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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.

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]

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]

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]

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]

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]

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]

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 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]

This paper presents an integrated power module with the features of high power density and high efficiency. A multifunctional integrated magnetic component is designed. The component has the roles of both the filter inductor and the package of the converter. With the assist of finite-element analysis, the design and optimization of the proposed inductor are demonstrated. It has higher inductance value than the inductor used in conventional designs. The package is composed of bigger copper winding and higher thermal conductive magnetic material, leading to lower direct current resistance and better thermal performances than conventional transfer molding packaging. Benefiting from these advantages, the power module built based on the inductor can achieve higher efficiency and lower temperature rise than those based on traditional plastic packaging solution. Design of the inductor is demonstrated through the combination of analytical and simulation methods. An inductor prototype is built and used in an integrated power module to do experimental tests. Loss breakdown of the module is analyzed. The performances of the proposed power module are better than the conventional transfer molding packaging solution with the same board or other state-of-art products. [ABSTRACT FROM AUTHOR]

Magnetically integrating converter-side and grid-side inductors is an effective way to reduce the volume and weight of LCL filters. However, the inevitable magnetic coupling between the two coils weakens the high order harmonic attenuation ability of LCL filters. In this paper, an active magnetic decoupling method is proposed to tackle this issue, and the basic operation principle is to counteract the coupling inductor in the filter capacitor branch by constructing a decoupling inductor. A step-by-step design guidance of integrated LCL filters with the proposed magnetic decoupling method is presented in detail, and it is also found that a further volume reduction of magnetic cores can be achieved compared to the existing passive decoupling method. Experimental results finally verify the effectiveness of the proposed method. [ABSTRACT FROM PUBLISHER]

In this paper, an integrated transformer is proposed to provide current sensing in the primary side and passive current phase detection for a self-oscillating contactless resonant converter (SOCRC). The proposed transformer integrates power transfer and current sensing. By using the secondary current phase of a series/series-compensated resonant converter in the control of the inverter, better output controllability, dynamic response, and self-adaptability can be achieved simultaneously. The integrated current sensing winding, being a crucial part of SOCRC, is analyzed in detail. In order to make the output voltage insensitive to the clearance and misalignment conditions, the requirement of the new integrated transformer is given. Experimental results of an 80-W SOCRC prototype verify the analytical results. [ABSTRACT FROM AUTHOR]

The magnetic component is considered one of the major factors that dominate the power density of power converters. In this paper, magnetic integration of inductors of a three-phase LCL filter on delta-yoke composite core is explored and investigated. Using the conventional rectangular core as the baseline design reference, the proposed delta-yoke core achieved a weight reduction of close to 10% without affecting the filter's performance. The inductances based on both shapes were calculated and verified through magnetic circuit analysis and three dimensional finite element analysis simulation. Hardware prototypes of the integrated inductor with both the conventional rectangular and the proposed delta-yoke cores were fabricated and tested with a three-phase inverter circuit to verify the design validity. [ABSTRACT FROM AUTHOR]

As an essential part in a power converter, the magnetic cores and their design play an important role in achieving high efficiency and high power density. Accurate measurement of the core loss is important to their optimization. To improve the measurement accuracy (especially at high frequencies), previous methods proposed to cancel the reactive voltage of the testing core by using a cancellation capacitor or inductor. However, the value of the cancellation component is critical, and a small variation can induce a big measurement error, so extra effort is required to fine-tune the cancellation component value, which is a very time-consuming process and makes the standardization of the measurement instrument almost impossible. This paper presents a new measurement method with a partial cancellation concept that enables accurate core loss measurement for arbitrary wave excitation without the requirement to fine-tune the cancellation component value. The proposed method is experimentally verified up to 10 MHz. [ABSTRACT FROM AUTHOR]

High-order passive filters, such as the well-known LCL filters, are normally employed in the grid-connected power conversion systems to effectively attenuate the switching frequency harmonic introduced by the modulation of power converters. Although much more compact than the conventional single-inductor L filters, such passive filters are still bulky and expensive when compared with their active counterparts, e.g., the semiconductor switches. In order to improve the system power density and reduce its cost, the magnetic integration technique has been widely adopted so that the discrete inductors of passive filters are replaced by the integrated inductor, resulting in smaller magnetic cores and, therefore, the decreased volumes of passive filters. For conventional magnetic integrated LCL filters, the converter-side inductor and the grid-side inductor are integrated together and their coupling coefficient is intentionally minimized. In this letter, this coupling coefficient is fully utilized and properly designed, and the resulting coupling effect is equivalent to inserting an additional inductor into the filter capacitor branch loop. The integrated inductor and the filter capacitor can form an integrated LLCL filter, which exhibits the advantages of both the LLCL filter and magnetic integration, e.g., enhanced harmonic attenuation, reduced filter inductances, and system volume without adding the extra trap inductor. Finally, experimental results obtained from a single-phase grid-connected voltage-source converter interfaced by the proposed integrated filter are presented to validate its effectiveness. [ABSTRACT FROM PUBLISHER]

Many high-power converter systems are often connected to the medium-voltage network using a step-up transformer. In such systems, the converter-side windings of the transformer can be configured as an open end, and multilevel voltage waveforms can be achieved by feeding these open-end windings from both ends using the two-level dual converter. An $LCL$ filter with separate converter-side inductors for each of the converter is commonly used to attenuate the undesirable harmonic frequency components in the grid current. The magnetic integration of the converter-side inductors is presented in this paper, where the flux in the common part of the magnetic core is completely canceled out. As a result, the size of the magnetic component can be significantly reduced. A multiobjective design optimization is presented, where the energy loss and the volume are optimized. The optimization process takes into account the yearly load profile and the energy loss is minimized, rather than minimizing the losses at a specific operating point. The size reduction achieved by the proposed inductor is demonstrated through a comparative evaluation. Finally, the analysis is supported through simulations and experimental results. [ABSTRACT FROM AUTHOR]

The switching cell (SC) direct pulse width modulation ac–ac converters have several advantages; in particular, they do not experience commutation issues, are not susceptible to reverse-recovery losses of body diode of switching devices, produce output waveforms of good quality, are more immune to EMI noise, and have smaller input/output current ripples. The magnetic components of the SC ac–ac converters consist of coupled inductors and a filter inductor. This paper proposes an integrated inductor which integrates all magnetic components of the SC ac–ac converters into one magnetic assembly. The leakage inductance of the proposed integrated inductor is utilized to eliminate the filter inductor in buck, boost, and buck—boost-type SC ac–ac converters. The proposed integrated inductor improves the power density and reduces cost and losses because it requires fewer magnetic cores, coils, and soldering connections. The proposed integrated inductor is especially suitable for high-current applications because it can avoid the magnetic core saturation caused by current, and can eliminate the air gap in the core. The proposed integrated inductor can realize high leakage inductance; therefore, the input and output current ripples can be reduced significantly. To verify the proposed integrated inductor, a 2.3-kW prototype inductor was built and tested. [ABSTRACT FROM AUTHOR]

A converter system for high-power applications, connected to a medium-voltage network using a step-up transformer, is presented in this paper. The converter-side winding of the transformer is configured as an open-end, and both the ends of the windings are fed from two different converter groups. Each converter group comprises of two parallel voltage-source converters (VSCs), whose carrier signals are interleaved to improve the harmonic quality of the resultant switched output voltage of that converter group. However, an additional inductive component is required to suppress the circulating current that flows between the parallel-interleaved VSCs. An integrated inductor is proposed, which suppresses the circulating current in both the converter groups. In addition, the functionality of the line filter inductor is also integrated. Flux in various parts of the integrated inductor is analyzed, and a design procedure is also described. The volume and the losses of the proposed solution are compared with that of the state-of-the-art solution. The control of the proposed converter system is also discussed. The analysis has been verified by the simulation and experimental results. [ABSTRACT FROM PUBLISHER]

Recently, novel direct pulse width modulated (PWM) ac–ac converters using coupled inductors with switching cell structure have been introduced as an alternative to the conventional ac–ac converter topology. The converters can effectively solve the commutation problem associated with the conventional direct PWM ac–ac converters. However, the two coupled inductors used in the topology make the converters less attractive for use in practical applications. This paper proposes magnetic integration of the discrete-coupled inductors in single-phase ac–ac converters. The dc offset fluxes generated by the common-mode currents are cancelled out perfectly when the windings on the common core are appropriately arranged, resulting in ac flux only. The proposed inductor shows significant improvements over discrete-coupled inductors, in that the proposed inductor does not have an air gap, it exhibits symmetrical winding currents, and it has smaller volume with large current handling capability. The proposed inductor can handle an unlimited amount of current due to the absence of core saturation caused by the current and is well suitable for high power ac–ac conversion applications. The performance evaluation and comparison of the experimental results show that the net volume of the coupled magnetic components can be reduced by more than 50% with the proposed integration scheme. [ABSTRACT FROM PUBLISHER]

This paper examines the nonlinear behavior of inserted type integrated magnetics used in linear level control converters. Due to the nonlinear behavior of the magnetics, an implementation of the insertion type magnetic integration needs to be carefully considered. The saturation of magnetics is normally not a concern in high-voltage input applications, but becomes a serious issue when designing for low-voltage input and high power applications. In this paper, the inserted type integrated magnetics has been categorized into two types according to their magnetic integration configurations. Investigation and discussion of their nonlinear behavior will be presented with the assistance of 3-D simulation results based on the finite-element method. A case study of a 350 W dc–dc converter is used throughout this paper for the ease of illustration. [ABSTRACT FROM AUTHOR]

In this paper, a high-efficiency high power density LLC resonant converter with a matrix transformer is proposed. A matrix transformer can help reduce leakage inductance and the ac resistance of windings so that the flux cancellation method can then be utilized to reduce core size and loss. Synchronous rectifier (SR) devices and output capacitors are integrated into the secondary windings to eliminate termination-related winding losses, via loss and reduce leakage inductance. A 1 MHz 390 V/12 V 1 kW LLC resonant converter prototype is built to verify the proposed structure. The efficiency can reach as high as 95.4%, and the power density of the power stage is around 830 W/in3. [ABSTRACT FROM AUTHOR]

Magnetic core loss is an important concern for power converters. As the switching frequency increases and converter size reduced, the core loss will have significant impact to the converter efficiency and temperature. Accurate evaluation is important for magnetic design and converter loss estimation. The classic two-winding method is limited to low frequencies (usually below 1 MHz) because it is sensitive to phase discrepancy. In this paper, a new method is proposed for high-frequency core loss measurement that utilizes capacitive cancellation, which is suitable for HF and VHF core loss measurement. The new method greatly reduces the sensitivity to phase discrepancy, which is the dominating error source in the conventional two-winding method. An experimental demonstration is performed at 10 MHz, and the possible errors are analyzed in detail. With the proposed method, the high-frequency core loss can be accurately measured. [ABSTRACT FROM AUTHOR]

This letter investigates the magnetic integration of the LCL filter in grid-connected inverters. By sharing an ungapped core and arranging the windings properly, the fundamental fluxes generated by the two inductors of an LCL filter cancel out mostly in the common core. Thus, the common core with low flux level can be dramatically reduced. Although the reluctance of the common core can hardly be zero, which implies an inevitable coupling between the integrated inductors, the proposed magnetic integration scheme is still attractive if the cross-section area and magnetic material of the common core are made reasonable. Experimental results from both single-phase and three-phase grid-connected inverters verify the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

A novel isolated zero-voltage-transition (ZVT) boost converter with coupled inductors is proposed in this paper to satisfy the high power, high step-up, and isolated requirements. In the proposed converter, the input-parallel configuration is adopted to share the large input current and to reduce the conduction losses, while the output-series structure is employed to double the output voltage gain. Consequently, a transformer with a low turns ratio can be applied, which makes the transformer design and optimize easily. Moreover, the active clamp circuits are employed to reduce the switch voltage stress and to recycle the energy stored in the leakage inductance. The ZVT is achieved during the whole switching transition for all the active switches, so the switching losses can be reduced greatly. Furthermore, the diode reverse-recovery problem is partly solved due to the leakage inductance. In addition, the magnetic integration technology is applied to improve the efficiency and to reduce the magnetic component size. Finally, a 48-V input 380-V output 1-kW prototype operating with 100-kHz switching frequency is built and tested to demonstrate the effectiveness of the proposed converter. [ABSTRACT FROM PUBLISHER]

The implementation of a bridgeless power factor correction (PFC) boost rectiifier with low common-mode noise is presented in this paper. The proposed implementation employs a unique multiple-winding, multicore inductor to increase the utilization of the magnetic material. The operation and performance of the circuit were verified on a 750-W, universal-line experimental prototype operating at 110 kHz. [ABSTRACT FROM AUTHOR]

A soft-switched continuous-conduction-mode boost power factor correction front-end converter with an integrated zero-voltage-switched two-switch forward second-stage converter is introduced. In the proposed approach, a single transformer is commonly used by the two stages to provide isolation of the power supply and soft switching of all semiconductor switches including a controlled di/dt turn-off rate of the boost rectifier. The performance of the proposed approach was evaluated on a 150-kHz, 430-W/12-V, universal-line range prototype converter. [ABSTRACT FROM AUTHOR]

A circuit that substantially extends the hold-up time of ac-dc power supplies is introduced. By using integrated magnetics, the power density of this hold-up time extension circuit is maximized. The performance of the proposed approach was evaluated on a universal line range 1-kW power supply. [ABSTRACT FROM AUTHOR]

This paper presents a magnetic integration approach that reduces the number of magnetic components in a power supply by integrating magnetic components in two conversion stages. Specifically, in the proposed approach, a single transformer is used to implement the continuous-conduction-mode boost power-factor-corrected (PFC) converter and the dc/dc flyback converter. The integrated boost and flyback converters offer soft switching of all semiconductor switches including a controlled di/dt turn-off rate of the boost rectifier. The performance of the proposed approach was evaluated on a 150-kHz, 450-W, universal-line range boost PFC converter with 12-V/2.2-A integrated stand-by flyback converter. [ABSTRACT FROM AUTHOR]