High Turns Ratio Research Articles

Synchronous Dual-Switch Ultrahigh Step-Up DC–DC Converter Based on Coupled Inductor and Voltage Multiplier for Photovoltaic Systems

In this article, an ultrahigh step-up quadratic boost converter is proposed for photovoltaic systems. By integrating with a coupled inductor and a voltage multiplier, the voltage gain can be improved significantly without high turns ratio and the voltage stress across the power switches are alleviated. Thus, low on-resistance of the power switches are available to enhance efficiency. Common ground structure of quadratic boost and synchronous operation of the two switches facilitate the control. Also, the continuous input current promotes the maximum power point tracking (MPPT). Detailed description of the operation principles and steady-state analysis of this converter in CCM and DCM are presented. A 250W rated laboratory prototype is fabricated and verified, demonstrating a maximum efficiency of 96.5%. Moreover, the dynamic response is tested to prove the stability of the proposed converter. Finally, a simulation is built to evaluate the feasibility of MPPT function.

An Extendable Interleaved Quasi Z-Source High Step-Up DC–DC Converter

A quasi z-source high step-up dc–dc converter is proposed here by integrating a coupled-inductor and a quadruple voltage rectifier technique. This converter can be used for high-voltage gain applications, without using extreme duty cycle and transformer high turns ratio values. Furthermore, low-voltage rating <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">mosfet</small> s, which have small <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</small> -resistances, can be used to reduce conduction losses and improve the converter efficiency. Also, single-core coupled inductors with multiwindings are used to reduce the magnetic components count. Using the interleaved technique at the converter input stage reduces the current stresses of the power <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">mosfet</small> s as well as the current stresses of the primary side windings of the coupled inductor. For high power applications, number of the input stage interleaved legs can be properly chosen to reduce the input current and output voltage ripples values, which reduce the input and output filters volumes. Leakage inductances energy recovery is another benefit of the given converter. To confirm performance of the proposed converter and its operating principles, as well as the given simulation results and mathematical analyses, a two-leg topology of the introduced converter has been implemented and tested by applying both interleaved and noninterleaved gate-drive signals at different conditions.

A Coupled Inductor Based Ćuk Microinverter for Single Phase Grid Connected PV Applications

A single phase, single stage, non-isolated microinverter scheme is proposed in this paper which can address the issues that are commonly associated with flyback derived microinverters, such as i) the appearance of high voltage turn OFF spikes across the high frequency switch, ii) the requirement of lossy snubbers to control these voltage spikes, iii) the necessity for high turns ratio of the transformer and iv) poor efficiency due to the involvement of a higher number of components. The proposed topology involves only one high frequency switch. A resonance capacitor is employed which not only controls the turn OFF voltage spikes across this power switch but also ensures zero voltage turn ON (ZVS) for this switch. A coupled inductor based Ćuk configuration is incorporated in this topology wherein the energy trapped in the transformer leakage inductance is fed back to the grid, thereby improving the overall efficiency. Implementation of a dedicated boundary conduction control (BCM) strategy effectively limits the value of overall system ohmic losses and thereby ensures performance with enhanced efficiency. The inverter operating principle, the process for deriving the reference current expression, and the optimum design strategy for the inverter parameters are discussed in detail. A 220 W laboratory prototype is fabricated to validate the efficacy of the proposed scheme.

A novel ultra-high step-up interleaved DC–DC converter based on the three-winding coupled inductor for distributed generation power system

Abstract In this paper, a non-isolated DC–DC converter with three-winding coupled inductors and switched capacitor cells is introduced. More output voltage is acquired without imposing any extreme duty cycle and high turns ratio. With the help of a two-phase interleaved technique, the input current ripple is reduced efficiently. The leakage inductance of coupled inductors causes the reverse recovery problem of circuit diodes to be solved and alleviates them. Leakage energy is also absorbed by switched capacitor cells. One of the advantages of this converter is the reduction of voltage stress of power switches, which leads to a reduction of conduction losses. In this way, low-voltage rated power switches can be used. Creating soft-switching conditions on power switches and high efficiency are also the prominent features of this structure. Laboratory and experimental results were produced and presented by making a prototype of 350 W–18 V/480 V. Their analysis indicates the effective performance of the proposed topology.

Hybrid Resonant Switched-Capacitor Converter for 48–3.4 V Direct Conversion

As the power required by modern data center processors increases, the power architecture must be adapted; for example, 48 V distribution voltage allows to reduce copper losses by a factor 16 with respect to the use of traditional 12 V power architecture. In order to generate the required processor core voltage, a two-stage approach is usually preferred, where the intermediate bus voltage is generated using an unregulated resonant dc–dc converter as, for instance, an <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LLC</i> converter. Compared to <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LLCs</i> , hybrid resonant switched-capacitor converters (ReSCCs) make it possible to achieve large voltage conversion ratios without the need of high turns ratio transformers. In this letter, a novel hybrid ReSCC that performs a 48–3.4 V direct conversion is presented. A prototype of the proposed converter has been implemented, capable of providing a continuous output power of 440 W with a maximum efficiency of 96.3% at 30 A load current.

Planar Piezoelectric Transformer-Based High Step-Down Voltage-Ratio DC–DC Converter

High step-down voltage-ratio converters are widely used in medium-/high-voltage systems, such as solar power equipment and electric charging station as auxiliary power supplies fed from the dc bus. Traditionally, magnetic transformer-based solutions with high turns ratio are implemented for voltage conversion and galvanic isolation. Instead of utilizing electromagnetic coupling, the high-voltage Rosen-type piezoelectric transformer (PT) provides an alternative solution with electro-mechanical coupling, whose equivalent circuit can be represented by a resonant circuit with an ideal transformer. Moreover, the high-voltage Rosen-type PT features natural mechanisms for high-voltage insulation, high-voltage conversion ratio, and a compact planar form factor, which are all beneficiary for a high step-down auxiliary power supply. This article renders a Rosen-type PT-based high step-down voltage-ratio converter with comprehensive analysis and detailed design procedure. To better understand the operating principle, electrical characteristics of the PT are first analyzed. Effects of input and output compensation components of the PT and their tolerance analysis are subsequently discussed to optimize the performance. After that, topologies of both the input inverter and the output regulation stages are selected. The proposed design is finally validated by a planar prototype with 10-mm height, 5 W full output power, 200 V to 1.5 kV input voltage, and 5 V regulated output voltage.

A High Gain DC-DC Converter Based on Coupled Inductor and Switched-Capacitor Cell with Low-Voltage Stress

This paper presents a nonisolated ultrahigh step-up DC-DC converter with an interleaved structure that is suitable for high power and voltage applications. In order to increase the voltage gain, the proposed structure uses coupled inductors and switched-capacitor cells. Achieving this goal is accompanied by avoiding the imposition of any extreme duty cycle or high turns ratio to the converter. The current ripple is reduced due to the use of the interleaved structure. Since the voltage stress of the switches is lower than the output voltage, by selecting the low-voltage rated switches and small RDS(on), the conduction losses are reduced. In addition, alleviating the phenomenon of reverse recovery of diodes and creating soft-switching conditions in MOSFETs, which leads to a reduction of switching losses, are other advantages of the proposed converter. Therefore, there is no need to use clamp circuits in the mentioned structure. The experimental results, using a prototype of 350 W-18 V/400 V, verify the effective performance of the proposed converter.

A new non-isolated interleaved high step-up gain DC-DC converter with reduced voltage stress on switching devices

ABSTRACT This paper proposes a new Non-Isolated Interleaved (NII) high step-up gain DC-DC converter. This new topology aimed for high power applications, which achieves high step-up voltage gain without a high turns ratio n and a high duty cycle. This converter comprised of two-phase interleaved Coupled-Inductors (CIs) integrated with voltage multiplier rectifier and switched capacitor. The key feature of this converter is very low voltage stress on switching devices compares to existing NII high step-up gain topologies for the similar gain. The reduced rating allows the use of low-voltage rating power devices. Besides, the presented converter inherently recycles the leakage energy, and do not require an auxiliary clamp circuit. In addition, the switching operation is free from the reverse recovery problem due to the zero-current-switching. The working principle and performance characteristics of the converter are presented in detail. The analytical study of effect of parasitic parameters on voltage gain and efficiency of this converter is also presented. The performance comparisons with existing NII high step-up gain topologies are provided to highlight the merits of the converter. To verify the correctness of the theoretical analysis, the experimental setup of 300 W is built. The experiments are conducted to boost 24 V–380 V with turns ratio n = 1, and to boost 24 V–580 V with n = 2.

High-Voltage-Gain Soft-Switching Converter Employing Bidirectional Switch for Fuel-Cell Vehicles

Conventional current-fed resonant converter suffers from high turn-off loss over wide range of fuel-cell voltage. To alleviate this problem, we propose high voltage gain current-fed resonant converter that achieves almost ZVS turn-off over a wide range of voltage gain. By employing a bidirectional switch across center nodes of the voltage doubler and corresponding modulation, the presented converter achieved almost ZVS at the turn-off instant; this trait significantly increases the power conversion efficiency even under high frequency operation. The inherent boost function of the current doubler, an additional boosting operation using a bidirectional switch, and double boosting of the voltage doubler enable the presented converter to achieve high voltage gain without having to use a transformer that has a high turns-ratio. Moreover, 180 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$^\circ$</tex-math></inline-formula> phase interleaving reduces the input current ripple to zero. The steady-state operation is analyzed comprehensively, and design considerations of the proposed converter are given. Finally, a prototype with input of 48-72 V, output of 380 V, and rated power of 1 kW is developed to validate the effectiveness and feasibility of the proposed converter.

Resonant converter with less voltage rating of power switches and wide voltage operation

A resonant converter with less voltage rating of power switches and wide voltage operation is investigated in this Letter for medium voltage applications. Four active switches and two split capacitors are adopted on the primary side to reduce the voltage rating on power semiconductors. The resonant converter is adopted in the converter to have a wide soft switching operation range. Two flying capacitors are used in the presented circuit to operate as the resonant capacitor and also to achieve voltage balance of two input split capacitors. The variable winding turns are used on the secondary side to overcome the problem of the limited voltage operation in the conventional resonant converter. If the input voltage is in the low-input voltage range, the low turns-ratio of the power transformer is used to increase the voltage gain of the resonant converter. If the input voltage is in a high-voltage range, then the high turns-ratio of the transformer is adopted to reduce the voltage gain. Thus, the proposed converter can achieve wide input voltage operation. Experimental results with a 0.8 kW prototype are provided to confirm the effectiveness of wide input voltage operation from 260 to 800 V.

A ∼99% η Hybrid Resonant/Coupled ZCS-Voltage-Quadruplers MV SiC Converter Module for DC Grid in Wind Systems

In this article, a hybrid high voltage gain converter module for medium voltage dc conversion in wind energy systems is proposed. The converter consists of step-up resonant circuit with coupled voltage-quadruplers to achieve the step-up voltage conversion function. The coupled voltage-quadrupler modules are connected to the resonant circuit via a 1:1:1 high frequency transformer. As a result, high turns ratio transformers are not required in the proposed design while at the same time, the output voltage of each voltage-quadrupler is well balanced due to the shared coupled-inductor. All the primary side silicon carbide (SiC) MOSFETs and secondary side SiC diodes exhibit zero switching losses. The output voltage of the converter module is controlled with variable frequency control. Simulation results on a 4 MW modular design of SiC-based converter system with 3.3 kV/18 kV, 670 kW per module, and experimental results on a laboratory-scale prototype with per-module rating: 500 V/2.7 kV, 3.7 kW are provided to validate the theoretical analysis and to highlight the merits of the proposed work. Results confirmed that a peak efficiency of close to 99% is achieved in both simulation and experimental works.

An Isolated High Voltage Boost Current-Fed DC–DC Converter Based on 1:1 Transformer Multiplier Cells and ZVS Operation

This paper presents a high step up, current fed, interleaved, isolated DC–DC converter with voltage multipliers and ZVS (zero voltage switching). The converter provides zero voltage switching for all active switches and provides a high step up voltage gain that is suitable for very low voltage source applications, such as PV and other renewable sources. In addition, this converter allows the utilization of very low voltage stress switches and diodes. It reduces the current stress by interleaving the input current, and reduces the voltage stress by utilizing a half bridge based multiplier cell integrated configuration at the output voltage while providing high frequency galvanic isolation. The isolation is achieved through the use of 1:1 transformers which are easier to design, and the need for a high turns ratio is absent in this converter. The main theory of operation and the design guideline are presented, as is a laboratory prototype, all to validate the concept.

A High Step-Up Interleaved DC-DC Converter With Voltage Multiplier and Coupled Inductors for Renewable Energy Systems

This paper proposes a new interleaved non-isolated high step-up dc-dc converter for interfacing renewable energy applications. The proposed converter achieves a very high step-up voltage gain by using two coupled inductors and a voltage multiplier cell. This topology utilizes the interleaved boost converter in the input side, and the input current is shared with low ripple. Moreover, a voltage multiplier cell with the secondary windings of the coupled inductors is employed in the output side to achieve the interleaved energy storage. The voltage stress on the semiconductor switches and the passive components is significantly reduced and lower than the output voltage. The aforementioned converter can be operated without an extreme duty cycle or a high turns ratio. The reverse recovery problem of the diodes is mitigated, and the leakage energy is recycled. Furthermore, by implementing low-voltage-rated MOSFETs with a small ON-resistance, the conduction losses can be reduced, and the efficiency can be improved. The topology is fed by a single input voltage, and the mathematical expression is methodically explored. The operation principle of the proposed converter and the comparison between the proposed converter with other topologies are discussed. The design, parameters selection, and experimental results are thoroughly introduced. A 32 to 800 V-dc is verified and simulated by using PLECS. Consequently, a 400 W hardware prototype is verified to validate the theory and the design.

A New Soft Switching DC–DC Converter With High Voltage Gain Capability

In this article, a new high step-up dc-dc converter with zero voltage switching (ZVS) capability is presented for renewable energy applications. In order to achieve high voltage gain without extreme duty cycles or a high turns ratio, a combination of a coupled inductor and switched diode-capacitor voltage multiplier cells is used. In the presented converter, only an auxiliary winding with a diode that operates under zero current switching (ZCS) is utilized to realize ZVS for two power switches, and an active clamp circuit is utilized to reach ZVS for the other power switches. The leakage inductance of the coupled inductor controls the current falling rate of the voltage multiplier and output diodes, and also they turn-on under ZCS condition. Hence, reverse recovery losses of the diodes are reduced. The voltage stress on the power switches is low, and low voltage rating switches can be adapted to reduce the losses of their conduction. Finally, a 1-kW experimental prototype setup with 50 V input voltage and 470 V output voltage is built to verify the converter performance.

Interleaved High Step-Up Converter Integrating Coupled Inductor and Switched Capacitor for Distributed Generation Systems

A new interleaved high step-up dc-dc converter is proposed for distributed generation systems. By integrating coupled-inductor and switched-capacitor techniques, the proposed converter achieves a very high step-up voltage gain without an extreme duty cycle or a high turns ratio. Also, a very low switch voltage stress can be achieved; thus, low-voltage-rating mosfets with a small on-resistance can be used to lower the conduction loss. Moreover, thanks to the interleaved operation at the input side, the input current is shared and low current ripple is obtained. Furthermore, the zero-current-switching of the switches is realized, and the reverse recovery problem of the diodes is alleviated. In addition, the leakage energy can be recycled and an additional clamp circuit is not required. The operation principles and characteristics of the converter are discussed in detail. A prototype with 20-V input and 400-V output is developed to verify the theoretical analysis.

Bridge modular switched‐capacitor DC‐DC converter with soft switching operation and multilevel voltage‐gain range

A bridge modular switched‐capacitor (BMSC) DC‐DC converter with soft switching operation and multilevel voltage‐gain range is proposed in this article. It is mainly composed of an interleaved booster and a switched‐capacitor circuit. The symmetrical interleaved structure is applied in the interleaved booster to obtain the ripple‐free of the input current, and the interleaved pulse width modulation control scheme is employed to achieve zero‐voltage‐switching operation of all power switches. The BMSC is employed in the switched‐capacitor circuit to achieve high step‐up gain without having to use a transformer with a high turns ratio, and it can be expanded to obtain a multilevel voltage‐gain range. In addition, the zero‐current‐switching operation of rectifier diodes can be obtained when the resonant frequency is above the operating frequency of the interleaved booster. A 400‐W prototype converter was constructed with an input voltage of 25 V. The analyses are validated by the simulation and experimental results. © 2019 Institute of Electrical Engineers of Japan. Published by John Wiley &amp; Sons, Inc.

A High Voltage-Gain Bidirectional DC–DC Converter With Full-Range ZVS Using Decoupling Control Strategy

In this paper, a high voltage-gain bidirectional dc–dc converter is proposed with zero voltage switching (ZVS) and low circulating current for the interface between the energy storage system and dc microgrid bus. A current doubler is located in the low-voltage side (LVS), and a voltage doubler is located in the high-voltage side (HVS). Therefore, high voltage gain is accomplished without a transformer of the high turns ratio. The interleaved input structure is employed to reduce the current ripple and helps to achieve voltage matching (VM) on both sides of the transformer. In the view of decoupling pulsewidth modulation plus phase shift (PPS) control strategy with two control variables, the proposed topology can achieve VM and power control through the decoupling regulations of duty cycle and phase shift angle. By analyzing the resonant process during the dead time, a fixed delta is selected to generate a bias current for full-range ZVS with low circulation losses. The optimal design is given for component parameters to accomplish full-range soft switching and circulation loss reduction. An 800-W prototype of 48–60-V input and 240-V output is constructed with 30-kHz switching frequency to verify the effectiveness of the proposed converter and the associated control strategy. The accordance between the analysis and experimental results further testifies the advantages.

Analysis, Design, and Implementation of an Elastomer Generator Based Energy Harvesting Scheme

Dielectric elastomer generator (DEG) is a special variable capacitor generator used to harvest electrical energy from ambient mechanical vibrations, such as waves, building vibrations, wind, and human movement. The DEG, by virtue of its variable capacitance, converts the applied mechanical energy into electrical form. For successful energy harvesting, the DEG requires controlled charging and discharging operations. Thus, the energy harvesting circuits, used to charge and discharge the DEG, must work in tandem with the mechanical vibrations. The energy harvested during a single cycle of DEG operation increases with an increase in the DEG operating voltage. Hence, energy harvesting circuits must drive the DEG at high voltage levels. These two requirements make the energy harvesting circuit design a challenging job. In this paper, a novel energy harvesting system is proposed to drive the DEG without needing a position sensor, a high-voltage source, or a high turns ratio transformer. The theory of the proposed scheme is explained and validated with experiments performed on a prototype DEG. The control implemented leads to a special intermittent operation of the energy recovery circuit, which is also introduced. 2.597 mJ energy was harvested from a single elastomer film of 10 cm diameter with 2.3 nF capacitance in relaxed condition.

An Interleaved Soft Switching High Step-Up Converter With Low Input Current Ripple and High Efficiency

This paper proposes a high step-up low-ripple dc-dc converter for sustainable energy conversion. A high step-up voltage gain is obtained with an input-current doubler and a switched-capacitor circuit rather than having to use a transformer with a high turn ratio. A low input current ripple is achieved since the current ripples of two input inductors cancel each other out when the primary-side branches work in an interleaving way. A low output voltage ripple is got by charging and discharging complementarily with each other of two output capacitors. In addition, the proposed converter achieves zero-voltage switching (ZVS) for all power switches and zero-current switching (ZCS) for all rectifier diodes, which reduces the switching loss significantly. Moreover, an active-clamp capacitor is installed on the input-current doubler to suppress the voltage spike across the switches. A 400-W prototype converter was realized to demonstrate the above-mentioned performance.

A &lt;italic&gt;Ka&lt;/italic&gt;-Band Transformer-Based Doherty Power Amplifier for Multi-Gb/s Application in 90-nm CMOS

A Ka -band transformer (TF)-based Doherty power amplifier (DPA) is designed and fabricated in 90-nm CMOS process. Symmetrical Doherty structure is used to improve the 6-dB power backoff efficiency. The high turn ratio ( $N = 2$ ) current-type TF is adopted for the load modulation in a DPA to avoid from leakage power. The measured small signal gain is 19.8 dB with 3-dB bandwidth from 28.7 to 41.9 GHz. The proposed PA achieves 20.7-dBm saturated output power with above 32% power added efficiency (PAE) at 34 GHz. In the 6-dB power backoff region, the PAE of the proposed PA is about $1.7\times $ of that in a class-A PA.