High Step-up Converter Research Articles

Novel non‐isolated high step‐up converter with fewer passive devices and low voltage stress of power switches

High step-up, high-efficiency and cost-effective dc–dc converters with high power density, as an interface to boost the low voltage of alternative sources to the utility voltage level, are an important part of renewable energy systems. In this study, a novel high step-up converter is proposed with a switched-capacitor. By introducing the switched-capacitor unit in the converter, the voltage of the switched-capacitor is coupled into the charging circuit of the input filter-inductor. Thus, the boost factor can be enlarged up to (1 − 2D) and the problem of the inrush current can be avoided due to the filter inductor. By replacing the filter inductor with the voltage multiplier unit, the boost coefficient of one coupled inductor voltage multiplier is increased to 2n and the voltage stress of the power switch is significantly reduced. Moreover, the energy of the leakage inductor is recycled by the switched-capacitor with the reduction of the voltage spike and the switches’ stress. The working principle and the steady-state characteristics are analysed in detail in this study, and a comparison is made between the proposed converter and other high step-up converters. The experimental results based on a 200 W 20 to 200 V prototype verify the correctness and the feasibility.

General Method for Synthesizing High Gain Step-Up DC–DC Converters Based on Differential Connections

This article introduces a powerful methodology to synthesize high gain step-up dc–dc converters from differential connections of two converters. The two selected converters may be either equal or different, and they can use different kinds of gain cells. Both only have to present a common reference between the input and output voltages and the same output voltage polarity. The proposed differential connection supplies high step-up converters and mainly the method can be applied to synthesize different topologies from different well-known converters. Besides the derivation and analysis of some converters in continuous conduction mode, the article also discusses the power processing, reduction of components, addition of gain cells to further increase the gain, different kinds of modulations, and addresses a different point of view for some topologies previously published in literature. The proposed methodology is verified through thirteen prototypes derived from basic converters considering input voltage of 20 V, duty cycle of 0.75, switching frequency of 50 kHz and rated power of 100 W. Moreover, three new ultrahigh gain dc–dc converters are still derived from the insertion of gain cells in the differential converters herein proposed. These three converters are experimentally evaluated under input voltages of 20 and 30 V, rated power of 200 W and, switching frequency of 50 kHz, providing static gains from 15 up to 30, and peak efficiency of 96.78%.

A Novel Interleaved High Step-Up Converter With Built-In Transformer Voltage Multiplier Cell

In this article, we propose a novel interleaved high step-up converter. The proposed converter integrates the built-in transformer voltage multiplier cell (VMC) to the interleaved boost converter with voltage lift capacitor. The voltage gain is increased by both of the turns ratio of the built-in transformer and the voltage lift capacitor. Hence, there is no need to operate the converter around unity duty cycles to obtain high voltage gains. Meanwhile, the voltage stress across semiconductors is reduced considerably, facilitating the utilizing of mosfets with low on-state resistance and diodes with low forward voltage drop decreasing the conduction losses. The leakage inductance of the built-in transformer not only provides zero current switching (ZCS) for mosfets but also controls the falling current rate of the diodes alleviating the reverse current recovery problem. In addition, the energy of the leakage inductance is recycled by the clamp capacitor avoiding high spikes across switches. In comparison with the recently published converters, the proposed converter introduces all of the abovementioned advantages with a low number of components that make it an interesting solution for high efficiency and high step-up applications. Finally, a 40-V to 580-V prototype with 930 W power is fabricated to explore the merits of the proposed converter.

A Coupled Inductor Based High Step-Up Converter for DC Microgrid Applications

A high gain nonisolated dc-dc converter is proposed for the distributed generation systems. High voltage gain is achieved by integrating different methods with reduced duty ratio. Inductive voltage spikes across MOSFETs are alleviated and stress is reduced with inclusion of a passive-clamp circuit. Thus, lower voltage rating (small R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ds(ON)</sub> ) active devices can be adopted. Using this clamp, zero-voltage switching over wide load range is achieved for both the MOSFETs. In addition, leakage energy of the coupled inductor is recycled without using auxiliary switch and thus, the gain get further improved. Zero-current switching is obtained for all the diodes using quasi - resonance principle, which diminishes voltage spikes across the diode caused by the parasitic ringing between leakage inductance and diode's stray capacitance. Therefore, snubbers are not necessary to protect the diodes and to mitigate reverse-recovery losses. Overall efficiency improves because of lower switching and conduction losses of the semiconductor devices. A 600 W prototype working at 75 kHz is built in the laboratory to verify the performance. The peak efficiency is nearly 96.5% and is above 95% for wide load range.

High Buck in Buck and High Boost in Boost Dual-Mode Inverter (Hb2DMI)

The application of the dual-mode time-sharing technique in novel transformerless photovoltaic (PV) inverters is proposed and investigated. The simultaneous high step-down or high step-up conversion with 97.6% peak efficiency and injected current with total harmonic distortion <; 2% are achieved. The leakage current problem, which is a main concern with the transformerless PV inverters, is around 20 mA. The indirect current control, especially at transition of modes of operation is highly improved by utilizing a fast dead-beat control scheme. The working principles of the proposed converter show that the step-down and the step-up voltage gains are (D/(1-D)) <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> and D/(1-D) <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> , respectively. Furthermore, a 1 kW, 220 VAC and 200 VDC experimental prototype is implemented to confirm the theoretical achievements.

Analysis and design of an isolated high step‐up converter based on the secondary side quasi‐resonant loops

In a high step-up converter, the primary side input current contributes a significant share of total power loss. Meanwhile, high-voltage stresses of secondary side components are also big issues. This study proposes an isolated converter with secondary side quasi-resonant loops. The push–pull structure is adopted to reduce active switch numbers so the primary side power loss can be controlled in a very minor range. The newly added resonant loops on the secondary side significantly decrease the current stresses of the resonant capacitors, so the power loss caused by capacitor equivalent-series-resistance is reduced. The voltage stresses of diodes and capacitors on the secondary side are also decreased by an improved symmetrical-voltage-quadrupler-rectifier structure. The proposed converter is with the maximum voltage gain equal to 4 without consideration of the transformer. Therefore, it is helpful to decrease the transformer turns ratio. The operation process is analysed in detail and the design considerations are also summarised. Theoretical analysis is verified by the experimental results of a 400 W prototype with 34–40 V input and 380 V output.

Nonisolated High Step-Up Soft-Switching DC–DC Converter With Interleaving and Dickson Switched-Capacitor Techniques

In this article, a nonisolated high step-up soft-switching dc-dc converter is proposed, which is based on a hybrid structure comprising an interleaved boost converter and Dickson switched-capacitor (SC) networks. The high voltage gain can be achieved by the SC networks without an extremely large duty cycle, and the voltage stresses of all the active switches and diodes are kept at levels much lower than the output voltage. Compared with the traditional SC converters, the proposed converter can achieve continuous voltage regulation by the pulsewidth modulation (PWM) technique. The interleaving operation can reduce the input current ripple and improve the power capacity. Resonant inductors with small inductances are inserted into the SC networks to avoid the high current spikes that occur in the traditional SC converters. All the active switches can achieve zero-voltage switching (ZVS) turn-on. Some of the diodes can achieve zero-current switching (ZCS) turn-off, and the other diodes achieve reduced turn-off ${di/dt}$ rates. The operating principle and essential steady-state characteristics of the converter are analyzed in detail. Finally, a prototype converter with an input voltage of 25–40 V, an output voltage of 400 V, and a rated power of 1 kW is designed and implemented to verify the theoretical analysis.

Switched-Capacitor and Coupled-Inductor-Based High Step-Up Converter With Improved Voltage Gain

Based on a hybrid technique of coupled inductor (CL) and switched capacitor, a high step-up dc–dc converter is developed in this article. It consists of one active switch, one CL, four diodes, and four capacitors. The active switch withstands low voltage stress and all diodes’ voltage stresses do not exceed half of the output voltage. Simple structure and low-voltage-rated switches contribute to high efficiency of the proposed converter. The converter provides the ideal voltage gain of ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2 + 2\,\,n) /(1 - d)$ </tex-math></inline-formula> , here <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$n$ </tex-math></inline-formula> represents the turns’ ratio of the CL and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$d$ </tex-math></inline-formula> is the duty ratio. Its circuit configuration and operation principle are introduced. Effects of leakage inductance of the CL and parasitic resistance of components are analyzed in detail. The experimental results demonstrate the effectiveness of the proposed converter and the maximum efficiency is above 97%.

A Thorough Analysis for the Impact of the Coupling Coefficient on the Behavior of the Coupled Inductor High Step-Up Converters

In this article, the impact of the coupling coefficient K on the static continuous conduction mode (CCM) dc voltage gain of the basic passive clamp coupled inductor boost converter is investigated. First, an analytical method for the extraction of the accurate static CCM dc voltage gain and all the necessary formulas for the comprehensively description of the operating behavior of the converter is presented. Next, a comparison between the previous methods from which the proposed approximate static CCM dc voltage gain formulas are derived and the proposed one takes place. Subsequently, from the analysis and the plots, it appears that the coupling coefficient creates a dependence on the operation by the output current of the converter, which is more intense as the coupling coefficient decreases. Furthermore, it is concluded that the decrease in the dc voltage gain depends not only on the coupling coefficient K , but also on the turns ratio of the coupled magnetic component. Finally, experimental results based on a 250-W laboratory prototype with four different magnetic components are presented for the evaluation of the theoretical analysis.

A novel non-isolated high step-up DC–DC boost converter using single switch for renewable energy systems

Nowadays, with the high-power demand in industries, the need for high step-up converters has been a crucial part of interest. Power conservation is an essential aspect of innovation leading to improving the voltage gain of conventional converters such as boost, Cuk and SEPIC. Boosting techniques including voltage multiplier (VM) cells, voltage lift capacitors, coupled inductors, switched capacitor/inductor, etc., are used to enhance the conventional converters to meet high-voltage requirements of various applications. This paper proposes a new high voltage gain DC–DC converter using a coupled inductor and VM cell. The operation of the converter is based on charging the capacitor using a single MOSFET switch and adding it in series with the source to the load. Besides, a passive clamp circuit which is comprised of capacitor and diode has been selected over the active clamp to reduce the voltage stress on the MOSFET switch, which helps to improve the voltage gain of the converter. The turns ratio of the coupled inductor is chosen appropriately to get the required voltage gain. Reduction in voltage stress results in selecting MOSFET with small on-state resistance (Rds-on), which offers less conduction loss and high efficiency of the converter. The proposed converter is modeled, analyzed and simulated using PLECS simulation software. The results are experimentally verified by developing 150 W experimental prototype.

Hybrid Nonisolated Active Quasi-Switched DC-DC Converter for High Step-up Voltage Conversion Applications

This paper deals with a hybrid non-isolated active quasi-switched dc-dc converter with a high-boost voltage gain, which is applicable for the high step-up low power applications. By using fewer number of components in circuit topology, the proposed converter can provide higher-gain voltage with a small duty cycle, which can reduce the voltage stress and conduction loss on power switches. In addition, it draws continuous input current, has lower diode voltage stress and lower passive component voltage ratings. The operating principles and key waveforms in continuous conduction mode and discontinuous conduction mode are presented. Small-signal dynamic analysis, parameter design guideline, power loss calculation, and characteristics comparison with other non-isolated converters have been completed. Finally, a 250W hardware prototype is constructed and the experimental results are presented to verify the feasibility of the proposed converter.

Soft-Switching High Gain Step-Up DC/DC Converter without Auxiliary Switches

This manuscript presents a novel high gain, high efficiency Soft-switching high step-up DC/DC converter for battery-operated vehicles. The high step-up converter can transfer the power flow from the small voltage to high voltage. The conventional two input inductor hard switched non-isolated DC-DC converter improved with an additional auxiliary cell to attain the Zero voltage switching, due to obtaining the softswitching the efficiency may improve and reduces the stress across the main switches. The isolated converters are used as a transformer to attain high gain, whereas in the proposed converter obtains the high gain without a transformer and contains the high efficiency in the step-up mode of operation. The main aim of the converter is to attain the Zero voltage switching without using any additional auxiliary switches. In this paper, the input voltage applied as 30V, and the obtained output voltage is fifteen times to the applied voltage, which is 450V and the output power 850W. This paper mainly presents the theoretical analysis of converter operation and the evaluation of the simulation results validated with the theoretical analysis.

Analysis and Design of Multiphase, Reconfigurable Switched-Capacitor Converters

A comprehensive framework for the analysis and design of multiphase, reconfigurable switched-capacitor (SC) dc-dc converters is presented. A generalized method, utilizing graph theory and network analysis, is first proposed, which enumerates all attainable ideal conversion ratios for a given SC converter structure. From this analysis, the performance limits of multiphase SC converters are expanded, and a reconfigurable, multiphase SC dc-dc converter is proposed. The converter utilizes a programmable and optimized switching configuration that can generate an increased number of attainable ideal conversion ratios for the given number of capacitors and switching states. This property allows the converter to maintain high efficiency across a wide range of operating conditions and achieve very high step-up and step-down conversion ratios. A set of sample switching sequences are provided to generate any attainable ideal conversion ratio, for up to four capacitors, using a minimal number of switching states. An experimental prototype of the converter has been designed and fabricated as an integrated circuit using 0.35-μm CMOS technology to validate the performance.

Very High Step-Up Converter with Switched Capacitor and Coupled Inductor

To increase the voltage gain of power electronic circuits, numerous converters have been designed by researchers. In particular, step-up converters are used in various circuits and systems due to their reliability. Mostly, in some studies, researchers proposed to use coupled inductors and switched capacitors. Therefore, in this study, we aim to use new-generation E-HEMT switches by using a hybrid topology which includes both a switched capacitor and a coupled inductor to deliver ultra-high voltage to the output. The proposed switched capacitor-based hybrid converter (SCBHC) is modeled in Simulink and PowerSim to verify the analytical voltage gain derivations. The proposed SCBHC is compared with a traditional boost converter, a switched capacitor-based topology and two different coupled inductor-based schemes in terms of gain performance for different duty cycles, switching frequencies and turn ratios. With this combined design, we obtain approximately 300–400% more voltage gain than a traditional boost converter. The proposed SCBHC provides a considerable gain and a wide output voltage range with lower turn ratios compared with other topologies.

Novel Isolated Bidirectional Interleaved Converter for Renewable Energy Applications

In this paper, a high-efficiency isolated bidirectional interleaved converter (IBIC) is proposed for high stepup and high step-down conversion systems. Two inductors are used in the low-voltage side to reduce the current ripple. The IBIC incorporates an ideal transformer to achieve energy transformation and galvanic isolation; the voltage doubler circuit in the high-voltage side not only improves the voltage gain but also minimizes the voltage stress of power switches. Clamp capacitors achieve active clamping, and the energy stored in the leakage inductance is recycled. Moreover, some switches are operated with soft-switching and slightly reduced switching losses. The prototype circuit, with low-side voltage V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">L</sub> of 48 V, high-side voltage V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">H</sub> of 380 V, and rated power of 1.5 kW, is implemented to demonstrate the functionality of the proposed IBIC. The peak efficiency levels of the proposed converter in the high step-up and high step-down stages are 95.3 and 95.8%, respectively.

High Step-Up Gain DC–DC Converter With Switched Capacitor and Regenerative Boost Configuration for Solar PV Applications

Because of cost, size, and weight, the transformer is the primary burden in grid-connected solar PV-system and it decreases the whole system efficiency. In order to avoid the use of a transformer, a high step-up gain dc-dc converter is proposed by combining the switched capacitor and regenerative boost (SCRB) configuration in this brief. In classic boost type and derived converters, the device stresses and losses associated with the converter are high and result in lower efficiency. In the proposed converter, the SCRB operations take place simultaneously using lossless passive components and a minimum number of semiconductor devices. Thereby, it drastically increases the dc-voltage gain and enhances efficiency. In addition, it also dominates with fewer ripple content, which helps to elongate the lifetime of devices and suppress the electromagnetic interference. This brief describes detailed steady-state waveforms and various modes of operation under continuous conduction mode and discontinuous conduction mode. This brief also presents the performances of the proposed converter and compares with conventional converters characteristics. A 500 W experimental model has been built to validate the operation and confirms the theoretical waveforms with experimental results. The maximum efficiency of 95.60% is obtained at 480 W for the proposed converter.

Interleaved High Step-Up Converter With Coupled Inductor and Voltage Multiplier for Renewable Energy System

Interleaved High Step-Up Converter With Coupled Inductor and Voltage Multiplier for Renewable Energy System

A New Triple-Switch-Triple-Mode High Step-Up Converter With Wide Range of Duty Cycle for DC Microgrid Applications

DC microgrid is gaining attraction and a recent trend in distribution power generation system due to penetration of renewables (especially photovoltaic or fuel cell). In this paper, a new triple-switch-triple-mode high step-up converter (TSTM-HS converter) is presented for dc microgrid applications. In the proposed converter, voltage lift technique is employed and range of duty cycle is extended by incorporating an additional switch in converter circuitry. By doing this, high voltage conversion ratio is achieved without using a transformer, coupled inductor, and multiple stages of switched capacitors. Moreover, the TSTM-HS converter operated in three modes with two types of the duty cycles to achieve low to high voltage conversion without using high duty cycle for each switch. The effects of difference in the inductance values on the regulation and operating behavior of the TSTM-HS converter are discussed. The continuous conduction mode and discontinuous conduction mode characteristics of the TSTM-HS converter are discussed in detail with steady-state analysis and boundary condition. The comparison is provided to highlight the benefits of the TSTM-HS converter. The selection of semiconductor devices and the design of reactive components are discussed for the TSTM-HS converter. The experimental results of the proposed converter are provided which validate the theoretical approach, performance, and feasibility of converter.

A Three-Switch-Based Single-Input Dual-Output Converter With Simultaneous Boost &amp; Buck Voltage Conversion

With the increasing demand of applications that have two different output voltages, the single-input dual-output (SIDO) converter with fewer components is becoming the cost-effective option instead of employing two single-input single-output converters. However, the cross-regulation of different outputs is still a challenge in SIDO converters design. To save cost and obtain improved cross-regulation performance, a novel SIDO converter consisting of three active switches is proposed in this article. Owing to the use of a voltage multiplier circuit, a high step-up voltage conversion ratio is achieved with relatively low voltage stress of switches. Thanks to the independent power flow and two control variables, the cross-regulation performance is improved, and simultaneous buck as well as boost output voltages is realized. Additionally, all switches can achieve zero-voltage switching operation, which contributes to a significant switching loss reduction. The operation characteristics, design considerations, and control strategy of the proposed converter are analyzed. To verify the theoretical analysis and measure the power efficiency, a prototype circuit with 48 V input and 24 V/2 A, 200 V/1 A outputs is built.

Reduced‐order small signal modelling of high‐order high step‐up converters with clamp circuit and voltage multiplier cell

Generally, the modelling of high step-up converters with a large number of passive components consisting of inductors, coupled-inductors (CL) and capacitors is very complex. Recently, to further increase the voltage gain in high step-up converters in a simple and low-cost manner, voltage multiplier (VM) circuits have been increasingly used. Also, to reduce the switch voltage spike, clamp circuits are applied. This leads to an increase in the order of systems and operational modes as well. Thus, for simpler modelling and reducing the state variables, the use of reduced-order techniques are required. A general structure for small signal modelling of such converters including passive clamp, CL and VM circuits is presented. For this purpose, an example of these types of converters is selected. At first, a full-order model of this high-order converter is derived using the state-space averaging method. Then, two reduced-order models of the converter are derived and then compared with the full-order model. Also, the small signal and low frequency behaviour is evaluated. In addition, the impact of the parameter variations on the frequency response and stability margin is investigated. Finally, experimental results based on laboratory prototype are presented to verify the validity of the theoretical analysis.