DC–DC converters with voltage boost capability are widely used in a large number of power conversion applications, from fraction-of-volt to tens of thousands of volts at power levels from milliwatts to megawatts. The literature has reported on various voltage-boosting techniques, in which fundamental energy storing elements (inductors and capacitors) and/or transformers in conjunction with switch(es) and diode(s) are utilized in the circuit. These techniques include switched capacitor (charge pump), voltage multiplier, switched inductor/voltage lift, magnetic coupling, and multistage/-level, and each has its own merits and demerits depending on application, in terms of cost, complexity, power density, reliability, and efficiency. To meet the growing demand for such applications, new power converter topologies that use the above voltage-boosting techniques, as well as some active and passive components, are continuously being proposed. The permutations and combinations of the various voltage-boosting techniques with additional components in a circuit allow for numerous new topologies and configurations, which are often confusing and difficult to follow. Therefore, to present a clear picture on the general law and framework of the development of next-generation step-up dc–dc converters, this paper aims to comprehensively review and classify various step-up dc–dc converters based on their characteristics and voltage-boosting techniques. In addition, the advantages and disadvantages of these voltage-boosting techniques and associated converters are discussed in detail. Finally, broad applications of dc–dc converters are presented and summarized with comparative study of different voltage-boosting techniques.

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Step-Up DC–DC Converters: A Comprehensive Review of Voltage-Boosting Techniques, Topologies, and Applications

A few simple switching structures, formed by either two capacitors and two-three diodes (C-switching), or two inductors and two-three diodes (L-switching) are proposed. These structures can be of two types: ldquostep-downrdquo and ldquostep-up.rdquo These blocks are inserted in classical converters: buck, boost, buck-boost, Cuk, Zeta, Sepic. The ldquostep-downrdquo C- or L-switching structures can be combined with the buck, buck-boost, Cuk, Zeta, Sepic converters in order to get a step-down function. When the active switch of the converter is on, the inductors in the L-switching blocks are charged in series or the capacitors in the C-switching blocks are discharged in parallel. When the active switch is off, the inductors in the L-switching blocks are discharged in parallel or the capacitors in the C-switching blocks are charged in series. The ldquostep-uprdquo C- or L-switching structures are combined with the boost, buck-boost, Cuk, Zeta, Sepic converters, to get a step-up function. The steady-state analysis of the new hybrid converters allows for determing their DC line-to-output voltage ratio. The gain formula shows that the hybrid converters are able to reduce/increase the line voltage more times than the original, classical converters. The proposed hybrid converters contain the same number of elements as the quadratic converters. Their performances (DC gain, voltage and current stresses on the active switch and diodes, currents through the inductors) are compared to those of the available quadratic converters. The superiority of the new, hybrid converters is mainly based on less energy in the magnetic field, leading to saving in the size and cost of the inductors, and less current stresses in the switching elements, leading to smaller conduction losses. Experimental results confirm the theoretical analysis.

Switched-Capacitor/Switched-Inductor Structures for Getting Transformerless Hybrid DC–DC PWM Converters

This paper introduces the use of the voltage multiplier technique applied to the classical non-isolated dc-dc converters in order to obtain high step-up static gain, reduction of the maximum switch voltage, zero current switching turn-on. The diodes reverse recovery current problem is minimized and the voltage multiplier also operates as a regenerative clamping circuit, reducing the problems with layout and the EMI generation. These characteristics allows the operation with high static again and high efficiency, making possible to design a compact circuit for applications where the isolation is not required. The operation principle, the design procedure and practical results obtained from the implemented prototypes are presented for the single-phase and multiphase dc-dc converters. A boost converter was tested with the single-phase technique, for an application requiring an output power of 100 W, operating with 12 V input voltage and 100 V output voltage, obtaining efficiency equal to 93%. The multiphase technique was tested with a boost interleaved converter operating with an output power equal to 400 W, 24 V input voltage and 400 V output voltage, obtaining efficiency equal to 95%.

Voltage Multiplier Cells Applied to Non-Isolated DC–DC Converters

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 DC-DC converter topology is proposed. The DC-DC multilevel boost converter (MBC) is a pulse-width modulation (PWM)-based DC-DC converter, which combines the boost converter and the switched capacitor function to provide different output voltages and a self-balanced voltage using only one driven switch, one inductor, 2
 N
-1 diodes and 2
 N
-1 capacitors for an Nx
 MBC. It is proposed to be used as DC link in applications where several controlled voltage levels are required with self-balancing and unidirectional current flow, such as photovoltaic (PV) or fuel cell generation systems with multilevel inverters; each device blocks only one voltage level, achieving high-voltage converters with low-voltage devices. The major advantages of this topology are: a continuous input current, a large conversion ratio without extreme duty cycle and without transformer, which allow high switching frequency. It can be built in a modular way and more levels can be added without modifying the main circuit. The proposed converter is simulated and prototyped; experimental results prove the proposition's principle.

A DC-DC multilevel boost converter

With reference to a recently published paper, the realization of line and load regulation in switched-capacitor-based converters is discussed. We point out that achieving zero-current switching at the expense of losing line and load regulation is not practically feasible

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Comments on "Design and analysis of switched-capacitor-based step-up resonant Converters"

A high-voltage zero-voltage-zero-current-switched dc--dc converter with low voltage stress is presented in this paper. Its circuit structure is extended from a previously developed zero-voltage-switched dc--dc converter consisting of six series-connected switching devices, one three-phase transformer, and an output current tripler. The voltage stress on each switching device is only one-third of the input voltage. Compared with the previous converter, apart from retaining the advantage of having low voltage stresses on the switches, the main advancements of the proposed converter have also included (1) wider soft-switching range; (2) elimination of circulating energy on the primary side during the freewheeling stage; and 3) use of phase-shift pulsewidth modulation in output voltage control. Detailed topological operations and steady-state characteristics of the converter will be given. A 2.2-kW, 990-V/110-V dc--dc converter prototype has been built and tested. Experimental results are favorably compared with the theoretical predictions.

A High-Voltage ZVZCS DC--DC Converter With Low Voltage Stress

Three basic switching structures are defined: one is formed by two capacitors and three diodes; the other two are formed by two inductors and two diodes They are inserted in either a Cuk converter, or a Sepic, or a Zeta converter The SC/SL structures are built in such a way as when the active switch of the converter is on, the two inductors are charged in series or the two capacitors are discharged in parallel When the active switch is off, the two inductors are discharged in parallel or the two capacitors are charged in series As a result, the line voltage is reduced more times than in classical Cuk/Sepic/Zeta converters The steady-state analysis of the new converters, a comparison of the DC voltage gain and of the voltage and current stresses of the new hybrid converters with those of the available quadratic converters, and experimental results are given

Switched-capacitor (SC)/switched inductor (SL) structures for getting hybrid step-down Cuk/Sepic/Zeta converters

This paper presents the generalized circuit structure of a switched-capacitor DC/DC converter that can offer features of voltage step-down, voltage step-up, and bi-directional power flow, Starting with the derivation of a single-capacitor bidirectional converter cell, a converter string is created by cascading a required number of cells, which is determined by the input and output conversion ratio for optimizing the conversion efficiency. The input current is made continuous by operating two strings in parallel and in anti-phase. State-space averaging technique is applied to study the static and dynamic behaviors.

Development of a generalized switched-capacitor DC/DC converter with bi-directional power flow

A new soft-switching full-bridge current-driven DC-DC converter is proposed for high voltage and high power applications: its power transistors turn-on/off with ZCS, what is suitable for IGBT switches. An active snubber formed by two active switches and one capacitor is inserted in the primary side of the converter. The snubber's accumulated energy is proportional to the input current, what allows ZCS at a very wide line and load range, by minimizing the required energy: for each value of the input current and load, the snubber's capacitor is charged only at the minimum voltage necessary for achieving ZCS. Thus, the level of the snubber energy necessary for soft-switching is self-adaptable. The duration of the resonant stages required for achieving the ZCS conditions are very short and independent of the values of the input current and load. No resonant current peaks appear. The experimental results obtained on a 3 kW prototype, built for the input voltage of 250 V and output voltage of 15 kV, confirmed the expected performances.

A. Ioinovici

Papers

Comments on "Design and analysis of switched-capacitor-based step-up resonant Converters"

A High-Voltage ZVZCS DC--DC Converter With Low Voltage Stress

Switched-capacitor (SC)/switched inductor (SL) structures for getting hybrid step-down Cuk/Sepic/Zeta converters

Development of a generalized switched-capacitor DC/DC converter with bi-directional power flow

A ZCS full-bridge PWM converter with self-adaptable soft-switching snubber energy