Showing papers on "Inductor published in 2019"

Switched-Capacitor-Based Single-Source Cascaded H-Bridge Multilevel Inverter Featuring Boosting Ability

Abstract: Cascaded multilevel inverter (CMI) is one of the most popular multilevel inverter topologies. This topology is synthesized with some series-connected identical H-bridge cells. CMI requires several isolated dc sources which brings about some difficulties when dealing with this type of inverter. This paper addresses the problem by proposing a switched-capacitor (SC)-based CMI. The proposed topology, which is referred to as switched-capacitor single-source CMI (SCSS-CMI), makes use of some capacitors instead of the dc sources. Hence, it requires only one dc source to charge the employed capacitors. Usually, the capacitor charging process in a SC cell is companied by some current spikes which extremely harm the charging switch and the capacitor. The capacitors in SCSS-CMI are charged through a simple auxiliary circuit which eradicates the mentioned current spikes and provides zero-current switching condition for the charging switch. A computer-aid simulated model along with a laboratory-built prototype is adopted to assess the performances of SCSS-CMI, under different conditions.

High-Frequency PCB Winding Transformer With Integrated Inductors for a Bi-Directional Resonant Converter

Abstract: The momentum toward high power density high-efficiency power converters continues unabated. The key to reducing the size of power converters is high-frequency operation and the bottleneck is the magnetic components. With the emerging widebandgap devices, the switching frequency of power converters increases significantly, to hundreds of kilohertz, which provides us the opportunity to adopt printed circuit board (PCB) winding planar magnetics. Compared with the conventional litz-wire-based magnetics, planar magnetics can not only effectively reduce the converter size, but also offer improved reliability through automated manufacturing process with repeatable parasitics. Another way to reduce the number of magnetic components and shrink the size of power converters is through the magnetic integration. In this paper, a novel PCB winding based magnetic structure is proposed to integrate both inductor and transformer into one component. In this structure, the inductor value can be easily controlled by changing the cross-sectional area of the core or the length of the air gap. A 6.6-kW 500-kHz CLLC resonant converter prototype with 98% efficiency and 130-W/in3 (8 kW/L) power density is built to verify the feasibility of the proposed PCB winding based magnetic structure.

A Single Switch Quadratic Boost High Step Up DC–DC Converter

Abstract: In this paper, a high step up converter consisting of an integrated quadratic-boost converter and a voltage doubler is proposed. The integration of the quadratic-boost converter makes the system easier to lift up its voltage gain through slightly increasing the duty ratio of the single switch. The voltage doubler further increases the voltage gain of the system as the turn ratio rises. The voltage stresses on the switch and the diodes are decreased for such cascaded topology. Different operation modes are analyzed and mathematical analysis of the converter is presented in detail. The leakage inductance contributes to realizing zero current switching of the diodes in the second boost stage and the doubler and the energy can be recycled to the load. A 38-W prototype is built to work as a vehicle LED driver. Experiments are conducted to verify the advantages of the proposed converter and the efficiency is 90% at the nominal operating point.

Analysis and Design of High-Efficiency Hybrid High Step-Up DC–DC Converter for Distributed PV Generation Systems

Abstract: High step-up converters are required for distributed photovoltaic generation systems, due to the low voltage of the photovoltaic source. In this paper, a new hybrid high voltage gain dc–dc converter is created by merging the standard boost converter with a coupled inductor and different switched-capacitor techniques. With a single switch and no requirement of higher duty cycle values, the proposed converter achieves a high voltage gain and high efficiency, in addition to lowered voltage and current stresses of the components. A 200-W prototype was implemented experimentally to evaluate the converter, which reached a maximum efficiency of 97.6%.

Robust Circuit Parameters Design for the CLLC-Type DC Transformer in the Hybrid AC–DC Microgrid

Abstract: CLLC-type dc transformer (CLLC-DCT) is very popular in the hybrid ac–dc microgrid thanks to its high-power density advantage and good bidirectional power transfer capacity. In the hybrid ac/dc microgrid, the open-loop control is always utilized by the CLLC-DCT to cooperate with the bidirectional interlinking converter to realize the power and voltage conversion between the ac and dc bus. This paper first studies the circuit parameters design of the open-loop controlled CLLC-DCT with consideration of such a realistic problem: The real inductors/capacitors values are actually different with their theoretically designed values due to the operation power and temperature variation. To solve this problem, a robust circuit parameters design scheme is proposed for the CLLC-DCT in this paper. With the proposed scheme, the designed CLLC-DCT exhibits good power transmission and voltage regulation ability in the hybrid ac/dc microgrid even when its actual inductors/capacitors values vary with the practical power and temperature. The robust design method is experimentally verified in a hybrid ac/dc microgrid prototype.

An Integrated Step-Up Inverter Without Transformer and Leakage Current for Grid-Connected Photovoltaic System

Abstract: In this paper, an integrated step-up inverter without transformer is investigated for photovoltaic (PV) power generation. The proposed topology can be derived by combining a traditional boost converter with a single-phase full bridge dc–ac converter. The main features of the integrated inverter are: First, the leakage current caused by the solar cell array-to-ground parasitic capacitance can be theoretically reduced to zero due to the characteristics of the converter configuration, which can improve the efficiency and the reliability of the PV generation system; second, the output ac voltage of the proposed inverter can be higher than the input dc voltage, which is capable of connecting low voltage PV panels to the grid; third, only five active switches are used in the presented inverter, and those switching devices can be synchronously driven by various sinusoidal pulsewidth modulation methods based on the carrier; therefore, the proposed inverter is compact and with curtailed cost. The working principle and analysis of the proposed integrated inverter are elaborated. Finally, simulation and experimental results are obtained in a lab prototype, which agree well with the theoretical analysis.

Lifetime Estimation of DC-Link Capacitors in Adjustable Speed Drives Under Grid Voltage Unbalances

Abstract: Electrolytic capacitor with a dc-side inductor is a typical dc-link filtering configuration in grid-connected diode rectified adjustable speed drives (ASDs). The criteria to size the dc-link filter are mainly from the aspects of stability and power quality. Nevertheless, the reliability of the dc-link filter is also an essential performance factor to be considered, which depends on both the component inherent capability and the operational conditions (e.g., electrothermal stresses) in the field operation. Nowadays, unbalanced voltage has the most frequent occurrence in many distribution networks. It brings more electrical-thermal stress to the component, affecting the reliability of the capacitors. In order to study the reliability performance of the LC filter in an ASD system quantitatively, this paper proposes a mission profile based reliability evaluation method for capacitors. Different from the conventional lifetime estimation, a nonlinear accumulated damage model is proposed for the long-term estimation, considering the nonlinear process of equivalent series resistor growth and capacitance reduction during the degradation. Based on the proposed lifetime estimation procedure, four case studies are investigated: first, lifetime benchmarking of capacitors in LC filtering and slim capacitor filtering configurations; second, scalability analysis for the lifetime of capacitors in terms of system power rating and grid-unbalanced levels; third, lifetime estimation of capacitors in the dc-link filter with long-term mission profile; and fourth, the impact of the capacitor sizing on the lifetime of the dc-link capacitor under grid-balanced and grid-unbalanced conditions. The results serve as a guideline for proper selection of dc-link configurations and parameters to fulfill a specification in ASDs.

A New DC–DC Converter for Photovoltaic Systems: Coupled-Inductors Combined Cuk-SEPIC Converter

Abstract: An enhanced DC–DC converter is proposed in this paper, based on the combination of the Cuk and SEPIC converters, which is well-suited for solar photovoltaic (PV) applications. The converter uses only one switch (which is ground-referenced, so simple gate drive circuitry may be used), yet provides dual outputs in the form of a bipolar DC bus. The bipolar output from the DC–DC converter is able to send power to the grid via any inverter with a unipolar or bipolar DC input, and leakage currents can be eliminated if the latter type is used without using lossy DC capacitors in the load current loop. The proposed converter uses integrated magnetics cores to couple the input and output inductors, which significantly reduces the input current ripple and hence greatly improves the power extracted from the solar PV system. The design methodology along with simulation, experimental waveforms, and efficiency measurements of a 4-kW DC–DC converter are presented to prove the concept of the proposed converter. Furthermore, a 1-kW inverter is also developed to demonstrate the converter's grid-connection potential.

20-kW Zero-Voltage-Switching SiC- mosfet Grid Inverter With 300 kHz Switching Frequency

Abstract: Although SiC- mosfet has significant advantages on switching performance over traditional Si-IGBT, the switching loss of SiC- mosfet devices at hard switching rises quickly with the increment in the switching frequency. This has narrowed down further possibilities of improving efficiency and power density of the grid inverter. Zero-voltage-switching (ZVS) space-vector-modulation (SVM) technique is introduced to further push the power density of SiC- mosfet inverter. This paper focuses on the impact of applying the ZVS-SVM to three-phase two-level SiC- mosfet inverter. With the same efficiency requirement the ZVS-SVM SiC inverter can operate at a much higher switching frequency, which gives the opportunity to further reduce the size of passive components. The loss distributions, conversion efficiencies, and volumes of passive components of both a 20-kW SiC- mosfet hard-switching inverter and a 20-kW SiC- mosfet ZVS-SVM inverter have been compared under switching-frequency range from 50 to 300 kHz. Meanwhile, a new metric called “efficiency stiffness” is proposed to compare different inverters with respect to the efficiency performance against switching-frequency characteristics. In addition, high voltage overshoot of SiC- mosfet and high thermal stress of resonant inductor are the two critical issues in the SiC- mosfet ZVS-SVM inverter with high switching frequency. A power module including seven SiC- mosfet bare dies with low stray inductance is designed for ZVS-SVM inverter instead of the existing seven discrete TO-247 package SiC- mosfet s to reduce the voltage overshoots on the switches. Besides, to reduce the power loss of the resonant inductor caused by large amplitude of current at hundreds of kHz excitation frequency, design of the inductor with distributed air gap and optimal winding thickness are studied. A 20-kW SiC- mosfet ZVS-SVM grid inverter prototype is built to verify the proposed design.

A Novel High Voltage Gain Noncoupled Inductor SEPIC Converter

Abstract: In this paper, a novel noncoupled inductor high voltage gain single-ended primary-inductor converter (SEPIC) is presented. The proposed converter has various advantages, such as lower voltage stress on the switches, noninverting output voltage, high efficiency, and high voltage gain. Also, the introduced converter has a continuous input current which makes it suitable for renewable energy and fuel cell applications. Moreover, high voltage gain is achieved without using any transformer and coupled inductor, thus there is not any voltage overshoot for the switches during the turn- off process. This effect allows low conduction losses by using lower voltage rating switches and also additional clamping circuit is not needed. The control system of the presented converter is simple and the converter can be easily controlled in continuous conduction mode mode operation. Because, the gating pulses for both of the switches are the same and wide output voltage range is achieved only by changing the duty cycle. Furthermore, the number of the components compared to the other noncoupled inductor, SEPIC-based converters which provide near voltage gain to the proposed converter, is reduced. The detailed operation of the introduced converter and design considerations are discussed. Experimental results are presented to verify the performance of the proposed dc–dc converter.

High-Frequency Three-Phase Interleaved LLC Resonant Converter With GaN Devices and Integrated Planar Magnetics

Abstract: The LLC converter is deemed the most widely used topology as dc/dc converter in server and telecom applications. To increase the output power and reduce the input and output current ripples, three-phase interleaved LLC converter is becoming more and more popular. It has been demonstrated that three interleaved LLC converter can achieve further efficiency improvement at the 3-kW power level. However, the magnetic components for multiphase LLC converter are complex, bulky, and difficult to manufacture in a cost-effective manner. In this paper, a high-frequency gallium nitride (GaN)-based three-phase LLC converter is employed to address these aforementioned challenges. With GaN operating at 1 MHz, all magnetic components, namely, three inductors and three transformers, can be integrated into one common structure while all magnetic windings implemented in a compact four-layer PCB with 3-oz copper. The proposed structure can be easily manufactured cost-effectively in high quality. Furthermore, shielding techniques for full-bridge secondary have been investigated, and additional two-layer shielding has been integrated to reduce common-mode noise. A 1-MHz 3-kW 400 V/48 V three-phase LLC converter is demonstrated, and the peak efficiency of 97.7% and power density of 600 W/in3 (37 kW/L) are achieved.

99.1% Efficient 10 kV SiC-Based Medium-Voltage ZVS Bidirectional Single-Phase PFC AC/DC Stage

Abstract: Due to their extremely high energy demand, data centers are directly supplied from a medium-voltage (MV) grid. However, a significant part of this energy is dissipated in the power supply chain since the MV is reduced step-by-step through multiple power conversion stages down to the chip-voltage level. In order to increase the efficiency of the power supply chain, the number of conversion stages must be substantially reduced. In this context, solid-state transformers (SSTs) are considered as a possible solution, as they could directly interface the MV AC grid to a 400 V DC bus, whereby server racks with a power consumption of several tens of kilowatts could be directly supplied from an individual SST. With a focus on the lowest system complexity, the SST, ideally, should be built as simple two-stage system consisting of an MV AC/DC power factor correction (PFC) rectifier stage followed by an isolated DC/DC converter. Accordingly, this paper focuses on the design and realization of a 25 kW, 3.8 kV single-phase AC to 7 kV DC PFC rectifier unit based on the 10 kV SiC MOSFETs. By simply adding an $LC$ circuit between the switch nodes of the well-known full-bridge-based pulse width modulated AC/DC rectifier, the integrated triangular current-mode concept is implemented, which only internally superimposes a large triangular current ripple on the AC mains current and, therefore, enables zero-voltage switching over the entire AC mains period. Special attention is paid to the realization of the MV inductors and their electrical insulation, the AC-input $LCL$ filter to limit electromagnetic interference emissions, and the challenges arising due to cable resonances when connecting the SST to the MV grid via an MV cable. Despite the large insulation distances required for MV, the realized 25 kW MV PFC rectifier achieves an unprecedented power density of 3.28 kW/L (54 W/ $\mathrm {in}^{3}$ ) and a full-load efficiency of 99.1%, determined using a calorimetric measurement setup, which is discussed in detail in the Appendix.

Quadratic Boost DC–DC Converter With High Voltage Gain and Reduced Voltage Stresses

Abstract: This paper proposes a quadratic boost dc–dc converter with a high voltage gain and reduced voltage stresses. The conventional quadratic boost converter has a limited voltage gain, which is not suitable for high-step-up applications with various microgrids. In the proposed converter, to improve the voltage gain beyond that of a quadratic converter, a coupled inductor is adopted. Additionally, passive clamping circuits are applied to reduce the high voltage stresses caused by leakage inductance of the coupled inductor. Hence, additional power losses from the snubber circuit do not occur, and low-voltage-rating switching devices can be utilized for the main switch and output diode. Moreover, the reverse-recovery problem of the output diode can be alleviated by the leakage inductance. Therefore, the total power efficiency is improved. The theoretical analysis of the proposed converter is verified with a 300-V, 120-W prototype.

Switched Z-Source/Quasi-Z-Source DC-DC Converters With Reduced Passive Components for Photovoltaic Systems

Abstract: In this paper, switched Z-source/quasi-Z-source dc-dc converters (SZSC/SQZSCs) are proposed for the photovoltaic (PV) grid-connected power system, where the high step-up dc-dc converters are required to boost the low voltage to high voltage. The boost factor is increased by adding another one switch and diode to the output terminals of traditional Z-source/quasi-Z-source dc-dc converters. Not only does the output capacitor function as the filter capacitor; it is also connected in series into the inductors' charging loops when both switches are turned on. Compared with existing Z-source based structures, higher boost factor is realized through a small duty cycle (smaller than 0.25). On the one hand, the instability caused by the saturation of the inductors can be avoided. On the other hand, a larger range can be reserved for the modulation index of the backend H-bridge when they are used for the dc-ac conversion. Moreover, much fewer passive components are employed when compared with the recently proposed hybrid 3-Z-network topologies that have the same voltage gain, which can enhance the power density and decrease the cost. The performances of the proposed converters, including their operational principles in continuous and discontinuous current modes, voltage and current parameters of components, and impacts of parasitic parameters, are analyzed. The simulation and experimental results are given to verify the aforementioned characteristics and theoretical analysis.

High Gain Transformer-Less Double-Duty-Triple-Mode DC/DC Converter for DC Microgrid

Abstract: High-gain DC/DC converters with high efficiency are needed in dc microgrid owed to the low voltage of power sources, e.g., photovoltaic-cell and fuel-cell. This paper proposed a new high-gain double-duty-triple-mode (DDTM) converter for dc-microgrid applications. The proposed DDTM converter operates in three modes to achieve higher voltage gain without utilizing transformer, coupled inductor, voltage multiplier, and multiple voltage lifting techniques, e.g., triple, quadruple voltage lift. The modes of operation of the converter are controlled through three switches with two distinct duty ratios (double duty) to achieve wide range duty ratio. The operating principle, voltage gain analysis, and efficiency analysis of the proposed converter are discussed in detail and to show its benefits comparison is provided with the existing high-gain converters. The boundary operating condition for continuous conduction mode (CCM) and discontinuous conduction mode (DCM) is presented. The prototype of the proposed converters with 500-W power is implemented in the laboratory and experimentally investigated, which validate the performance and feasibility of the proposed converter. Due to double duty control, the proposed converter can be controlled in different ways and the thorough discussion on controlling of the converter is provided as a future scope.

An Interleaved High Step-Up Converter With Coupled Inductor and Built-In Transformer Voltage Multiplier Cell Techniques

Abstract: This paper presents an interleaved converter that benefits the coupled inductor and built-in transformer voltage multiplier cell (VMC). Compared with the other converters with only a built-in transformer or only a coupled inductor, the combination of these techniques gives an extra degree of freedom to increase the voltage gain. The VMC is composed of the windings of the built-in transformer and coupled inductors, capacitors, and diodes. The voltage stress of MOSFETs is clamped at low values and can be controlled via the turns ratio of the built-in transformer and coupled inductor that increases the design flexibility. Moreover, the energy of the leakage inductances, is recycled to the clamp capacitors which avoids high voltage spikes across MOSFETs. In addition, the current falling rate of the diodes is controlled by the leakage inductances, and the reverse current recovery problem is alleviated. Meanwhile, due to the interleaved structure of the proposed converter, the input current ripple is minimized and the current stress of the power devices is decreased. All of these factors improve the efficiency of the proposed converter in high-current and high-voltage applications. The principle operation and steady-state analysis is given to explore the advantages of the proposed converter. Finally, a 1.3-kW prototype with 50–600 V voltage conversion is built to demonstrate the effectiveness of the proposed converter.

Extended Topology for a Boost DC–DC Converter

Abstract: In this paper, a new structure for a nonisolated boost dc–dc converter is proposed. The proposed converter generates higher voltage gain than some conventional nonisolated boost dc–dc converters. In this paper, the voltage and current equations of the elements and voltage gain in continuous conduction mode and discontinuous conduction mode are extracted. Then, the critical inductance converter is extracted and the current stresses in the switches are calculated. To achieve high voltage gain, a generalized structure based on the proposed structure generates for dc–dc converters. Meanwhile, the root mean square current relations of devices are obtained for an extended structure. Finally, the results of PSCAD/EMTDC software and laboratory prototype are used to reconfirm theoretical concept.

Single-Switch High Step-Up DC–DC Converter With Low and Steady Switch Voltage Stress

Abstract: In this paper, a new high voltage gain step-up dc–dc converter is proposed for interfacing renewable power generation. The configuration optimally integrates both the coupled-inductor and switched-capacitor techniques to achieve an ultra-high step-up gain of voltage conversion with low voltage stress and high efficiency. It consists of a voltage boost unit, a passive clamp circuit, and a symmetrical voltage multiplier network. The structure becomes modular and extendable without adding any extra winding for ultra-high step-up voltage gain. The proposed topology not only reduces the voltage stress on the main switch but also maintains it steady for the entire duty cycle range. Furthermore, the reverse recovery issue of the diodes is alleviated through the leakage inductance of the coupled inductor. The operation principle and steady-state analysis are presented in detail. Experimental evaluation validates the claimed advantages and demonstrates a well-distributed efficiency curve and the peak of 96.70%.

High-Voltage-Gain DC–DC Step-Up Converter With Bifold Dickson Voltage Multiplier Cells

Abstract: This paper presents an interleaved boost converter with a bifold Dickson voltage multiplier suitable for interfacing low-voltage renewable energy sources to high-voltage distribution buses and other applications that require a high-voltage-gain conversion ratio. The proposed converter was constructed from two stages: an interleaved boost stage, which contains two inductors operated by two low-side active switches, and a voltage multiplier cell (VMC) stage, which mainly consists of diodes and capacitors to increase the overall voltage gain. The proposed converter offers a high-voltage-gain ratio with low voltage stress on the semiconductor switches as well as the passive components. This allows the selection of efficient and compact components. Moreover, the required inductance that ensures operation in the continuous conduction mode (CCM) is lower than the one in the conventional interleaved boost converter. The distinction of the proposed converter is that the inductors’ currents are equal, regardless of the number of VMCs. Equal sharing of interleaved boost-stage currents reduces the conduction loss in the active switches as well as the inductors and thus improves the overall efficiency, as the conduction power loss is a quadratic function. In this paper, the theory of operation and steady-state analysis of the proposed converter are illustrated and verified by simulation results. A $\text{200-W}$ hardware prototype was implemented to convert a $\text{20-V}$ input source to a $\text{400-V}$ dc load and validate both the theory and the simulation.

High-Frequency LLC Resonant Converter With Magnetic Shunt Integrated Planar Transformer

Abstract: Achieving high efficiency and high power density is emerging as a goal in many power electronics applications. LLC resonant converter has been proved as an excellent candidate to achieve this goal. To achieve smaller size of passive components, the resonant inductor in the LLC converter is usually integrated into the transformer by utilizing its leakage inductance. However, the leakage inductance of the transformer is usually insufficient and thus the LLC converter has to be operated in a limited frequency range (this limits the input voltage range accordingly), otherwise the power efficiency will drop dramatically. Therefore, a larger resonant inductance in the LLC converter is expected to operate in a wider input voltage range. This paper proposes a new method to create a larger resonant inductance by using a magnetic shunt integrated into planar windings. The accurate leakage inductance modeling, calculation, and optimal design guideline for LLC planar transformer, including optimal magnetic shunt selection and winding layout, are presented. A 280–380 V input and output 48 V–100 W half-bridge LLC resonant converter with 1 MHz resonant frequency is built to verify the design methodology. A comparison is made between two converters with the same parameters, one using magnetic shunt integrated transformer and the others using traditional planar transformer and external inductor. Experimental result shows the proposed converter with magnetic shunt is capable to achieve comparable high efficiency and regulation capability with the other under a wide input voltage, which verifies the optimal design methodology. Above all, this magnetics integration methodology reduces the whole converter's volume and thus increases the power density.

Design and Analysis of a Developed Multiport High Step-Up DC–DC Converter With Reduced Device Count and Normalized Peak Inverse Voltage on the Switches/Diodes

Abstract: In this paper, a developed structure is proposed for high step-up nonisolated noncoupled inductor based multiport dc–dc converters. The voltage gain per number of devices of the proposed topology is higher than that of similar topologies. This means that, by using the same number of devices, the proposed topology can generate higher gains than other structures. In other words, the proposed topology utilizes less number of devices for producing the same voltage gain, which leads to less total cost, size, weight, and complexity. Despite high voltage gain, the normalized peak inverse voltage (NPIV) on switches/diodes is low. Higher number of input ports leads to higher gains and lower NPIVs on devices. The load energy can be absorbed and stored in first input unit. Modularity, simple structure, continuous input currents, and low input current ripple are the other profits of proposed topology. Low/medium power applications are suggested for the proposed structure. Proposed topology has been explained and operational modes along with steady-state analysis have been discussed. For better verification, the proposed topology has been compared with several multiport high gain converters. Comparison results confirm the advantages of the proposed topology. Finally, the proper performance of the proposed topology has been validated by experimental results.

A Modified SEPIC-Based High Step-Up DC–DC Converter With Quasi-Resonant Operation for Renewable Energy Applications

Abstract: In this paper, a new modified single-switch single-ended primary inductor converter (MS2-SEPIC)-based high step-up dc–dc converter is presented. The proposed topology uses the coupled-inductor (CL) technique and a voltage tripler rectifier, which results in a high voltage gain for the converter. Here, the switching loss has been reduced significantly owing to the quasi-resonance operation of the circuit created by the leakage inductance of the CL along with circuit capacitors. The operational principles and steady-state analysis are discussed. Experimental results based on a 100 W laboratory prototype verify the validity of theoretical analysis.

Synchronization realization between two nonlinear circuits via an induction coil coupling

Abstract: Nonlinear chaotic circuits can be mapped into dimensionless dynamical systems by applying scale transformation. For synchronization control, linear voltage coupling via resistor has confirmed its effectiveness by applying negative feedback on the coupled circuits and nonlinear systems. In fact, resistor-based voltage coupling just bridges the electric devices of nonlinear circuits by imposing appropriate feedback current. Indeed, inductor (or induction coil) can also connect the electric devices and input appropriate stimulus feedback as induced electromotive force, and thus the coupled circuits can be regulated. In this paper, two Chua circuits are coupled by an inductor, which connects one capacitor of the coupled Chua circuits, and magnetic field coupling is activated because time-varying magnetic field and induced electromotive force are generated in the coupling inductor. For numerical approach and dynamical analysis, scale transformation is applied to get dimensionless dynamical systems under magnetic field coupling. Then the controllable parameter mapped from the coupling inductor is adjusted carefully to detect the synchronization approach. The same investigation is also carried out on the circuit platform Multisim. It is found that inductor coupling can benefit the realization of synchronization between two chaotic Chua systems. Complete synchronization can be reached between two identical circuits when the inductor coupling is activated with appropriate intensity. While phase synchronization can be stabilized between two non-identical circuits, chaotic oscillation can be suppressed by periodic Chua circuit under inductor coupling. The potential mechanism for inductor-based synchronization can be explained as magnetic field coupling, which field energy can be propagated via the coupling inductor with time-varying induced electromotive force, and it can give possible insights to know the information encoding between neurons and neural circuits.

Optimal Design of Planar Magnetic Components for a Two-Stage GaN-Based DC–DC Converter

Abstract: This paper develops a 200-W wide-input-range (64–160-to-24-V) rail grade dc–dc converter based on gallium nitride devices. A two-stage configuration is proposed. The first regulated stage is a two-phase interleaved buck converter ( $>$ 400 kHz), and the second unregulated stage is an LLC (2-MHz) dc transformer. In order to achieve high frequency and high efficiency, the critical-mode operation is applied for the buck converter, and the negative coupled inductors are used to reduce the frequency and the conduction losses. Then, a systematical methodology is proposed to optimize the planar-coupled inductors. For the unregulated LLC converter, it can always work at its most efficient point, and an analytical model is used to optimize the planar transformer. Finally, the proposed dc–dc converter, built in a quarter brick form factor, is demonstrated with a peak efficiency of 95.8% and a power density of 195 W/in $^3$ .

Phase-Shifted Full-Bridge DC–DC Converter With High Efficiency and High Power Density Using Center-Tapped Clamp Circuit for Battery Charging in Electric Vehicles

Abstract: In this paper, a phase-shifted full-bridge (PSFB) converter employing a new center-tapped clamp circuit is proposed to achieve high efficiency and high power density in electric-vehicle battery charger applications. By using a simple center-tapped clamp circuit, which consists of two diodes and one capacitor, many limitations in conventional PSFB converters are solved. The proposed center-tapped clamp circuit provides the clamping path and allows the secondary voltage stress to be clamped to the secondary-reflected input voltage. This results in a greatly reduced conduction loss in the secondary full-bridge rectifier (FBR) due to the low-forward-voltage drop of low-voltage-rated diodes, and the resistor–capacitor–diode snubber loss is eliminated. In addition, the circulating current in the primary side is removed without any duty-cycle loss. Furthermore, the turn- off switching loss in the FBR is substantially reduced due to the decreased reverse-recovery current and the reduced reverse voltage. With these advantages, high efficiency can be achieved. Besides, the size of the output inductor is considerably reduced with the aid of clamping voltage, resulting in a high power density with saving the cost. In order to confirm the effectiveness of the proposed converter, a 3.3-kW prototype was tested. Experimental results show that the proposed converter achieves high efficiency over the entire conditions with high power density.

High step-up DC–DC converter with coupled inductor suitable for renewable applications

Abstract: In this study, a new non-isolated high step-up DC-DC converter is presented with high-voltage gain which is suitable for renewable applications. The proposed converter uses coupled inductor and voltage multiplier cell (diode capacitor) for increasing the voltage level. The voltage gain of the proposed converter can be increased by selecting the appropriate turns ratio of coupled inductor. Voltage multiplier cell consists of two diodes and two capacitors which are used to obtain high-voltage gain. The diode-capacitor cell is used as a clamp circuit, which leads to reducing the voltage stress across the semiconductors. The proposed converter has a single power switch which causes the control of the proposed converter is simple. Also, the power switch is used with lower ON-state resistant ( R DS-ON ). The zero-current switching of the diode is obtained in OFF state. Therefore, the conduction losses are decreased with lower normalised voltage stress across semiconductors. To prove the performance of the proposed converter, theoretical analysis and comparison with other converters are provided. To confirm the benefits of the proposed converter, a laboratory prototype with 20 V input voltage, 200 V output voltage and about 200 W power level at operating 25 kHz is built and tested.

Synchronized Triple Bias-Flip Interface Circuit for Piezoelectric Energy Harvesting Enhancement

Abstract: The power conditioning interface circuit plays a crucial role in the energy harvesting (EH) capability enhancement in piezoelectric EH (PEH) systems. The principle of most existing synchronized switch circuits for PEH enhancement was summarized under the recently introduced synchronized multiple bias-flip (SMBF) model. The optimal bias-flip strategy derived from SMBF provides valuable insights for future circuit development. Based on such theoretical foundation, this paper implements a new interface circuit called the parallel synchronized triple bias-flip (P-S3BF) for further boosting the harvesting capability beyond the state-of-the-art solutions. By sophisticatedly allocating more bias-flip actions, it makes the best compromise between higher extracted power and lower dissipated power for power conditioning, toward maximum net harvested power. Moreover, the bias voltage reference in P-S3BF is self-contained and self-adaptive. Compared to the other existing solutions involving active voltage manipulations, these two conveniences brought in by P-S3BF are the most significant and necessary features, which facilitate the practical stand-alone implementation of P-S3BF under different periodic vibrations. Experimental result shows that, with the piezoelectric cantilever in use, which vibrates at a constant deflection magnitude, the P-S3BF circuit harvests 24.5% more power than its single bias-flip counterpart, the extensively studied parallel synchronized switch harvesting on inductor; and 287.6% more power than its null bias-flip counterpart, the standard EH bridge rectifier.

Ripple-Free Input Current High Voltage Gain DC–DC Converters With Coupled Inductors

Abstract: This paper presents three nonisolated high voltage gain dc–dc converters with ripple-free input current. The proposed converters combine coupled inductors and voltage-doubler structure (VDS) to achieve high step-up of input voltage. An active clamp circuit is used to suppress voltage spike of the switch caused by of the leakage inductor of the coupled inductor. VDS is placed in the secondary winding of the coupled inductor that clamps the diodes voltage stress. Working principle and design methodology of the proposed converters are presented in detail. Experimental results for a 300 W laboratory prototype, 48 V input voltage, and regulated output voltage of 400 V, are shown to validate the operation of proposed converters.

A High-Power-Density Power Factor Correction Front End Based on Seven-Level Flying Capacitor Multilevel Converter

Abstract: This paper presents a power factor correction (PFC) front end based on a seven-level flying capacitor multilevel (FCML) boost converter. Compared to the conventional two-level boost converter, the proposed seven-level FCML converter features the use of low-voltage-rated transistors, reduced voltage stress, and high effective switching frequency on the filter inductor. These characteristics of the FCML converter lead to drastic reduction in the filter inductor size while maintaining high efficiency and, therefore, significantly improve the power density of the PFC front end compared to conventional solutions. On the other hand, the small inductance imposes challenges on the PFC control. The dynamics of the seven-level FCML converter has been analyzed, and a feedforward control has been implemented to overcome these challenges. A hardware prototype is designed for universal ac input (90 to 265 Vac), 400-V dc output, and 1.5-kW power rating. Compared to existing solutions, the hardware prototype demonstrates improved efficiency and power density while maintaining high power factor and low THD. A power density of 219 W/in3 (490 W/in3 for the power stage) has been achieved, and a peak efficiency of 99.07% has been experimentally verified.