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New compound magnetic material based on parallel continuous ferromagnetic microwires (e.g., based on cobalt) embedded in a body made of polymeric material can potentially offer significant mechanical advantages over well-known fragile ferrite in some applications where the magnetic material has to withstand mechanical vibrations. The diameter of the magnetic microwires is minimal (3–60  $\mu$ m) compared to the rest of the dimensions (80–300 mm) and the number of microwires is in the order of 1000 s. It requires extremely fine meshes, then brute force simulation by the finite element method is not possible. In this article, a method to overcome this limitation is proposed, which is based on the substitution of the original material by a homogenous material that behaves, in a macroscopic sense, as the compound material. The physical properties of the homogeneous material are obtained in different spatial directions, due to the inherent anisotropy of the compounded magnetic component, through analytical equations. [ABSTRACT FROM AUTHOR]

This article presents a 6.78-MHz wireless power transfer (WPT) system, which is configured to automatically cancel the reactance in primary and secondary. In the WPT system, the detuning caused by the parameter variation, the implementation of the frequency control, and components tolerance will decrease a lot the system performance, especially in very low coupling (k = 0.06) and low power applications. The delivered power is sensitive to the reactance under low coupling and high-frequency conditions, accordingly, a novel self-adaptive WPT system to automatically retune the resonance is proposed. The proposed concept uses a synchronous series compensator (SSC) instead of a capacitor in series with the secondary to tune it, which can automatically cancel the reactance caused by the inductor, nonresistive load or frequency variation, hence increases the system performance in terms of delivered power and efficiency. A prototype has been built and tested experimentally to validate the feasibility of the proposed concept. A constant power of 1.8 W can be transmitted with 50% overall efficiency at a coil separation distance of 1.5 cm between the printed-circuit-board transmitter (3 × 3 cm2) and receiver (1 × 2 cm2) under wide detuning conditions, being 0.95 the ratio between distance and the equivalent diameter of receiver. [ABSTRACT FROM AUTHOR]

This article studies design guidelines to optimize the inductive coils for electric vehicles by replacing the standard compact ferrite core with a compound of polymers, nanoparticles, and tile-links of ferrite and by reviewing different aspects of the winding to improve mechanical behavior and efficiency. A system composed of the studied vehicle assembly and ground assembly from the society of automotive engineers’ recommended practice is defined. Fast three-dimensional (3-D) finite element simulations are performed by evaluating different geometric aspects of the vehicle assembly. In doing so, the variation of coupling factor and inductance related to the geometry can be observed and compared in order to analyze the performance when the amount of compact ferrite is reduced. The polymer bonded magnetic is, then, incorporated to improve the decreased magnetic behavior due to the reduction in ferrite. In previous works, the modeling of the litz-wire and polymer bonded magnetic were developed to accelerate the simulations. In this article, we include the modeling of the compact ferrite tile-links to further reduce the time consumption of these simulations. Moreover, simple two-dimensional simulations are described to study the windings’ parasitic capacitances. The design guidelines, based on fast 3-D simulations, are detailed and validated with particular prototypes. [ABSTRACT FROM AUTHOR]

In this article, a method to replace conductors, in one or multiple layers, by an equivalent layer with homogeneous current distribution is proposed to allow complex 3-D finite element simulations. This equivalent layer needs a coarser mesh, then the simulations are accelerated. The electromagnetic properties of this equivalent layer will be defined to match skin and proximity losses of actual round and Litz-wire conductors. Analytical and empirical equations to obtain these parameters will be provided and the method is validated in several inductive power transfer coils with three dimensional geometries. [ABSTRACT FROM AUTHOR]

The main standard for avionic equipment DO-160G defines a set of tests that require compliance before the employment of a device in aircraft. An important test involves the generator voltage and consequential current distortion of the three-phase load in the variable 360–800 Hz frequency grid. The main purpose of this paper is to present and analyze a systematic design methodology for three-phase boost and buck rectifiers in order to meet with the voltage distortion test requirement. For a given voltage harmonic profile, the current harmonic limits that have to be satisfied are translated into equivalent per-harmonic admittances and a profile of maximum rectifier input admittance versus frequency is obtained. The defined profile, due to normalization, is applicable to arbitrary power level with simple shifting by the base admittance governed by the converter nominal power. It is shown that for boost-type rectifiers there is a tradeoff between current controller bandwidth and input inductor size, while for the buck-type rectifiers main limitation lies in the input LC filter design used for differential electromagnetic interference filtering. The experimental results conducted on an SiC three-phase 10 kW VIENNA rectifier are tightly backing up the proposed theoretical analysis. This paper is accompanied by three videos demonstrating experimental measurement of d-axis open-loop duty cycle to inductor current transfer function, loop-gain of d-axis current controller with 3.8 kHz bandwidth and variable grid frequency 360–800 Hz operation of the converter under 0% and 10% input three-phase voltage total harmonic distortion. [ABSTRACT FROM AUTHOR]

This paper presents a new isolated single-stage pulse-width modulation rectifier system based on the recently presented Swiss rectifier topology providing the isolation by replacing a buck with a forward converter. The principle of operation and a new modulation technique which compensates the reactive power generated by the input filter at light load and maximizes the power factor are discussed. Furthermore, the analytical equations for the stress in the semiconductor devices useful for the system optimization are derived. The proposed topology and modulation technique are experimentally validated on a 3.3-kW 115 Vac to 270 Vdc prototype demonstrator. [ABSTRACT FROM AUTHOR]

This paper presents a single-stage converter for a high-bandwidth and high-efficiency envelope amplifier. In the proposed application, due to the high peak-to-average-power ratio, high bandwidth, and the power level requirements, the envelope amplifier has low efficiency. Therefore, many efforts have been made to increase the efficiency of the envelope amplifier. To achieve this improvement, the current ripple cancellation technique is applied in this paper to a synchronous buck converter to cancel the output current ripple and to decrease the switching frequency without a reduction in the large signal bandwidth, for open-loop operation and for the envelope elimination and restoration technique. The advantages of the proposed design are presented and validated experimentally. The transfer function of the output filter of the buck converter with a ripple cancellation circuit has been modeled and compared to measurements, showing a good correspondence. Experimental validation is provided at 4 MHz of switching frequency, for dc and for variable output voltage, applying a sinusoidal reference and a 64-QAM signal. Experimental validation of the efficiency improvement is provided, compared to the equivalent design of the conventional buck converter in terms of the output voltage ripple rejection ratio and large signal bandwidth. [ABSTRACT FROM AUTHOR]

This paper presents a theoretical analysis and an optimization method for envelope amplifiers. Highly efficient envelope amplifiers based on a switching converter in parallel or in series with a linear regulator are analyzed and optimized. The results of the optimization process are shown, and these two architectures are compared regarding their complexity and efficiency. The proposed optimization method is based on the knowledge of the transmitted signal type (OFDM, WCDMA…), and it can be applied to any signal type as long as the envelope probability distribution is known. Finally, it is shown that both analyzed architectures have an inherent efficiency limit. [ABSTRACT FROM AUTHOR]

All the interconnected regulated systems are prone to impedance-based interactions making them sensitive to instability and transient-performance degradation. The applied control method affects significantly the characteristics of the converter in terms of sensitivity to different impedance interactions. This paper provides for the first time the whole set of impedance-type internal parameters and the formulas according to which the interaction sensitivity can be fully explained and analyzed. The formulation given in this paper can be utilized equally either based on measured frequency responses or on predicted analytic transfer functions. Usually, the distributed dc–dc systems are constructed by using ready-made power modules without having thorough knowledge on the actual power-stage and control-system designs. As a consequence, the interaction characterization has to be based on the frequency responses measureable via the input and output terminals. A buck converter with four different control methods is experimentally characterized in frequency domain to demonstrate the effect of control method on the interaction sensitivity. The presented analytical models are used to explain the phenomena behind the changes in the interaction sensitivity. [ABSTRACT FROM AUTHOR]

This article deals with the robust control design for linear systems with input and state delays, subject to nonvanishing matched disturbances. The controller is synthesized with the Lyapunov redesign technique in two stages: first, an optimal predictor compensates the input delay of the nominal system while a quadratic performance index is minimized. Then, the robust component guarantees that the solutions are ultimately bounded. The theoretical results are experimentally validated through a dehydration process, with the controller digital implementation on an industrial programmable automation controller cDAQ-9132. [ABSTRACT FROM AUTHOR]

In this article, analysis and design of a 3.3-kW isolated single-stage three-phase buck-type rectifier for aircraft applications is presented. The operating principle and modulation method of the proposed rectifier are introduced. The advantageous zero-voltage switching (ZVS) feature in all of the switching transitions is analyzed. A comparison with the VIENNA Rectifier III is done, being different both in the phase-leg implementation and the modulation sequence. A detailed rectifier design guideline is discussed and losses estimations are provided aiming at reaching 93.7% overall efficiency, including the EMI (electromagnetic interference) filter. Simulation waveforms are presented. Finally, experimental results obtained with the designed 3.3-kW hardware demonstrator are provided. The results verify achievement of ZVS in all of the switching transitions from full load down to 50% of nominal load, while exhibiting 1.9% THD $_I$ (total harmonic distortion) and 0.9996 PF (power factor) at nominal power, ultimately showing very good agreement to the simulation results. This article is accompanied by a video demonstrating experimental operation of the proposed rectifier at nominal input voltage, output voltage, and output power. [ABSTRACT FROM AUTHOR]

Several boost-derived topologies are analyzed and compared for an aerospace application that uses a 100 V voltage bus. All these topologies have been designed and optimized considering the electrical requirements and the reduced number of space-qualified components. The comparison evaluates the power losses, mass, and dynamic response. Special attention has been paid to those topologies that may cancel the inherent right half plane zero (RHP) zero of the boost topology. Experimental results of the less common topologies are presented. [ABSTRACT FROM AUTHOR]

Switched converters are a source of electromagnetic interference (EMI) due to the hard switching and abrupt edges in the current and voltage waveforms. Multiphase converters can reduce the EMI at the source, minimizing the conducted EMI generation, without changing dramatically the normal operation of the circuit. Input filter can be greatly reduced, radiated EMI is lower, and internal EM! problems are minimized. This paper is focused on exploring multiphase converters as a topological technique to reduce conducted differential-mode EMI generation at the source, considering some nonidealities of the multiphase converter. [ABSTRACT FROM AUTHOR]

This article presents a control linearization technique for a single-phase single-stage inverter with multiple modulation strategies. The power topology is based on an flying capacitor multi-level (FCML) inverter, and the control is based on the plant inversion. The proposed technique allows decoupling the control of the input current and the output voltage, which simplifies the control in two ways: first, the control of both variables is independent and second, the controllers are independent of the modulation applied, thanks to the plant inversion. This control is implemented in an field-programmable gate array. Since the converter operates at variable frequency, two different data acquisition alternatives are explored: sampling at variable frequency (once per switching cycle) or sampling at constant frequency (higher than the switching frequency).The proposed control is validated by simulation and experimental results with a 1-kVA prototype. [ABSTRACT FROM AUTHOR]

This article analyses the fundamental aspects of the principal resonant network topologies for inductive power transfer systems. From the analytical derivation, different features, such as the variation of the coupling factor or load changes, are studied. Based on this study, a resonant series–series topology is selected, which cancels the leakage inductance. Due to the specifications, the air gap distance and its tolerance ($\pm \text{12}\%$) produce a wide variation of the coupling factor of the inductive link. Therefore, through fast three-dimensional simulations by finite elements, the inductive link is designed so that this variation is minimized. This maintains the resonance and the designed system, in turn, behaves like a voltage source regardless of power, and thus, evades the implementation of a control stage. A dc–dc converter is constructed where the distance between the primary and secondary side vary from 35 to 45 mm, and the power ranges from 0 to 5 kW. The output voltage range goes from 38 to 55 $V_{\text{DC}}$. Experimental results for the dc–dc converter report an efficiency of over 94%. [ABSTRACT FROM AUTHOR]

This paper presents an analytical model for input, output, and reverse capacitance of a normally on AlGaN/GaN high-electron mobility transistor (HEMT) with a gate field-plate structure, when the device is in the subthreshold regime. Together with the existing model for the output I–V characteristics, the proposed capacitance model provides the complete set of analytical equations that relate the physical design parameters to the electrical characteristics of the device. The model was verified by the experimental characterization of a HEMT. In comparison to the physics-based models implemented in Finite Element Analysis tools, the obtained capacitance model has substantially lower level of complexity and, therefore, it is more suitable for implementation into iterative design optimization algorithms. In order to verify the proposed model for such usage, the prototype of a high-frequency buck converter was built, using previously modeled GaN HEMT as the main switch. The hybrid analytical-behavioral power loss model of a high-frequency buck converter was implemented into Simplorer simulation tool, using the proposed physics-based model as the device description for the capacitive part. The efficiency measurements showed good agreement with the simulation results, even at 20 MHz of switching frequency in the low range of the output power. [ABSTRACT FROM AUTHOR]

Envelope tracking (ET) and envelope elimination and restoration (EER) are techniques that have gained in importance in the last decade in order to obtain highly efficient radio frequency power amplifier that transmits signals with high peak-to-average power ratio. In this study, a multilevel multiphase buck converter is presented as a solution for the envelope amplifier used in ET and EER. The presented multiphase buck converter generates multilevel voltage using “node” duty cycles and nonlinear control. In this way, the multilevel is implemented using only one simple power stage. However, the complexity of the multilevel converter implementation has been shifted from complicated power topologies to complicated digital control. Detailed discussion regarding the influence of the design parameters (switching frequency, output filter, and time resolution of the digital control) on the performance of the proposed envelope amplifier is presented. The design of the output filter is conducted fulfilling the constraints of the envelope slew rate and minimum driver pulse that can be reproduced. In the cases when these two constraints cannot be fulfilled, they may be relieved by the modified control that is presented and experimentally validated. Finally, in order to validate the concept, a prototype has been designed and integrated with a nonlinear class F amplifier. Efficiency measurements showed that by employing EER, it is possible to save up to 15% of power losses, comparing to the case when it is supplied by a constant voltage. Additionally, adjacent channel power ratio has been measured. The obtained results showed the value higher than 30 dB for signals up to 5 MHz of bandwidth, without using a predistortion technique. [ABSTRACT FROM AUTHOR]

Conventional three-phase rectifiers are controlled to achieve good power factor and low total harmonic distortion in the input. In the case of pulsating power loads, the fast dynamic response implies that the load pulses are reflected in the generator. These pulsating loads affect the lifetime operation of the generator, especially when it is not oversized (as in the case of aircraft applications). In order to smooth the power demanded from the generator, it is preferable to reduce the bandwidth of the output voltage controller for the rectifier but it affects its stability due to the fact that the right-half-plane (RHP) pole given by the negative impedance of a constant power load requires high-bandwidth control loop to compensate it. In this paper, an energy control method is proposed that utilizes the energy stored in the output capacitor of the rectifier to control the output voltage of the rectifier. In such a way, the minimum bandwidth restriction imposed by the RHP pole of the power load is eliminated and the bandwidth of the voltage loop can be defined low enough to demand smooth power from the generator. [ABSTRACT FROM PUBLISHER]

Wireless power transfer (WPT) is an emerging technology with an increasing number of potential applications to transfer power from a transmitter to a mobile receiver over a relatively large air gap. However, its widespread application is hampered due to the relatively low efficiency of current Wireless power transfer (WPT) systems. This study presents a concept to maximize the efficiency as well as to increase the amount of extractable power of a WPT system operating in nonresonant operation. The proposed method is based on actively modifying the equivalent secondary-side load impedance by controlling the phase-shift of the active rectifier and its output voltage level. The presented hardware prototype represents a complete wireless charging system, including a dc–dc converter which is used to charge a battery at the output of the system. Experimental results are shown for the proposed concept in comparison to a conventional synchronous rectification approach. The presented optimization method clearly outperforms state-of-the-art solutions in terms of efficiency and extractable power. [ABSTRACT FROM AUTHOR]

This paper introduces the $v^1$ concept that explains how by only measuring the output voltage, designers have information about almost every signal of the power stage. Following the $v^1$ concept, it is explained how to design a traditional type-III voltage-mode control to behave like a current-mode control with near time-optimal response under load transients. This study is validated in simulations and experimentally on a 300-kHz buck converter. [ABSTRACT FROM AUTHOR]

This paper presents a primary-parallel secondary-series multicore forward microinverter for photovoltaic ac-module application. The presented microinverter operates with a constant off-time boundary mode control, providing MPPT capability and unity power factor. The proposed multitransformer solution allows using low-profile unitary turns ratio transformers. Therefore, the transformers are better coupled and the overall performance of the microinverter is improved. Due to the multiphase solution, the number of devices increases but the current stress and losses per device are reduced contributing to an easier thermal management. Furthermore, the decoupling capacitor is split among the phases, contributing to a low-profile solution without electrolytic capacitors suitable to be mounted in the frame of a PV module. The proposed solution is compared to the classical parallel-interleaved approach, showing better efficiency in a wide power range and improving the weighted efficiency. [ABSTRACT FROM AUTHOR]

This study is related to the improvement of the output impedance of a multiphase buck converter with peak current mode control (PCMC) by means of introducing an additional power path, which virtually increases the output capacitance during transients. Various solutions that can be employed to improve the dynamic behavior of the converter system exist, but nearly all solutions are developed for a single-phase buck converter with voltage mode control, while in the voltage regulation module applications, due to the high currents and dynamic specifications, the system is usually implemented as a multiphase buck converter with current mode control to ensure current sharing. The proposed circuit, output impedance correction circuit (OICC), is used to inject or extract a current n – 1 times larger than the output capacitor current, thus virtually increasing n times the value of the output capacitance during the transients. Furthermore, the OICC concept is extended to a multiphase buck converter system and the proposed solution is compared with the system that has n times bigger output capacitor in terms of dynamic behavior and static and dynamic efficiency. The OICC is implemented as a synchronous buck converter with PCMC, thus reducing its penalty on the system efficiency. [ABSTRACT FROM AUTHOR]

V2Ic is a ripple-based control with an excellent performance for load transients and reference voltage tracking because it exhibits a feedforward of the load current and the error of the output voltage. However, if V2Ic is modulated with constant frequency, constant on-time or constant off-time, its dynamic response is hindered by delays in the response. This paper proposes a technique that synchronizes the clock of the converter to initialize the duty cycle when a worst-case load transient occurs using the current through the output capacitor to detect load transients. It is exemplified on a V2Ic control but it is applicable to most of controllers as it only acts on the modulator. [ABSTRACT FROM AUTHOR]

V2Ic control provides very fast dynamic performance to the Buck converter both under load steps and under voltage reference steps. However, the design of this control is complex since it is prone to subharmonic oscillations and several parameters affect the stability of the system. This paper derives and validates a very accurate modeling and stability analysis of a closed-loop V2Ic control using the Floquet theory. This allows the derivation of sensitivity analysis to design a robust converter. The proposed methodology is validated on a 5-MHz Buck converter. The work is also extended to V2 control using the same methodology, showing high accuracy and robustness. The paper also demonstrates, on the V2 control, that even a low bandwidth-linear controller can affect the stability of a ripple-based control. [ABSTRACT FROM AUTHOR]

The combination of minimum time control and multiphase converter is a favorable option for dc–dc converters in applications where output voltage variation is required, such as RF amplifiers and dynamic voltage scaling in microprocessors, due to their advantage of fast dynamic response. In this paper, an improved minimum time control approach for multiphase buck converter that is based on charge balance technique, aiming at fast output voltage transition is presented. Compared with the traditional method, the proposed control takes into account the phase delay and current ripple in each phase. Therefore, by investigating the behavior of multiphase converter during voltage transition, it resolves the problem of current unbalance after the transient, which can lead to long settling time of the output voltage. The restriction of this control is that the output voltage that the converter can provide is related to the number of the phases, because only the duty cycles at which the multiphase converter has total ripple cancellation are used in this approach. The model of the proposed control is introduced, and the design constraints of the buck converter's filter for this control are discussed. In order to prove the concept, a four-phase buck converter is implemented and the experimental results that validate the proposed control method are presented. The application of this control to RF envelope tracking is also presented in this paper. [ABSTRACT FROM AUTHOR]

In this paper, a multiphase converter where the phases are coupled by transformers is proposed to implement a minimum energy-storage converter. Advantages and drawbacks of this topology are analyzed and validated by means of three prototypes. The two main advantages of the minimum energy-storage concept are that the converter can be operated at very low frequency since the transient response is not affected by the switching frequency, thus achieving very high efficiency while at the same time, providing a fast energy transfer between the input and the output. Since this topology operates (ideally) with no energy storage, energy flow into the magnetic elements of the topology needs to be adequately controlled. The main application of this topology is a “dc–dc transformer” for two-stage power architectures. [ABSTRACT FROM AUTHOR]