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ABSTRACT This paper presents a flyback converter with high efficiency and high power density. An optimal design method for high power density planar transformers is presented. Applying the principle of flux cancellation, a matrix transformer that originally needed an independent magnetic core was integrated into a single magnetic core to reduce the volume of the core. This method effectively reduces the printed circuit board (PCB) layer number of the planar transformer and increases the possibility of the application of the planar transformer in the flyback converter. An optimized design method of the winding structure is given according to that model to further reduce the winding loss of the transformer. Meanwhile, the proposed structure is verified by finite element analysis software. Finally, a multi‐output flyback converter with a frequency of 100 kHz is designed to verify the practical performance of the proposed transformer. [ABSTRACT FROM AUTHOR]

In response to the need for smaller and lighter power supply equipment, there has been a push towards higher power density in current power electronic converters. This development aligns well with the requirements of photovoltaic grid‐connected inverters. Among various passive filters utilized in these inverters, the LCL filter stands out as a popular choice. Nevertheless, it should be noted that traditional LCL filters have limited core utilization and exhibit significant redundancy. In view of the above problems, this paper proposes a magnetic integrated passive filter based on ripple transfer technology and carries out volume optimization design. Compared to the conventional LCL filter, the magnetic integrated passive filter offers a reduction in size and weight while preserving its capability to ripples attenuate. Finally, a laboratory prototype with a rated power of 2 kW is built to verify the effectiveness of the proposed magnetic integrated passive filter. [ABSTRACT FROM AUTHOR]

The LLC resonant converter used in high-power situations suffers from the problems of high conduction loss and current stress, which can be solved using input-parallel output-parallel (IPOP)-connected converter modules. However, this leads to a multiple increase in the number of magnetic components, which reduces power density. Magnetic integration technology is an effective way to reduce the volume of converters. Currently, the magnetic integrated transformer based on EE-type cores is widely used to realize miniaturization, and it uses leakage inductance instead of resonant inductance to improve power density. However, leakage inductance is difficult to control, and the external radiated magnetic field will produce serious eddy current loss and electromagnetic interference. This article proposes a novel double B-type magnetic integrated transformer, which can integrate the magnetic components of two LLC resonant converters simultaneously and where the resonant inductances are wound independently. The structure contains four low reluctance branches, which are used as the cores of the transformer and the resonant inductance. The decoupling integration method, which integrates the four components into a single core, has been used to increase core utilization and improve power density. On this basis, the transformer's high- and low-voltage windings are cross-arranged to reduce the magnetic field intensity in space, further decreasing the loss and electromagnetic interference. Compared with the EE-type magnetic integrated transformer, the volume of the proposed structure is reduced by 5.9%. A 400W experimental prototype is built, and the results verify the validity of the design. [ABSTRACT FROM AUTHOR]

The LLC resonant converter used in high-power situations suffers from the problems of high conduction loss and current stress, which can be solved using input-parallel output-parallel (IPOP)-connected converter modules. However, this leads to a multiple increase in the number of magnetic components, which reduces power density. Magnetic integration technology is an effective way to reduce the volume of converters. Currently, the magnetic integrated transformer based on EE-type cores is widely used to realize miniaturization, and it uses leakage inductance instead of resonant inductance to improve power density. However, leakage inductance is difficult to control, and the external radiated magnetic field will produce serious eddy current loss and electromagnetic interference. This article proposes a novel double B-type magnetic integrated transformer, which can integrate the magnetic components of two LLC resonant converters simultaneously and where the resonant inductances are wound independently. The structure contains four low reluctance branches, which are used as the cores of the transformer and the resonant inductance. The decoupling integration method, which integrates the four components into a single core, has been used to increase core utilization and improve power density. On this basis, the transformer's high- and low-voltage windings are cross-arranged to reduce the magnetic field intensity in space, further decreasing the loss and electromagnetic interference. Compared with the EE-type magnetic integrated transformer, the volume of the proposed structure is reduced by 5.9%. A 400W experimental prototype is built, and the results verify the validity of the design. [ABSTRACT FROM AUTHOR]

This paper proposed an input-parallel and output-series (IPOS) LLC resonant converter for applications with high voltage gain and low ripple, which considers the sharing of submodule output voltages. The resonant converter proposed has an integrated magnetics, which improves the utilization of the core. The reason is because magnetic fluxes can be superimposed or cancelled each other when the resonant currents are interleaved. Moreover, the influence of parameter mismatch in the resonant tank on voltage and current sharing in IPOS-LLC was analyzed based on the passive impedance theory. The results show that, by selecting smaller quality factors and using N-connections in high-voltage applications, the sharing of output voltage among modules can be well reflected, despite tolerances of the resonance parameters. Meanwhile, the voltage stress distribution of the rectifier diodes in each submodule is optimized, which improves the reliability of the circuit. By using the aforementioned conclusions, a prototype with 90 kHz, 40 V/4.8 kV, and 1.15 kW is established. The measured output voltage mismatch of 3.1% and voltage ripple rate of 0.16% at 3.7 nF output capacitance proves the effectiveness and correctness of the proposed resonant converter design.

A key component of the magnetic resonant chargers is the coupler, which must be connected to the compensation networks to improve the power transfer. The design of both structures are tightly related since the configuration of one affects the other. Thus, the integration of both structures is convenient to ease the development of other systems of the wireless charger such as the power converters and control. This integration can be optimized if physical aspects are considered. In this paper, we propose a novel physical integration of circular pads and a LCC-LCC compensation. If both systems are connected without any specific consideration, the inclusion of the reactive components in this high-order compensation network derives in a more bulky-structure. Our proposal consists in implementing the inductors of the compensation networks in the same structure of the power coils, leading to a compact system. The position of the compensation coils must be carefully analysed in order to minimise undesired coupling effects. In the proposed integration approach, we have analysed the coupling coefficients between the magnetic components for several positions to identify the optimised configuration. The feasibility of this compact structure has been validated in a prototype, proving that the power transfer levels are suitable. These tests have been carried out for different misalignment conditions, which could model its performance for dynamic charging.

Electric vehicles contain various types of light emitting diode (LED) devices. A significant twice-line-frequency ripple current is usually produced in a conventional offline LED driver with a high power factor. In this paper, a flicker-free LED driver based on isolated Cuk converter with integrated magnetic technique is proposed. Two inductors and power transformer are combined into one magnetic core to eliminate the wave current as much as possible. With time domain analysis in electrical circuit and magnetic circuit, the operation principle, operational waveforms, and transfer function are analyzed in detail. Finally, experimental results from a 30 W laboratory prototype supplied by a 220 V grid validate the effectiveness of proposed LED driver. [ABSTRACT FROM AUTHOR]

In this article, a power-split-based wireless charging system (WCS) with communication-free coordination control is proposed to combat wide load and coupling variations. By using a magnetic integrated inductor, two power delivery channels are created from a single receiver coil. Large portion of received energy is directly delivered to the load. Small amount of energy is converted by using a low-voltage low-power dc–dc converter to regulate the output voltage or current achieving constant voltage (CV) or constant current (CC) charging operation. This proposal achieves higher power conversion efficiency than the traditional two-stage cascaded converter WCS. Since the dc–dc converter only processes partial power of the WCS system, this proposal reduces the voltage stress of the devices and design difficulty. A communication-free coordination control is applied, which is established by sensing the input current drop caused by the burst operation of the partial-power dc–dc converter. Thus, the CC-CV charging is realized by PWM control at the receiver (Rx) side, and the inverter is regulated with subharmonics control scheme to maintain nearly constant Rx coil current. Simulation results for both high-voltage high-power scenarios and low-voltage low-power (LVLP) scenarios are provided to investigate the operation of the proposed WCS. Finally, experimental results are captured from a 250 W/60–84 V LVLP prototype to validate the feasibility and practicability of proposed concept. [ABSTRACT FROM AUTHOR]

Copyright of Electric Drive is the property of Electric Drive Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Using passive electromagnetic interference (EMI) filter to suppress the common mode (CM) noises on the dc and ac side of motor drive systems is a common filtering method. Shrinking the volume of CM inductors is the key to the miniaturization of EMI filters. In order to reduce the volume, this article proposes a new method to integrate the dc and ac CM inductors by magnetic coupling. The principle of the filter and the design constraints of coupled CM inductors are analyzed. The filter volume reduction advantage gained by using the proposed method is illustrated. A model is built to describe the relationship between the coupling coefficient and filtering performance. Finally, the procedures for design of coupled inductors are addressed and the results are verified by experiments. In the comparative case study, the volume of coupled inductor is 90% of that of discrete inductor. [ABSTRACT FROM AUTHOR]

In this article, a new resonant three-port dc–dc converter with dual half bridges plus one full bridge is proposed, which can realize bidirectional power flow between each port. The resonant capacitor has three functions in the circuit: the resonant capacitor can improve the magnetic bias of half bridge converter, and therefore, the transformer saturation can be avoided; the resonant capacitor is introduced to make the inductor current close to sine wave, so that the eddy current loss of the transformer can be reduced; by setting the resonant frequency of one of the three ports equal to the switching frequency, the mutual interference between the other two ports can be reduced, so that the hardware decoupling effect is achieved. First, the operation principle of the three-port converter is analyzed. Second, the steady-state model of the converter is established, and the power transmission characteristics and soft-switching characteristics are analyzed. Third, the cause of the power coupling between ports is analyzed and the hardware decoupling method is proposed. Finally, the number of magnetic elements is reduced through magnetic integration, and the correctness of the theoretical analysis is verified by simulation and prototype experiments. [ABSTRACT FROM AUTHOR]

This paper proposes a three-port power electronic transformer (PET) based on magnetic integration, where the modular multilevel converter (MMC) arm inductors and high-frequency transformer are integrated; thus, the low-voltage DC (LVDC) port can be directly obtained. Such a magnetic integration structure has advantages of reduction in magnetic volume and number of active switches, implying a compact structure and reduced cost. Compared with existing PETs, the proposed PET can save more than 60% of magnetic volume and more than 19% of device cost. The proposed PET is suitable for AC/DC hybrid distribution applications with medium-voltage DC (MVDC), medium-voltage AC (MVAC), and LVDC ports, especially for scenarios where moderate amounts of power (100 s of kW) are tapped from an LVDC port. The feasibility of the proposed three-port PET has been verified by simulation and experimental results. [ABSTRACT FROM AUTHOR]

The magnetic elements are the important parts of the dc–dc converters, which is the constriction to improve the power density of the systems. In this letter, a magnetic integration structure is proposed to integrate the magnetizing and leakage inductance for split transformer with standard UI cores, which are mass-produced. Compared with the EI/EE-core structure to achieve magnetic integration, the magnetic field is theoretically evenly distributed in a UI core, and the center leg is removed because of the flux cancelation during the derivation process of the proposed magnetic structure. In this magnetic integration structure, the magnetizing inductance and the leakage inductance can be controlled accurately by designing the numbers of printed circuit board (PCB) windings and the air gap length of the UI core. The derivation process of the proposed magnetic integration and mathematical analysis is studied. The step-by-step design process is investigated, and a design example is given. A 250 kHz, 800 W, 360/380 V LLC prototype is built to verify the feasibility of the proposed magnetic integration method. [ABSTRACT FROM AUTHOR]

With the development of data center, promotion for efficiency and power density of the voltage regulator module (VRM) is paid considerable attention. Isolated VRM is suitable for the high-conversion-ratio dc–dc application. However, isolated VRM has many magnetic components, which take up a large proportion of the total volume. In this article, a novel integrated matrix magnetics structure is proposed, which integrates two elemental transformers and four output inductors into a single core. By integrating several discrete magnetic components, the volume of passive components, and high-current interconnections are reduced, leading to high power density and high efficiency. The integrated matrix magnetics is employed in an isolated single-stage converter, which can provide high output current. In addition, primary switches can achieve zero-voltage-switching (ZVS), and synchronous rectifiers of secondary side can achieve ZVS and zero-current-switching, so efficiency can be further improved. Besides, equivalent output inductance, voltage conversion ratio and AP calculation are derived to design the integrated matrix magnetics. Finally, a 48 V/1.8 V 144 W prototype of the isolated single-stage converter with integrated matrix magnetics is made and tested to verify the analysis. [ABSTRACT FROM AUTHOR]

In order to solve the problem that the volume of the three-phase LLC resonant converter is relatively large and improve the power density of the converter, the topology of the three-phase Y-Y interleaved LLC resonant converter is adopted, the working principle is analyzed, and the equivalent model of the fundamental wave of the resonant network is established. Based on the principle of transformer magnetic integration, a new "Y"-shaped magnetic core structure is designed. By establishing a magnetic circuit model, the parameters of the transformer are designed. The ANSYS software is used to model and analyze the magnetic flux of the new transformer. An experimental prototype with output power of 600 W and voltage of 400 V/48 V is designed. The research results show that the designed magnetic core structure can significantly reduce the volume of the converter, improve the working efficiency, and the current sharing effect of the topology structure is better. The design of transformer parameters is reasonable. [ABSTRACT FROM AUTHOR]

Electric vehicles contain various types of light emitting diode (LED) devices. A significant twice-line-frequency ripple current is usually produced in a conventional offline LED driver with a high power factor. In this paper, a flicker-free LED driver based on isolated Cuk converter with integrated magnetic technique is proposed. Two inductors and power transformer are combined into one magnetic core to eliminate the wave current as much as possible. With time domain analysis in electrical circuit and magnetic circuit, the operation principle, operational waveforms, and transfer function are analyzed in detail. Finally, experimental results from a 30 W laboratory prototype supplied by a 220 V grid validate the effectiveness of proposed LED driver.

Output filter is an essential part of a grid-connected inverter used for improving the quality of a grid-injected current. The use of LCL filters in power converters in microgrid applications is more preferred compared with L or LC filters because of their better harmonic attenuation capability. However, LCL filter still occupies a main part of the weight and volume of the whole system. Thus, more progress can be further developed with this consideration. In this paper, based on a 2.5 kW three-phase voltage source inverter, a magnetic-integrated LCL filter is designed by sharing an EIE-type core to reduce weight and size significantly. With the magnetic coupling influence taken into consideration, more effective design principles of the filter are discussed according to theoretical analysis and mathematical modeling. Meanwhile, a double closed-loop control strategy is utilized to eliminate the resonance introduced by the LCL filter and stabilize the system. Simulation and practical experiments are conducted with a detailed comparison between the discrete and integrated LCL filters, which can verify the feasibility and validity of the proposed method. [ABSTRACT FROM AUTHOR]

High power density and high efficiency is a major trend in the development of power converters. The main measure to reduce the size of power converter is to improve the working frequency, and the limiting factor is the size of magnetic components. With the development of new semiconductor devices, the working frequency of power converters has been significantly improved, which gives us the opportunity to apply printed circuit board (PCB) winding planar magnetics. Compared with the traditional high frequency magnetics, planar magnetics not only reduce the size of the magnetic components effectively but also improve reliability through repeatable automated manufacturing, which is convenient for large-scale production. Magnetic integration is another method to reduce the size of the power converter. In this paper, a new magnetic structure based on PCB winding is proposed, which integrates inductance and transformer into one component. And the inductor can be independent of the transformer. In this structure, the inductance of inductor and excitation inductance of transformer can be easily controlled by changing the number of winding turns or the length of the air gap. A 20-W 200-kHz halfbridge LLC resonant converter with a peak efficiency of 94.9% is built to verify the feasibility of the designed planar magnetic integrated structure. [ABSTRACT FROM AUTHOR]

This paper proposes a three-port power electronic transformer (PET) based on magnetic integration, where the modular multilevel converter (MMC) arm inductors and high-frequency transformer are integrated; thus, the low-voltage DC (LVDC) port can be directly obtained. Such a magnetic integration structure has advantages of reduction in magnetic volume and number of active switches, implying a compact structure and reduced cost. Compared with existing PETs, the proposed PET can save more than 60% of magnetic volume and more than 19% of device cost. The proposed PET is suitable for AC/DC hybrid distribution applications with medium-voltage DC (MVDC), medium-voltage AC (MVAC), and LVDC ports, especially for scenarios where moderate amounts of power (100 s of kW) are tapped from an LVDC port. The feasibility of the proposed three-port PET has been verified by simulation and experimental results.

A CLL resonant converter with transformer–inductor-integrated magnetics is proposed. The CLL resonant converter is derived by placing the resonant inductor of an LLC resonant converter on the secondary side of the transformer. In comparison with an LLC resonant converter, the circulating current associated with the magnetizing current of the transformer is removed from the resonant inductor. More importantly, the phase difference between the flux in the magnetic cores of the transformer and the resonant inductor becomes larger. Therefore, the flux of the transformer and inductor can be cancelled with each other, resulting in a reduced loss and volume of the magnetic core. A novel structure is proposed to integrate the transformer and inductor with integrated winding structures. Detailed analysis and optimized design of the integrated transformer–inductor are presented. The effectiveness and feasibility of the proposed solutions are verified with simulation and experimental results. [ABSTRACT FROM AUTHOR]

In this article, a partial parallel dual active bridge (PPDAB) converter is proposed to lower the current stress over the switching devices on the low-voltage side. Gallium Nitride (GaN) transistors are used to improve efficiency and power density at 1 MHz switching frequency. Moreover, in order to reduce the number of magnetic components and achieve more compact design, with a unique three-leg core geometry, a new method of integrating three transformers and their associated interfacing inductors is proposed. The integration is able to shorten winding length and therefore reduces winding dc resistance. Moreover, wounding the secondary windings on each outer leg in the core enlarges leakage inductance, which can serve as the interfacing inductor Lac in the PPDAB converter. Given that, a reluctance model to analyze coupling effect of the secondary windings as well as their current balance is derived and validated by finite element simulations. Based on both calculations and simulations, the proposed integrated transformer is found to be functionally equivalent to three discrete transformers, in which their primary windings are connected in series, and the additional Lac inductor. Additionally, given the same number of the turns of the windings in each parallel module, the ac currents in these three secondary windings can inherently balance. Finally, a fully GaN-based 1.2-kW 1-MHz 400V/50V prototype with a peak efficiency of 97.51% is built and tested to verify the theoretical analysis. [ABSTRACT FROM AUTHOR]

Inductive power transfer (IPT) technology uses large resonant inductors as compensation components. In this article, a spatially nested magnetic integration method is proposed to integrate discrete inductors into an IPT transformer structure. Unipolar transformer coils are employed and are decoupled orthogonally from a nested solenoidal inductance coil for various misalignment cases. The variations of the coupling coefficients and the magnetic flux density distribution are presented with the three-dimensional finite-element modeling tool. An LCC series compensation circuit is selected to implement the proposed method with an optimal efficiency design. A 4-kW prototype with a 160 mm airgap is implemented to demonstrate the validity of the proposed method. The experimental results show that the compact structure retains the outstanding performance and avoids significant cross coupling for lateral, vertical, and axial misalignment. The maximum conversion efficiency of the proposed system is 96.7% at full output power and stays above 91.6% throughout the misalignment range. [ABSTRACT FROM AUTHOR]

In order to solve the problem that the output voltage of new energy power generating devices is relatively low, a high gain DC-DC converter was proposed. Boost converter and Zeta converter were combined, and then switching inductance and magnetic integration technology were introduced to obtain a high gain magnetically integrated switching inductors combination Boost-Zeta converter. The theoretical derivation and experimental verification of the converter show that the converter has the advantages of higher voltage gain and lower voltage stress. Moreover, based on the magnetic integration technology, the coupling integration scheme of three inductors was designed to reduce the inductor current ripple. Because of its good characteristics, the converter can be used in non-isolated DC boost applications. [ABSTRACT FROM AUTHOR]

A high frequency planar transformer with integrated leakage inductance and half-turn secondary windings is proposed for LLC isolated DC-DC converters. The primary windings are wound on both the center leg and the sides leg of an EI planar ferrite core to integrate the leakage inductance. With the proposed method, the magnetizing inductance is constant while adjusting the leakage inductance, thus the design of the magnetizing inductance and the leakage inductance can be decoupled. To adapt the high voltage transform ratio from 380V to 12V, the number of turns of the secondary windings is designed to be 0.5. The output voltage ripple of the LLC converter equipped with the proposed transformer is analyzed and its output filter is designed. The characteristics of the proposed transformer are simulated by ANSYS Maxwell and Simplorer. Finally, a 360V~400V input, regulated 12V output, 750W LLC resonant converter with silicon carbide (SiC) devices was built with the proposed transformer. The evaluated converter realized a power density of 23.1W/cm3 and a peak efficiency of 97% with all the auxiliary power and control circuit included.

Due to the advantages of superior harmonics attenuation ability and reduced size, the LCL filter has been widely adopted to interface between the inverter and the grid for improving the quality of injected grid currents. However, the high-order characteristics and various constraints of the LCL filter complicate the filter design. Moreover, the stability of the internal current control loop of the individual inverter is susceptible to the inherent LCL -filter resonance peak. Meanwhile, the overall system stability would be aggravated by the external interactions between the inverter and the weak grid as well as among the paralleled inverters. Both the LCL -filter resonance peak and two types of interaction would cause severely distorted grid currents. Motivated by the existing problems, a comprehensive review on the modeling and stability analysis of the LCL -type grid-connected inverters is conducted in this paper. Concretely, the generalized parameter constraints of the LCL filter are outlined to facilitate the passive components selection, and the magnetic integration techniques of filter inductors are also introduced to reduce the weight and size of filter for increasing the power density of the system. Then, the various damping methods for enhancing the individual internal stability and the relevant application issues are also discussed. Furthermore, the impedance-based method for evaluating the system-level interactive stability is subsequently reviewed, with the emphasis on different modeling methods of inverter output impedance and online impedance measurement techniques. Finally, the future research trends on the modeling and stability analysis of LCL -type grid-connected inverters are also presented.

This article proposes a magnetic integration design for EV wireless power transfer (WPT) systems, where the compensation and transmitting coils overlap one on top of the other to share the ferrite layer without any decoupling consideration. The magnetic field generated by both the compensation and transmitting coils are exploited to transfer power. To this end, a compensation method is proposed to enable magnetic field enhancement without any reactive power flow between the compensation and the transmitting coils, and to achieve input zero phase angle and constant current output. In addition, an efficient finite element analysis-based coil optimization algorithm is proposed to improve the coil misalignment tolerance on the horizontal plane, in which a reversely connected inner coil is used to stabilize the system output under misalignment conditions. Analytical and simulation results confirm transmission flux density enhancement and reduced leakage field characteristics of the proposed coil design. Finally, a scaled-down WPT prototype is built and tested to verify the performance and effectiveness of the design. The proposed design achieves 91.17% efficiency and misalignment tolerance up to 200 mm in any XY-direction while maintaining the power transfer and its efficiency. The results of this work provide insights into magnetic integration design of high-order compensation topologies featuring higher compactness, less ferrite usage, magnetic field enhancement, and misalignment tolerance for WPT systems. [ABSTRACT FROM AUTHOR]

Aiming at the excessive number of magnetic components in the PFC unit of the existing single stage AC-DC converter with high voltage input， a single-stage AC-DC converter was proposed based on boundary conduction mode Buck-Boost and LLC resonant circuits． The proposed converter is of the function of power factor correction， and it not only retains the excellent characteristics of LLC resonant circuit soft switching， but also realizes the magnetic integration， switch tube integration． Based on the detailed analysis of the working principle of the proposed converter， a 100 W prototype was built． The power factor value is 0． 974，the total harmonic distortion is 17% ，and the efficiency is 90． 6% under the rated working condition． The obtained results verify the proposed converter’s performance of excellent characteristics． [ABSTRACT FROM AUTHOR]

In this article, a high-power-density off-line light-emitting diode (LED) driver is proposed. The proposed ac–dc driver is the novel integrated buck and boost converter (IBBC). Besides the high-power-density, the converter shows a high power factor (PF), and a low total harmonic distortion (THD). The IBBC is a two-stage driver that features just one controlled switch, which leads to high PF and low THD operation ensuring high efficiency, and size and cost reduction. Moreover, the switch current is minimized as it conducts the higher of the buck or boost converter, but not the addition of both as in other integrated converters. Moreover, for a further increase of the power-density, a magnetic integration is made by integrating the two inductors of both the buck and boost converters in one core. Thus, the proposed converter has been named as fully integrated buck and boost converter (FIBBC). In this paper, the IBBC is analyzed, and a design methodology is proposed. Also, this article presents a magnetic analysis of the novel FIBBC. In addition, a comparison between two prototypes is presented, one for the IBBC and another for the FIBBC, both of them supplying an LED luminaire of 46 V/ 0.575 A. The FIBBC shows a high PF equal to 0.994, very small THD of 10%, output current ripple of 6%, and efficiency of 92.62%, which represents a landmark on the efficiency of integrated converters. [ABSTRACT FROM AUTHOR]

With the emerging technology of wide-band-gap power semiconductors and modern ferrite materials, the switching frequency of dc–dc converters can be pushed to mega-hertz range to achieve higher power density. In order to deal with a high conduction current, multiphase converters are adopted to distribute the current for both power devices and windings. However, the current unbalance among phases may cause unexpected power loss to the converters. In this letter, the current unbalance issue is addressed by an integrated current balancing transformer for a two-phase dc–dc converter. The current of two phases in the converter can be automatically compensated to be identical by the proposed structure, which also reduces the complexity of the control system. A 1-MHz GaN-based two-phase buck converter is built to verify the proposed structure and its efficiency achieves 97.5% at 4 V/6 A output with the ZVS turn-on of the switches. [ABSTRACT FROM AUTHOR]

Copyright of Electric Machines & Control / Dianji Yu Kongzhi Xuebao is the property of Electric Machines & Control and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A magnetic integration method of single- and multi-stage electromagnetic interference (EMI) filters is presented. Common-mode and differential-mode inductors are integrated into a single magnetic core unit to significantly reduce the filter volume. A 500-W silicon carbon (SiC) single-phase inverter is used as an experimental platform. The magnetic integration model is designed, and the magnetic circuit analysis is conducted in a simulation to ensure that the core will not reach magnetic saturation under full-load conditions. The feasibility of the proposed method is verified by an EMI test in a simulation and an experiment. Compared with a traditional discrete passive EMI filter, the proposed integrated EMI filters can reduce 40% of the total volume and 69% of the inductor volume in an integrated single-stage EMI filter with satisfactory EMI suppression ability. Although the weight of integrated inductor of integrated multi-stage EMI filter (IMSEF) has 23.8% increment, the IMSEF shows a better EMI suppression ability and 4.6% inductor volume reduction. [ABSTRACT FROM AUTHOR]

In this paper, a novel filter structure to suppress circulating currents is proposed based on the sequence of pulsewidth modulation voltage harmonics for high-power interleaved motor-drive systems. The sideband harmonics can be divided into positive-, negative-, and zero-sequence components. Through 120° interleaving among three paralleled inverters, a majority of positive- and negative-sequence harmonics are phase shifted. By these phase shifts, the differential-mode circulating currents between the paralleled ac–dc converters can be suppressed with the proposed filters, which have an identical structure to the three-phase common-mode chokes. Such a structure highly benefits the design and manufacturability for high-power applications where a choice of magnetic-core shapes is limited. Compared to coupled inductors (CIs) with cyclic-cascade or monolithic configurations, the number of magnetic cores can be reduced by one-third. Peak flux-linkages of the proposed filters and the conventional CIs were compared to estimate the size reduction in case of flux-limited designs. Considering the whole modulation index range, which may be required in the motor-drive systems, the maximum flux-linkage can be reduced by 50%. Prototype filters are built and showed a 33% reduction in weight and size compared to the conventional CIs. The validity of the proposed filter is verified through the simulation and a small-scale experiment. [ABSTRACT FROM AUTHOR]

With the rapid development of photovoltaic and fuel cell stacks, high voltage gain converters are urgently demanded. Conventional boost is limited by the exaggerated duty cycle, it is impossible to obtain a high voltage gain while ensuring efficiency. Therefore, a zero-voltage switching (ZVS)-modified SEPIC converter that combines a voltage multiplier cell with traditional SEPIC is proposed in this paper. With detailed parameters design process, this presented converter works at zero voltage switching (ZVS), while obtaining high voltage gain without extremely high duty cycle. Besides, voltage stress is also reduced and low-voltage component with lower parasitic parameters can be used, thus efficiency is maintained. In order to further improve the power density, an integrated inductor scheme is adopted in this paper without changing intrinsic working states of the two inductors. A 36-W prototype is built, and experiments are conducted to verify the advantages of the proposed converter. The efficiency is up to 91.5% at full load. [ABSTRACT FROM AUTHOR]

Threshold-voltage mismatch among paralleled dies leads to unbalanced turn-on peak currents and switching energies, thus degrading reliability. A passive method employing inversely coupled inductors of tens of nH and drive-source resistors reduces current unbalance. An integrated design of the coupled inductors is required to facilitate their practical use in a power module. A layout to achieve inverse coupling, high coupling coefficient, and low voltage stress, magnetic materials suitable for operation at tens of MHz, and high current rating of tens of amperes with small magnetic core are challenging for its implementation. A module with integrated coupled inductors that achieve inverse coupling by utilizing the copper trace of the substrate and bond wires, size comparable to the silicon carbide die, coupling coefficient higher than 0.98, tens of nH operating at tens of MHz, and current rating of tens of amperes was designed, fabricated, and validated in this work. The coupled inductors with magnetic material of low-temperature cofired ceramics are compatible with existing packaging technology for module fabrication. Effectiveness on reducing transient-current mismatch at various input voltages, load currents, and gate resistances was verified by experiments. Compared with the baseline module resembling commercial modules, the module with integrated coupled inductors reduces current unbalance from 36% to 6.4% and turn-on energy difference from 28% to 2.6% while maintaining the same total switching energy and negligible change of voltage stress. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

In this paper, the magnetic integration of resonant reset forward (RRF) converter and magnetic-thermal coupling analysis of integrated magnetic (IM) components are explored. The formulas of magnetic reluctance, winding turns, and magnetic flux density are obtained based on the equivalent magnetic circuit and minimum current pulsation scheme. Meanwhile, circuit-field coupling model of RRF converter and magnetic-thermal coupling model of IM components are built with the finite-element analysis (FEA) method. The simulation results illustrate that the core of the integrated RRF converter works in an unsaturated condition, the temperature rise of IM components is about 20 °C, and the integrated RRF converter has almost the same power efficiency as the conventional discrete RRF converter. Furthermore, hardware prototypes are fabricated and tested to verify the simulation accuracy and design validity. The conclusion of this paper will provide a reference for improving magnetic integration efficiency in the future design of RRF converter. [ABSTRACT FROM AUTHOR]

With the technological advancement of magnetic materials and semiconductor devices, the use of high-frequency magnetic link made of high-saturation induction and low specific core loss nanocrystalline alloy has been gaining popularity to replace the common dc link or ac link specially in integrating multiple renewable sources to the grid. The magnetic integration of multiple renewable sources through a common magnetic link has a number of advantages including galvanic isolation compared with the common dc or ac link. However, the magnetic response of the common magnetic link under multi-input excitations highly affects the energy conversion efficiency. To the best of the authors’ knowledge, the magnetic response of an advanced magnetic-material-based magnetic link under multi-input excitations has not been well investigated in the literature. In this paper, a systematic investigation is carried out to interconnect multiple sources through a common magnetic link. The magnetic response and the procedure used in the investigation are also presented and discussed in this paper. [ABSTRACT FROM AUTHOR]

In this paper, an integrated structure of coupled inductors is proposed for three-phase ac–dc power conversion. According to the differential-mode and common-mode, three coupled inductors are integrated into two inductors; one for suppressing only differential-mode circulating current, the other only for common-mode circulating current. With a series connection, two proposed inductors can be designed to replace the three coupled inductors with an identical impedance and smaller size. The proposed inductors can easily be built with standard shape cores which gives a large advantage on design for manufacturability. Analytic solutions of the maximum magnetic flux for the proposed inductors are derived for space vector PWM (SVPWM) and discontinuous PWM (DPWM)60° to estimate possible size-reduction in flux-limited designs. The solutions show that maximum volt-seconds is reduced by 33% for whole modulation index range in the DPWM60° case and a high modulation index range for the SVPWM case. A simple design guideline to replace the conventional coupled inductors is provided. The validity of the proposed integration is verified by circuit simulation and finite element analysis. A prototype design shows that the total weight and volume of the coupled inductors could be reduced by 20%. The proposed integration has been verified by an experiment with 1 kW paralleled three-phase converters. [ABSTRACT FROM AUTHOR]

For a current-fed dual-active-bridge bidirectional dc–dc converter, an extended duty cycle control is proposed. The low-voltage-side (LVS) bottom switch duty cycle can operate lower than 50%. The conduction loss of switches can be reduced by using low-voltage-ratingmosfets for the LVS. Meanwhile, a voltage mismatching control with adaptive clamp voltage regulation is proposed to achieve zero-voltage switching for all switches throughout full load range. Besides, for LVS dc inductors, a magnetic-integrated technique is used to reduce core loss, and power density can be improved by the use of only one core. The effectiveness of the proposed control is verified by the experimental results of a 1-kW laboratory prototype. [ABSTRACT FROM AUTHOR]

This paper proposes the magnetic integration techniques for two-stage high power factor dimmable electronic ballasts. To confirm that the proposed magnetic integration circuits do not degrade the normal operating performances in terms of noise reduction performances and power factor improvements, three prototypes are implemented and tested with the same designing conditions. From the experimental results, it can be concluded that the electronic ballast with integrated magnetic cores of a buck inductor and a resonant inductor using single set of "EI" magnetic core, where a CM choke uses separate single "EI" magnetic core, provides a good agreement in terms of noise reduction performances and power factor improvements comparing with that of the conventional electronic ballast where all magnetic components use three sets of "EI" magnetic cores separately. Thus, by comparing between the proposed circuit and traditional one, it can be seen that one set of "EI" magnetic core can be eliminated without any degradations of the operating performances. [ABSTRACT FROM AUTHOR]

In this study, an optimization procedure was proposed for the magnetic component of an integrated transformer applied in a center-tap phase-shifted full-bridge converter. To accommodate high power–density 0demand, a transformer and an output inductor were integrated into a magnetic component to reduce the volume of the magnetic material and the primary and secondary windings of the transformer were wound on the magnetic legs to reduce conduction loss attributable to the alternating-current resistor. With a focus on the integrated transformer applied in a phase-shifted full-bridge converter, circuit operation in each time interval was analyzed, and a design procedure was established for the integrated magnetic component. In addition, the manner in which output inductance was affected by the mutual inductance between the transformer and the output inductor in the integrated transformer during various operation intervals was discussed and, to minimize circuit loss, a design optimization procedure for the magnetic core was proposed. Finally, the integrated transformer was applied in a phase-shifted full-bridge converter to achieve an input voltage of 400 V, an output voltage of 12 V, output power of 1.7 kW, an output frequency of 80 kHz, and a maximum conversion efficiency of 96.7%.

This paper presents an interleaved current-driven phase-shift full-bridge converter for plug-in hybrid electric vehicle (PHEV) applications. In the proposed converter, soft switching of the active switches can be realized for a wide range of operating conditions by using a simple auxiliary circuit. Due to the current-driven nature of secondary rectifiers, the proposed converter is able to eliminate the voltage spikes across the output diodes and provides smooth commutations for the secondary rectifiers. Thus, diodes with lower breakdown voltage rate and lower forward voltage drop can be used to further improve the efficiency. All the passive magnetic components are integrated into the main transformer. The numbers of the output diodes are minimized because of the voltage doubler rectifier configuration. The input filtering requirements, as well as the current stresses of the switch devices, are also significantly reduced owing to the interleaving approach. Therefore, the proposed converter would be a good candidate for PHEV applications. The steady-state operation and relevant analysis results of the proposed converter are presented. Experimental results obtained from a 2-kW prototype with a peak efficiency of 97.4% validate feasibility of the proposed converter. [ABSTRACT FROM AUTHOR]