Fernando Lessa Tofoli

Novel Nonisolated High-Voltage Gain DC–DC Converters Based on 3SSC and VMC

This paper introduces a new family of dc-dc converters based on the three-state switching cell and voltage multiplier cells. A brief literature review is presented to demonstrate some advantages and inherent limitations of several topologies that are typically used in voltage step-up applications. In order to verify the operation principle of this family, the boost converter is chosen and investigated in detail. The behavior of the converter is analyzed through an extensive theoretical analysis, while its performance is investigated by experimental results obtained from a 1-kW laboratory prototype and relevant issues are discussed. The analyzed converter can be applied in uninterruptible power supplies, fuel cell systems, and is also adequate to operate as a high-gain boost stage with cascaded inverters in renewable energy systems. Furthermore, it is suitable in cases where dc voltage step-up is demanded, such as electrical fork-lift, audio amplifiers, and many other applications.

A review of single-phase PFC topologies based on the boost converter

The need for solid-state ac-dc converters to improve power quality in terms of power-factor correction (PFC), reduced total harmonic distortion at input ac mains, and precisely regulated dc output have motivated the proposal of several topologies based on classical converters such as buck, boost, and buck-boost. Additionally, novel control techniques dedicated to PFC have also been introduced, motivating the manufacturing of commercial integrated circuits to impose sinusoidal currents in the front-end stage of switch-mode converters. Boost converters operating in continuous current mode (CCM) have become particularly popular because reduced electromagnetic interference (EMI) levels result from its utilization. Within this context, this work deals with a comprehensive review of some of the most relevant ac-dc singlephase boost converters for PFC applications. The evolution of the conventional boost converter is demonstrated in terms of improved characteristics achieved by other boost-based topologies. Besides, it seeks to establish a fast and concise guide on ac-dc boost converters to researchers and experts in power electronics by comparing the topologies.

DC–DC Nonisolated Boost Converter Based on the Three-State Switching Cell and Voltage Multiplier Cells

This work introduces a dc-dc boost converter based on the three-state switching cell and voltage multiplier cells. A brief literature review is presented to demonstrate some advantages and inherent limitations of several topologies that are typically used in voltage step-up applications. The behavior of the converter is analyzed through an extensive theoretical analysis, while its performance is investigated by experimental results obtained from a 1-kW laboratory prototype, as relevant issues are discussed. The converter can be applied to uninterruptible power supplies and is also adequate to operate as a high gain boost stage cascaded with inverters in renewable energy systems. Furthermore, it can be applied to systems that demand dc voltage step up such as electrical fork-lift, renewable energy conversion systems, and many other applications.

Power Factor Correction Boost Converter Based on the Three-State Switching Cell

The need for solid-state ac-dc converters to improve power quality in terms of power factor correction, reduced total harmonic distortion at input ac mains, and precisely regulated dc output has motivated the investigation of several topologies based on classical converters such as buck, boost, and buck-boost converters. Boost converters operating in continuous-conduction mode have become particularly popular because reduced electromagnetic interference levels result from their utilization. Within this context, this paper introduces a bridgeless boost converter based on a three-state switching cell (3SSC), whose distinct advantages are reduced conduction losses with the use of magnetic elements with minimized size, weight, and volume. The approach also employs the principle of interleaved converters, as it can be extended to a generic number of legs per winding of the autotransformers and high power levels. A literature review of boost converters based on the 3SSC is initially presented so that key aspects are identified. The theoretical analysis of the proposed converter is then developed, while a comparison with a conventional boost converter is also performed. An experimental prototype rated at 1 kW is implemented to validate the proposal, as relevant issues regarding the novel converter are discussed.

A Passive Lossless Snubber Applied to the AC–DC Interleaved Boost Converter

High switching frequency operation of static power converters is often required to reduce size, weight, and electromagnetic interference levels, at the cost of increased switching losses and reduced efficiency. Switching losses include the current and voltage overlap loss during the switching interval and the capacitance loss during turn-on. Recently, the use of passive soft switching methods has been emphasized as a better alternative to active methods, mainly because they do not require extra switches or additional control circuitry. This paper proposes a passive lossless snubber applied to the interleaved boost converter. The use of a soft commutation cell causes the main switches to be turned on and off under null current and null voltage conditions, respectively, as high efficiency results over the entire load range. The theoretical analysis including the description of the operating stages and the design procedure are included. Experimental results on a 2 kW prototype are presented and discussed to validate the proposal.

A Nonisolated DC-DC Boost Converter With High Voltage Gain and Balanced Output Voltage

This paper presents a dc-dc boost converter with high voltage gain based on the three-state switching cell for split-capacitor neutral-point-clamped inverters. The proposed converter is analyzed considering the operation in continuous conduction mode and duty cycle higher than 0.5, which corresponds to overlapping mode. The main characteristics of the topology are operation at high switching frequency, whereas the input inductor is designed for twice such frequency; in order to minimize weight and volume, the voltage stress across the switches is lower than half of the output voltage and naturally clamped by one output capacitor, allowing the use of MOSFET transistors with reduced intrinsic on-resistance; the input current presents small ripple; the output voltage can be further stepped up by increasing the transformer turns ratio without compromising the voltage stress across the switches; and the output voltage is naturally balanced, thus making the converter suitable for supplying split-capacitor inverters. Several topologies where a high voltage step-up is possible are initially investigated in the literature. Then, the principle of operation and experimental results for a 1-kW prototype are presented to validate the theoretical analysis and demonstrate the converter performance.

Two-Stage Isolated Switch-Mode Power Supply With High Efficiency and High Input Power Factor

This paper presents the conception and analysis of a switch-mode power supply (SMPS) with desirable characteristics of high-frequency isolation, high input power factor, low harmonic distortion, and high efficiency. Nearly unity input power factor can be obtained by using an interleaved boost converter associated with a nondissipative snubber, as high efficiency of the ac-dc front-end stage results. Additionally, a soft-switching full-bridge topology performs the dc-dc conversion, providing isolation to the SMPS by using a high-frequency transformer. By cascading both stages, the aforementioned characteristics are achieved. Theoretical background on each one of the converters is presented, and experimental results obtained from a laboratory prototype are presented and discussed in order to validate the proposal. In addition, the evaluation tests demonstrate the operation with nearly unity power factor, high efficiency, and good dynamic response over a wide load range.

Proposal of a Soft-Switching Single-Phase Three-Level Rectifier

This paper is concerned with the study of a single-phase boost-type three-level rectifier. The converter is supposed to present high input power factor, low current harmonics, low total harmonic distortion, and simple control scheme. In order to minimize switching losses, a passive nondissipative snubber is associated with the aforementioned converter. The theoretical analysis, design procedure, and analytical results regarding a 1.2-kW prototype are presented to validate the proposal.

A high-power-factor half-bridge doubler boost converter without commutation losses

This paper proposes a high-power-factor half-bridge doubler boost converter without commutation losses, which provides high output voltages, i.e., from 600 to 900 V. The voltages across the semiconductor devices are low and approximately equal to the output voltage, as doubled output voltages and reduced high-frequency ripple can be achieved. A detailed mathematical analysis concerning its operation is presented, and simulation and experimental results describe the converter performance.

Analysis, Design, and Experimentation of a Double Forward Converter With Soft Switching Characteristics for All Switches

The study of a topology resulting from the combination of two forward structures attached to a single transformer core is presented in this paper, as a dual active bridge converter is obtained. In order to reduce the switching losses and the electromagnetic interference, a soft commutation cell, which provides zero-voltage commutation of the main switches for the entire load range, is implemented. Besides, the auxiliary switches are zero-current turned on and zero-current, zero-voltage turned off. This converter reduces the voltage over the main switches to half of the input voltage, employing only four switches and an additional transformer winding when compared to the full-bridge converter. The analysis of the circuit is carried out, and experimental results obtained from a prototype are also presented to support the theoretical assumptions.