The major consideration in dc-dc conversion is often associated with high efficiency, reduced stresses involving semiconductors, low cost, simplicity and robustness of the involved topologies. In the last few years, high-step-up non-isolated dc-dc converters have become quite popular because of its wide applicability, especially considering that dc-ac converters must be typically supplied with high dc voltages. The conventional non-isolated boost converter is the most popular topology for this purpose, although the conversion efficiency is limited at high duty cycle values. In order to overcome such limitation and improve the conversion ratio, derived topologies can be found in numerous publications as possible solutions for the aforementioned applications. Within this context, this work intends to classify and review some of the most important non-isolated boost-based dc-dc converters. While many structures exist, they can be basically classified as converters with and without wide conversion ratio. Some of the main advantages and drawbacks regarding the existing approaches are also discussed. Finally, a proper comparison is established among the most significant converters regarding the voltage stress across the semiconductor elements, number of components and static gain.

https://ietresearch.onlinelibrary.wiley.com/doi/pdf/10.1049/iet-pel.2014.0605

Survey on non-isolated high-voltage step-up dc–dc topologies based on the boost converter

A new transformerless buck–boost converter with simple structure is proposed in this study. Compared with the traditional buck–boost converter, the proposed buck–boost converter’s voltage gain is squared times of the former’s and its output voltage polarity is positive. These advantages enable it to work in a wider range of positive output. The two power switches of the proposed buck–boost converter operate synchronously. In the continuous conduction mode (CCM), two inductors are magnetized and two capacitors are discharged during the switch-on period, while two inductors are demagnetized and two capacitors are charged during the switch-off period. The operating principles, the steady-state analyses, and the small-signal model for the proposed buck–boost converter operating in CCM are presented in detail. The power electronics simulator (PSIM) and the circuit experiments are provided to validate the effectiveness of the proposed buck–boost converter.

A New Transformerless Buck–Boost Converter With Positive Output Voltage

In this paper, a new non-isolated Interleaved dc/dc converter with high-voltage conversion ratio is presented. The proposed converter combined with interleaved converter techniques and volt...

High step-up interleaved dc/dc converter with high efficiency

In this article, based on the LLC resonant converter fundamental harmonic analysis model, the modulation strategies for LLC resonant converter can be categorized into the following three groups: 1) input voltage fundamental harmonic modulation; 2) resonant tank elements modulation; and 3) secondary equivalent impedance modulation. Operational principles and control diagrams for different modulation strategies are given. Comprehensive comparisons between these modulation strategies in terms of topology complexity, control complexity, and voltage gain range are presented with respect to the same system specifications. The advantages and disadvantages for each modulation strategy are summarized to provide guidance for engineers when analyzing and designing an LLC resonant converter. The hybrid modulation strategies are categorized into different groups based on the specific applications. Brief introductions of these hybrid modulation strategies are presented. Future trends regarding the modulation strategies of LLC resonant converters are presented.

Overview of Modulation Strategies for LLC Resonant Converter

In this paper, a new structure of nonisolated boost dc–dc converters based on voltage-lift technique is proposed. In comparison with conventional nonisolated boost dc–dc converters, the proposed converter generates higher voltage gain. In this paper, the relations between voltage and current of all elements in continuous conduction mode and discontinuous conduction mode are calculated as well as voltage gain in each mode. Then, the critical inductance and stress of switch current are extracted. Finally, the validity of given theories is examined by using the experimental results.

Voltage-Lift Technique Based Nonisolated Boost DC–DC Converter: Analysis and Design

A kind of interleaved non-isolated high step-up DC/DC converter is presented in this study. The converter consists of two basic Boost cells and some diode-capacitor multiplier (DCM) cells as needed. Because of the DCM cells, the voltage conversion ratio is enlarged and the extreme large duty ratio can be avoided in the high step-up applications. Moreover, the voltage stress of all the power devices is greatly lower than the output voltage. As a result, lower-voltage-rated power devices can be employed, and higher efficiency can be expected. Since the two basic Boost cells are controlled by the interleaving method, which means the phase difference between the two pulse width moderlation (PWM) signals is 180° and the input current is the sums of the two inductor currents, the input current ripple is decreased and the size of the input filter could be reduced, which make it a suitable choice in the photovoltaic power generation system and hybrid electric vehicles, etc. Finally, the experimental results from a 300 W, 30-400 V laboratory prototype are presented to validate the effectiveness of the proposed converter.

Interleaved non-isolated high step-up DC/DC converter based on the diode-capacitor multiplier

The LLC resonant converters have been widely used in many applications due to their features such as wide input voltage range, high efficiency, and high power density. Therefore, the analysis methodology for the LLC resonant converter is of great importance. Based on the existing literature, there are mainly four analysis methodologies: (i) fundamental harmonic analysis; (ii) frequency domain with time domain partial correction; (iii) frequency domain with time domain complete correction; (iv) time domain analysis or operation mode-based analysis. However, there is no systematic view and study on different LLC analysis methodologies. Therefore, the main purpose and contribution of this study are to make a comprehensive study and comparison of these analysis methodologies and to provide guidance on analysing and designing of the LLC resonant converter to the readers. In this study, the principles of these four analysis methodologies are introduced briefly. Then, by introducing gain error and peak gain frequency error as definitions, comprehensive comparison studies on these four different methodologies for different conditions are implemented. Recommended applications for each methodology are summarised; finally, an experimental prototype is built to verify the theoretical analysis, and a conclusion is drawn.

https://ietresearch.onlinelibrary.wiley.com/doi/pdf/10.1049/iet-pel.2019.0027

Comparison among different analysis methodologies for LLC resonant converter

High step-up boost converters with coupled inductor have attracted much attention in the fuel cell or photovoltaic grid-connected generation system, however, there are few literatures elaborated on the construction ideas and derivation methods of them. Accordingly, in order to obtain a clear roadmap on the derivation and inner connection of these converters, a comprehensive review and analysis are presented in this paper. First, the basic boost converter with coupled inductor is regarded as the basic topology, and its merits and demerits are analyzed in detail. Then, in order to address these demerits, various step-up techniques are introduced, such as the rectifier circuit, the active-clamped circuit, the multi-winding coupled inductor, and the voltage doubler rectifier; and numerous new topologies are continuously proposed by combinations and equivalent simplifications. In addition to a detailed synthesis of each topology, a comparative and quantitative analysis among some important converters is presented, and the optimal one is chosen to build a 250 W prototype. Finally, based on comparisons and analysis, the main characteristics and inner connections of these high step-up boost converters with coupled inductor are identified and clarified.

Research on Topology of the High Step-Up Boost Converter With Coupled Inductor

An interleaved high step-up zero-voltage-switching boost converter is proposed in this study. The operating principle and voltage gain ratio of the proposed converter are presented. The variable inductor control method is used to regulate the output voltage and to achieve a high-voltage gain. The design procedure of the variable inductor with a double E core is also presented in detail. Finally, a 40 W prototype with a 12 V input and 100 V output is built to verify the consistency of the theory analysis. The highest efficiency measured is 84.5%.

https://ietresearch.onlinelibrary.wiley.com/doi/pdf/10.1049/iet-pel.2013.0811

Interleaved high step-up zero-voltage-switching boost converter with variable inductor control

In this paper, a high efficiency single stage bi-directional battery charger for light electric vehicles (LEVs) is proposed. In Grid-to-Vehicle (G2V) mode, single stage operation is achieved by sharing switches between totem-pole bridgeless power factor correction circuit (PFC) and bi-directional half-bridge LLC resonant converter; in Vehicle-to-Grid (V2G) mode, by turning off the mode selection switch, the proposed topology changed into the form of a half-bridge LLC resonant converter and a full-bridge inverter. Meanwhile, the magnetic control instead of the widely used frequency control is adopted to achieve a better performance. The control circuit and EMI design is simplified, and constant frequency operation is achieved. By carefully designing resonant tank, zero voltage switching (ZVS) and zero current switching (ZCS) operation for switches are guaranteed. Experimental results about variable inductor are presented and analyzed. A simulation case is introduced to verify the feasibility and validity of the proposed topology.

Si Chen

Papers

Interleaved non-isolated high step-up DC/DC converter based on the diode-capacitor multiplier

Comparison among different analysis methodologies for LLC resonant converter

Research on Topology of the High Step-Up Boost Converter With Coupled Inductor

Interleaved high step-up zero-voltage-switching boost converter with variable inductor control

A High Efficiency Single Stage Bi-directional Battery Charger with Magnetic Control