft switching performance of the zero-current-switching is fulfilled, which reduces effectively switching losses. The operational principle and steady-state performance of the converter are analyzed in detail. The correctness of the theoretical analysis is verified by setting up a 450-W experimental prototype.

A Hybrid Cascaded DC–DC Boost Converter With Ripple Reduction and Large Conversion Ratio

In this paper, a new modified single-switch single-ended primary inductor converter (MS2-SEPIC)-based high step-up dc–dc converter is presented. The proposed topology uses the coupled-inductor (CL) technique and a voltage tripler rectifier, which results in a high voltage gain for the converter. Here, the switching loss has been reduced significantly owing to the quasi-resonance operation of the circuit created by the leakage inductance of the CL along with circuit capacitors. The operational principles and steady-state analysis are discussed. Experimental results based on a 100 W laboratory prototype verify the validity of theoretical analysis.

A Modified SEPIC-Based High Step-Up DC–DC Converter With Quasi-Resonant Operation for Renewable Energy Applications

A new nonisolated high-step-up dc–dc converter based on active switched-inductors and passive switched-capacitors is proposed in this article. The main advantages of the converter are the high voltage gain (higher than 20), high efficiency, reduced voltage stresses, and reduced component count. This article approaches the principle of operation, theoretical analysis, design methodology, and a comparison of the proposed topology regarding other converters from the literature that use similar principles. Finally, the theoretical study is verified from a 200-W prototype designed to accomplish an input voltage of 20 V and an output voltage of 300 V, in which a peak efficiency of 96.2% is reached.

Nonisolated High-Step-Up DC–DC Converter Derived from Switched-Inductors and Switched-Capacitors

In this paper, a high step-up coupled-inductor cascade boost dc–dc converter with lossless passive snubber is proposed. Although a conventional cascade boost converter has larger voltage gain compared to a boost converter, it is still not suitable for high step-up voltage conversion. In the proposed converter, a coupled inductor is adopted for the cascaded boost converter to further increase the voltage gain. However, a leakage inductance of the coupled inductor causes a high voltage spike at a main switch. A resistor–capacitor–diode snubber is commonly used to simply solve this problem, but it is also the cause of additional power loss. Therefore, the lossless passive snubber is suggested in this paper in order to prevent efficiency drop by a snubber circuit. In conclusion, the proposed converter has high voltage gain and improved power efficiency. Experimental results from an output 400-V 200-W prototype at a constant switching frequency of 50 kHz are presented to verify the performance of the proposed converter.

High Step-Up Coupled-Inductor Cascade Boost DC–DC Converter With Lossless Passive Snubber

This paper proposes a quadratic boost dc–dc converter with a high voltage gain and reduced voltage stresses. The conventional quadratic boost converter has a limited voltage gain, which is not suitable for high-step-up applications with various microgrids. In the proposed converter, to improve the voltage gain beyond that of a quadratic converter, a coupled inductor is adopted. Additionally, passive clamping circuits are applied to reduce the high voltage stresses caused by leakage inductance of the coupled inductor. Hence, additional power losses from the snubber circuit do not occur, and low-voltage-rating switching devices can be utilized for the main switch and output diode. Moreover, the reverse-recovery problem of the output diode can be alleviated by the leakage inductance. Therefore, the total power efficiency is improved. The theoretical analysis of the proposed converter is verified with a 300-V, 120-W prototype.

Quadratic Boost DC–DC Converter With High Voltage Gain and Reduced Voltage Stresses

A single-switch ac–dc light-emitting-diode (LED) driver based on boost-flyback power factor correction (PFC) converter with a lossless snubber is proposed. In the proposed LED driver, the boost PFC module is designed to be operated in the discontinuous-conduction mode to achieve a high power factor. The dc–dc flyback module is designed to provide input–output electrical isolation to improve safety. The lossless snubber circuit clamps the peak voltage spike of switch to a low voltage and the leakage inductor energy is recycled via the dc–dc flyback module. Additionally, a low-voltage-rating capacitor can be used as the dc-bus capacitor because some of the input power is directly conducted to the output; the remaining power is stored in the dc-bus capacitor. Therefore, the proposed LED driver can provide a high power factor and a high power conversion efficiency. These results are verified for an output of 48 V and 2 A for the experimental prototype.

A Single-Switch AC–DC LED Driver Based on a Boost-Flyback PFC Converter With Lossless Snubber

This paper proposes a zero-ripple input-current high-step-up boost–single ended primary inductor converter (SEPIC) dc–dc converter with reduced switch-voltage stress to overcome some drawbacks of the conventional cascaded boost–SEPIC dc–dc converter. In the proposed converter, the input current ripple is significantly removed by the auxiliary circuit at the boost stage and the voltage gain is more increased by using turn ratio of a coupled inductor at the SEPIC stage. Additional, the switch-voltage stress is reduced due to the clamping circuit, and the reverse-recovery problem of the output diode is alleviated by the leakage inductor. Hence, the low-voltage-rating MOSFET, which has low $R_{{{\rm ds(on)}}}$ , can be utilized as a main switch device. Therefore, the total power efficiency is improved. The theoretical analysis of the proposed converter is verified on an output 200-V to 200-W prototype.

Zero-Ripple Input-Current High-Step-Up Boost–SEPIC DC–DC Converter With Reduced Switch-Voltage Stress

This paper proposes an isolated single-ended primary-inductor converter (SEPIC) dc–dc converter with ripple-free input current and lossless snubber. The proposed converter is based on a conventional isolated SEPIC converter to enable electrical isolation and high voltage gain using a coupled inductor. The input current ripple is significantly reduced by utilizing an auxiliary circuit that also functions as a lossless snubber circuit with an additional diode. Moreover, the maximum switch voltage stress is clamped to a low voltage by the snubber circuit. Therefore, a low voltage rating mosfet that has low $R_{{\rm{DS(on)}}}$ can be utilized as a main switch device. Hence, the total power efficiency is improved. Experimental results from a 100 W prototype, which are presented to verify the theoretic analysis and performance of the proposed converter.

Sin-Woo Lee

Papers

High Step-Up Coupled-Inductor Cascade Boost DC–DC Converter With Lossless Passive Snubber

Quadratic Boost DC–DC Converter With High Voltage Gain and Reduced Voltage Stresses

A Single-Switch AC–DC LED Driver Based on a Boost-Flyback PFC Converter With Lossless Snubber

Zero-Ripple Input-Current High-Step-Up Boost–SEPIC DC–DC Converter With Reduced Switch-Voltage Stress

Isolated SEPIC DC–DC Converter With Ripple-Free Input Current and Lossless Snubber