Output Power Level Research Articles

Design and Fabrication of E-Band Traveling Wave Tube for High Data Rate Wireless Links

<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\textit{E}$</tex-math> </inline-formula> -band (71–76 and 81–86 GHz) is widely used for wireless point to point (PtP) links with a few gigabit/second data rate. <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\textit{E}$</tex-math> </inline-formula> -band front ends are powered by solid-state amplifiers with about 1-W output power per module. This level of output power limits range and spectral efficiency in rain condition and has to be compensated by high gain antennas or backup low-frequency links with reduced capacity. The availability of tens of watts of transmission power would allows higher spectral efficiency and long range, and the use of lower gain antennas for multibeam and area coverage. Millimeter wave traveling wave tubes (TWTs) are gaining interest due to their higher power, more than one order of magnitude, in comparison with solid-state devices. Helix TWTs, typically built at microwaves, are very arduous to fabricate due to the extremely small diameter of a helix at <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\textit{E}$</tex-math> </inline-formula> -band. This article reports the design and fabrication of the first ever <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\textit{E}$</tex-math> </inline-formula> -band TWT based on a full metal slow wave structure (SWS), the double corrugated waveguide (DCW). The TWT is designed to provide about 70-W power and more than 35-dB gain in the 71–76-GHz band. A test TWT using a single section interaction structure is in the final assembly phase as proof of concept with about 2-W output power. The <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\textit{E}$</tex-math> </inline-formula> -band TWT performance will open new perspectives in the availability of long range wireless links with multi-Gb/s data rate needed for enabling 5G and 6G new networks.

An Advanced Switched-Capacitor Multilevel Inverter Topology With a Robust PWM Controlling Technique and Voltage Boosting Property for the Grid-Connected Renewable Energy Applications

This paper proposes an improved switched-capacitor Multilevel Inverter that utilizes fewer components. The switched capacitors are employed with the DC sources in the proposed configuration to minimize the number of DC-Links in the structure, which keeps the structure compact and combinable. Those capacitors enjoy a self-charging susceptibility with the ability to balance naturally. The suggested structure supports the expansion process to catch up with satisfactory output power levels based on a slight increase in the components count. The targeted application for this inverter involves a renewable energy system (RES) to exploit the extracted electrical power and inject it into the grid. The paper suggests a developed PWM controller to control the system’s operation. The controlling scheme has the ability to adjust the balance in the DC-Links voltages to keep generating a regular output voltage. Furthermore, it helps in extracting the maximum available power from renewable resources. Meanwhile, the controller injects the real power component into the grid, which guarantees the unit power factor operation and enhances the grid’s performance. The simulation results for both sides of RES are carried out in MATLAB/Simulink, and these results are verified experimentally through the dSPACE-1103 hardware.

Omni-Directional Ultrasonic Powering via Platonic Solid Receiver for mm-Scale Implantable Devices

Despite the recent advancements in implantable microdevices, providing sufficient electrical power to deeply seated microsystems has remained challenging due to the small dimension of the system, limiting the total storable energy. Ultrasound powering, where a portion of the externally induced ultrasonic wave is converted to electrical power by a small receiver, has been explored as an attractive source of power, especially for deeply seated implantable microdevices. While all other components have been advanced and miniaturized, the ultrasonic receiver is still a slab of bulk piezoelectric materials, e.g., diced PZT (lead zirconate titanate). Such a rectangular or disc shape is not an ideal form factor for wireless ultrasonic power transfer due to many challenges, particularly angular sensitivity with respect to an incoming ultrasonic wave. In this paper, we present the first demonstration of omnidirectional ultrasonic powering enabled by the high geometrical symmetry of three-dimensional polyhedral shapes. Based on our 3D printing technique of lead-free piezoelectric barium titanate ceramic, we designed highly symmetric, miniaturized, regular polyhedra, known as Platonic solids (i.e., cube, octahedron, dodecahedron), as well as a sphere. For each geometry, we investigate the effect of axial and radial piezoelectric poling, output power levels, efficiency, and angular sensitivity while the surface areas are the same. Across all the geometric shapes, radially poled Platonic solid receivers produce at least 1 order of magnitude larger electrical power density compared to diced PZT. Further, we observed that the higher the order of Platonic solid, the more excellent power transfer efficiency and omnidirectionality. The 3D printability of the Platonic solid also allows for customizable packaging, which we implemented as an implantable light source. Overall, the proposed ultrasonic powering scheme warrants a revolutionary solution for implantable biomedical devices.

Implications of spring-like air compressibility effects in floating coaxial-duct OWCs: Experimental and numerical investigation

The paper analyses the spring-like air compressibility effect in coaxial-duct oscillating-water-column (CD-OWC) wave energy converters (WECs). This is accomplished through a novel non-linear time-domain model for OWC WECs implemented in the object-oriented language Modelica. Good agreement was observed between numerical and physical model testing results. The air chamber volume significantly affected the spring-like air compressibility effect and the converter performance. Another significant factor is the damping level of the power take-off system. Both fixed and floating CD-OWC versions were numerically investigated, focusing on the compressibility effect. Differences were found mainly due to the additional degrees of freedom in floating configurations. In general, numerical and experimental results showed that air compressibility might positively or negatively affect device power performance in regular waves, depending on whether the frequency is within or out of an interval defined by critical frequencies. Some particular points were observed and categorised as Equicompressum Nullum and Equicompressum critical points, representing different characteristics. Knowledge of these critical values might be important in OWC control. Finally, some applications of the CD-OWC concept are discussed, including considerations on the power output level provided by biradial and Wells air turbines.

High-harmonic large-orbit terahertz gyrotrons for physical applications

An overview is given of works on two experimental installations that implement large-orbit gyrotrons (LOG) operating in the sub-terahertz frequency range at high harmonics of the electronic cyclotron frequency. At the installation of a pulsed LOG (80–100 keV/0.7–1.0 A), a radiation source with a frequency of 1 THz with a kilowatt output power level is being developed, which is planned to be used in plasma applications. A continuous subterahertz LOG (30 keV/0.7 A) is being created as a prototype of a universal multi-frequency source for spectroscopic applications. Complex electrodynamic systems are also described, designed to increase the selectivity and efficiency of excitation of high cyclotron harmonics in these devices, as well as to ensure the tuning of the generation frequency.

Performance Evaluation and Comparison of Three-Phase and Six-Phase Winding in Ultrahigh-Speed Machine for High-Power Application

This article investigates the influence of multiphase winding topologies in high-power ultra-high-speed machines (HP-UHSM) of 500 kr&#x002F;min. At this speed level, increasing the rotor&#x0027;s magnetic loading excites its critical bending resonances and leads to structural breakdown. On the other hand, increasing the stator&#x0027;s electric loading using the three-phase winding increases unwanted vibrations in a slotted stator and reduces the electromagnetic inter-action of the stator and rotor in a slotless stator. Consequently, the maximum output power level of UHSM (500 kr&#x002F;min or more) is limited to a few hundred watts only in the state-of-the-art. To over-come such a critical limitation, this article proposes a new design methodology for HP-UHSM, where the rotor&#x0027;s bending resonances and centrifugal stresses are restricted by limiting the maximum aspect ratio (<i>L&#x002F;D</i>), and an optimal multiphase winding is adopted in the slotless stator to increase the power level by effective electric loading. Also, a Multiphysics optimization is utilized to obtain the optimum magnetic loading and electric loading, where the bending resonance and other system limits are defined using multi-disciplinary design constraints. It is observed that the multiphase winding provides an added degree of freedom to increase the power level of UHSM without exciting the rotor&#x0027;s bending resonances and structural breakdown. Using the proposed method, a multiphase 2 kW 500 kr&#x002F;min HP-UHSM has been designed for the safety-critical AMEBA system and compared its Multiphysics performance with the three-phase machine having the same volume. Finally, exten-sive experiments are performed on both prototypes to validate the effectiveness of the proposed method. It is shown that the multi-phase HP-UHSM has no critical bending resonance below the 500 kr&#x002F;min, and it has 16.3&#x0025; higher output power with 1.18&#x0025; higher efficiency and 28.6&#x0025; lower back-EMF than the three-phase design.

Enhancing Zinnia (Zinnia elegans Jacq.) Seed Quality through Microwaves Application

In organic farming, microwave irradiation can be used as an alternative to standard chemical seed treatment. The increase in temperature during this treatment may negatively affect the germination of low-quality seeds. The aim of the study was to evaluate the effect of microwaves on germination and the health of zinnia seeds using four seed samples varying in initial seed quality. Seeds were placed in a beaker with distilled water and irradiated at power output levels of 500, 650 and 750 W for 30, 35, 40, 45 and 50 s. Controls were untreated seeds, seeds treated with fungicide and seeds soaked in water for 30, 35, 40, 45 and 50 s. Germination and health tests were performed for controls and microwave-treated seeds. Analyzed samples differed in seed quality and response to microwave irradiation. Improvement in seed germination after microwave treatment was observed in three of the tested samples. The fungi Alternaria alternata, A. zinniae and Fusarium spp. prevailed on the seeds. Microwave treatment, especially at power outputs of 650 and 750 W, usually positively affected seed health, significantly increasing the number of seeds free of fungi, but when water temperature during treatment exceeded 60 °C significant deterioration in germination parameters was observed in all tested samples.

Improvement of AlGaN/GaN HEMTs Linearity Using Etched-Fin Gate Structure for Ka Band Applications.

In this paper, AlGaN/GaN high electron mobility transistors (HEMTs) with etched-fin gate structures fabricated to improve device linearity for Ka-band application are reported. Within the proposed study of planar, one-etched-fin, four-etched-fin, and nine-etched-fin devices, which have 50-μm, 25-μm, 10-μm, and 5-μm partial gate widths, respectively, the four-etched-fin gate AlGaN/GaN HEMT devices have demonstrated optimized device linearity with respect to the extrinsic transconductance (Gm) value, the output third order intercept point (OIP3), and the third-order intermodulation output power (IMD3) level. The IMD3 is improved by 7 dB at 30 GHz for the 4 × 50 μm HEMT device. The OIP3 is found to reach a maximum value of 36.43 dBm with the four-etched-fin device, which exhibits high potential for the advancement of wireless power amplifier components for Ka band applications.

Design and off-design performance analysis of a liquid carbon dioxide energy storage system integrated with low-grade heat source

Nowadays, developing the renewable energy has become the worldwide consensus. Nevertheless, the intermittency and volatility of renewable electricity bring great challenges to the stability of the power grid. Liquid carbon dioxide energy storage is recognized as one of the most promising technologies to overcome these difficulties. In this paper, a liquid carbon dioxide energy storage system integrated with the low-grade heat source is proposed. Based on the preliminary geometric parameters of system components, investigations on the system design and off-design performances are carried out. Results of parametric analysis indicate that the pseudo-critical point corresponding to 8 MPa is recommended as the design point for compressor inlet, and the minimum value of LCOE could reach 9.49 cents/kWh. Under design conditions, the system exergy efficiency reaches 48.42% and the roundtrip efficiency is 63.60%. Moreover, 10.70 cents/kWh of the per unit generation cost is advantageous in the large-scale energy storage systems. With the variations of input power (70%∼120%) and output power level (50%∼100%), the surplus water ratio could reach 23.63% at 50% load level, while the variation range of exergy efficiency is 15.56%∼48.42%. Meanwhile, the roundtrip efficiency varies from 22.16% to 63.60% under off-design conditions, and the maximum value is achieved at the design point. All the results identify the feasibility of the integrated energy storage system.

Lengthy Testing of a K-Band Multifrequency Gyro-TWT With Double-Disk External Reflector

We present the results of experimental investigations of multifrequency oscillations in a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\textit{K}$</tex-math> </inline-formula> -band gyrotron traveling-wave tube (gyro-TWT) with double-disk external reflector. The system operation in multifrequency regime was tested for a prolonged period of time with temperature monitoring by an infrared camera. Based on the measurement results, the possibility of stable generation for a period of several tens of minutes at the output power level of more than 2 kW is demonstrated.

Microwave Frequency Doubler with Improved Stabilization of Output Power

The passive multipliers based on semiconductor diodes, most frequently a Schottky type, should be driven by a certain value of input power, where the conversion losses are optimal. This means that the variation in the input power level causes the change in the output power level. A solution to this issue is the integration of an output power amplifier, which in the state of saturation provides quasi-stabilization of the output power. Practically, this approach gives an unsatisfactory performance: weak stabilization or narrow input power range. This paper comprises a concept of an active frequency multiplier with the use of one FET transistor and a special adaptive bias circuit in order to obtain a very wide input power range when the output power is stable. The principle of the operation, design guidelines, and measurement results have been presented for an example circuit of the frequency doubler. The results show the possibility to obtain up to 10 dB input power range for a 1 dB change in output power level without the use of additional amplifiers.

Current Achievements in Flexible Piezoelectric Nanogenerators Based on Barium Titanate

Harvesting ambient mechanical energy at the nanometric scale holds great promise for powering small electronics and achieving self-powered electronic devices. The current review is focused on kinetic energy harvesters, particularly on flexible piezoelectric nanogenerators (p-NGs) based on barium titanate (BaTiO3) nanomaterials. p-NGs based on nanotubes, nanowires, nanofibres, nanoplatelets, nanocubes or nanoparticles of BaTiO3 fabricated in vertical or lateral orientation, as well as mixed composite structures, are overviewed here. The achievable power output level is shown to depend on the fabrication method, processing parameters and potential application conditions. Therefore, the most widely studied aspects, such as influence of geometry/orientation, BaTiO3 content, poling process and other factors in the output performance of p-NGs, are discussed. The current standing of BaTiO3-based p-NGs as possible candidates for various applications is summarized, and the issues that need to be addressed for realization of practical piezoelectric energy harvesting devices are discussed.

Power-scaled CW Alexandrite lasers

We present several strategies for increasing the output laser power of near-diffraction limited continuous-wave Alexandrite lasers pumped by fibre-coupled red laser diodes. Laser mode size control using a convex mirror with the varying thermal lens is shown to be an efficient method for generating record levels of output power from a diode-pumped Alexandrite laser. 8.6 W is obtained with M^{2}<1.1 and an optical efficiency of 27%. 735–790 nm wavelength tuning is demonstrated with > {2.5},hbox {W} and a record dual-wavelength output power of 4.2 W. In a ring-cavity geometry, 5.1 W is obtained with M^{2}<1.1 showing promising potential for multi-watt single-longitudinal-mode operation. Detailed laser cavity modelling including thermal lens analysis is also provided.

Design of a Dynamic Hybrid Compensator for Current Sharing Control of Parallel Phase-Shifted Full-Bridge Converter

The phase-shifted full-bridge (PSFB) converter has been widely used in power supply modules due to its simple control and high output power. However, with the market’s increasing demand for higher power sources, the PSFB converter needs to face challenges in increasing its output power level. Compared to redesigning a larger power module or a larger single converter, it will be more cost-effective to achieve a higher power output by paralleling the existing converters. However, due to the manufacturing differences in circuit components, the output imbalance in parallel PSFB converter systems may damage the power modules. Thus, the influence of differences in circuit components is analyzed in this paper, and it is found that the leakage inductance and transformer ratio are the main factors resulting in errors in current sharing control. Consequently, a dynamic hybrid compensator (DHC) is proposed in this paper, that can significantly reduce the error in current sharing control via the compensation of the duty cycle of a slave module. Furthermore, the DHC is verified on an 800 W two-phase PSFB converter, which shows that even when the difference in components is as large as 20%, the proposed method can still reduce the error in current sharing control to less than 2% under both half and full load conditions.

High saturation photocurrent THz waveguide-type MUTC-photodiodes reaching mW output power within the WR3.4 band.

In this paper, we report on waveguide-type modified uni-traveling-carrier photodiodes (MUTC-PDs) providing a record high output power level for non-resonant photodiodes in the WR3.4 band. Indium phosphide (InP) based waveguide-type 1.55 µm MUTC-PDs have been fabricated and characterized thoroughly. Maximum output powers of -0.6 dBm and -2.7 dBm were achieved at 240 GHz and 280 GHz, respectively. This has been accomplished by an optimized layer structure and doping profile design that takes transient carrier dynamics into account. An energy-balance model has been developed to study and optimize carrier transport at high optical input intensities. The advantageous THz capabilities of the optimized MUTC layer structure are confirmed by experiments revealing a transit time limited cutoff frequency of 249 GHz and a saturation photocurrent beyond 20 mA in the WR3.4 band. The responsivity for a 16 µm long waveguide-type THz MUTC-PD is found to be 0.25 A/W. In addition, bow-tie antenna integrated waveguide-type MUTC-PDs are fabricated and reported to operate up to 0.7 THz above a received power of -40 dBm.

A wideband hybrid combiner design for ITER ion cyclotron radio frequency source.

The high-power radio frequency source for ion cyclotron heating and current drive of ITER tokamak consists of two identical 1.5MW amplifier chains. These two chains will be combined using a wideband hybrid combiner with adequate coupling flatness, phase balance, return loss, and isolation response to generate 2.5MW radio frequency (RF) power in the frequency range of 36 to 60MHz. As part of the in-house development program at ITER-India, a wideband hybrid combiner with coupling flatness and return loss/isolation better than 0.4 and -25 dB, respectively, has been simulated. A detailed analysis for matched load performance of the hybrid combiner for the output power level of 3MW as well as mismatched load performance for load power of 2.5MW with voltage standing wave ratio 2.0 and 3.0MW with voltage standing wave ratio 1.5 has been performed. Based on the simulation, a prototype model was in-house fabricated, and the simulated results have been validated experimentally in splitter and combiner mode. To evaluate performance as a combiner, two solid-state power amplifiers were combined through the prototype combiner for input power levels up to 2.5 kW on matched and mismatched load conditions. In the power splitter experiment, the RF power level up to 1.5MW from a single amplifier chain was split through the prototype combiner to be dumped in the high power loads in the frequency range of 36 to 60MHz.

Effect of Cadence on Physiological and Perceptual Responses during Eccentric Cycling at Different Power Outputs.

The effect of cadence in eccentric (ECC) cycling on physiological and perceptual responses is, to date, poorly understood. This study aimed to evaluate the effect of cadence during ECC cycling on muscular activation (EMG), oxygen consumption (V̇O 2 ), and perceived effort (PE) for two different levels of power output. Seventeen participants completed four sessions 1 wk apart: 1) determination of the maximal concentric peak power output (PPO) and familiarization with ECC cycling at five cadences (30, 45, 60, 75, and 90 rpm); 2) second familiarization with ECC cycling; 3) and 4) ECC cycling exercise consisting of 5 min at the five different cadences at either 40% or 60% PPO. PE was reported, and V̇O 2 and EMG of seven muscles were calculated over the exercise's last minute. PE, V̇O 2 , and global lower limb muscles activation (EMG ALL ) showed an effect of cadence ( P < 0.001) and followed a curvilinear function. Both low and high cadences increased PE and V̇O 2 responses compared with intermediate cadences. Although muscle activation of vastus lateralis follows a U-shaped curve with cadence, it was greater at low cadence for rectus femoris and biceps femoris, greater at high cadence for tibialis anterior and gastrocnemius medialis, and was not altered for soleus. The estimated optimal cadence was greater (all P < 0.01) for V̇O 2 (64.5 ± 7.9 rpm) than PE (61.7 ± 9.4 rpm) and EMG ALL (55.9 ± 9.3 rpm), but power output had no effect on the optimal cadences. The physiological and perceptual responses to changes in cadence during ECC cycling followed a U-shaped curve with an optimal cadence depending on the parameter considered.

Hybrid Propulsion Efficiency Increment through Exhaust Energy Recovery—Part 1: Radial Turbine Modelling and Design

The efficiency of Hybrid Electric Vehicles (HEVs) may be substantially increased if the energy of the exhaust gases, which do not complete the expansion inside the cylinder of the internal combustion engine, is efficiently recovered by means of a properly designed turbogenerator and employed for vehicle propulsion; previous studies, carried out by the same authors of this work, showed a potential hybrid vehicle fuel efficiency increment up to 15% by employing a 20 kW turbine on a 100 HP rated power thermal unit. The innovative thermal unit here proposed is composed of a supercharged engine endowed with a properly designed turbogenerator, which comprises two fundamental elements: an exhaust gas turbine expressly designed and optimized for the application, and a suitable electric generator necessary to convert the recovered energy into electric energy, which can be stored in the on-board energy storage system of the vehicle. In these two parts, the realistic efficiency of the innovative thermal unit for hybrid vehicle is evaluated and compared to a traditional turbocharged engine. In Part 1, the authors present a model for the prediction of the efficiency of a dedicated radial turbine, based on a simple but effective mean-line approach; the same paper also reports a design algorithm, which, owing to some assumptions and approximations, allows a fast determination of the proper turbine geometry for a given design operating condition. It is worth pointing out that, being optimized for quasi-steady power production, the exhaust gas turbine considered is quite different from the ones commonly employed for turbocharging application; for this reason, and in consideration of the required power size, such a turbine is not available on the market, nor has its development been previously carried out in the scientific literature. In the Part 2 paper, a radial turbine geometry is defined for the thermal unit previously calculated, employing the design algorithm described in Part 1; the realistic energetic advantage that could be achieved by the implementation of the turbogenerator on a hybrid propulsion system is evaluated through the performance prediction model under the different operating conditions of the thermal unit. As an overall result, it was estimated that, compared to a reference traditional turbocharged engine, the turbocompound system could gain vehicle efficiency improvement between 3.1% and 17.9%, depending on the output power level, while an average efficiency increment of 10.9% was determined for the whole operating range.

Optimal Allocation of Curtailment Levels of PV Power Output in Different Regions in Consideration of Reduction of Aggregated Fluctuations

Optimal Allocation of Curtailment Levels of PV Power Output in Different Regions in Consideration of Reduction of Aggregated Fluctuations

Analysis, Design, and Validation of a Decoupled Double-Receiver Wireless Power Transfer System With Constant Voltage Outputs for Industrial Power Supplies

Unwanted cross-couplings greatly hinder the development of double-receiver wireless power transfer (WPT) systems. Whenever the air gap changes or misalignment occurs, cross couplings disrupt the system stability. This article investigates a magnetic coupler for a double-receiver WPT system, which dramatically suppresses the unwanted cross-couplings. Two types of undesirable couplings are significantly reduced by using orthometric DD coils and Q-shaped coils. First, the unwanted couplings between receivers can be eliminated, validated by the measured coupling coefficient <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">k</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">AB</sub> = 0.003. Therefore, two receivers can work independently. Second, the unwanted couplings among the source coil and receivers can be eliminated ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">k</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1A</sub> = 0.003 and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">k</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1B</sub> = 0.003), resulting in load-independent constant voltage output. Compensation networks can also be designed straightforwardly. In addition, the inverter can achieve zero phase angle, alleviating volt-ampere rating and increasing efficiency. Thanks to the presented structure, this coupler design process is efficient because the decoupling is from the shape rather than turns. Also, it can be easily generalizable to other output voltage or power levels since turns can be changed to meet different charging demands. Validated by a laboratory prototype, experimental results successfully show remarkable agreement with the theoretical analysis, ensuring 72 V load-independent constant output voltages. It also realizes a 90.16% maximum measured overall dc–dc power transfer efficiency with 12 cm air gaps when delivering 518.4 W to two 20 Ω loads.