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Given that low-carbon development has become an important goal for the sustainable development of the industrial sector, the development of low-carbon industrial parks is conducive to advancing the low-carbon development of China's industry. Based on the development status quo of industrial parks in China's textile industry, this article adopted literature research, qualitative and quantitative analysis, and expert consultation to establish an evaluation indicator system for low-carbon industrial parks characterized by a scoring mechanism comprising three levels with thirty indicators. Meanwhile, considering the requirements of policies, documents, regulations, and standards related to energy consumption and low-carbon development in the textile industry, these indicators' benchmark values and evaluation criteria were calculated and determined. Then, this article selected the parks dominated by garment, chemical fiber manufacturing, and textile industries for low-carbon evaluation demonstrations. The low-carbon zone evaluation index system developed in this article could realize the monitoring, assessment, and comparison of the low-carbon levels of industrial parks, thereby facilitating the planning, construction, and management of low-carbon parks in the textile industry. [ABSTRACT FROM AUTHOR]

Copyright of Industria Textila is the property of Institutul National de Cercetare-Dezvoltare pentru Textile si Pielarie and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The release of microplastic fibers (MPFs) during washing is the main source of microplastic pollution in water environment. Mechanical action is the principle factor affecting the release of MPFs during washing. In order to better understand the effect of washing mechanical action on the release of MPFs, a washing simulation device was designed to study the effects of abrasion action, hydrodynamic flow action and beating action on the release of MPFs. The results show that there is a certain amount of floating MPF in the fabric due to the production process. The floating MPFs can be released in large quantities even though the mechanical action is weak, accounting for about 28% of the total MPF release. In addition, the release of secondary MPFs increases with the mechanical action. The increase of the abrasion times between fabric and fabric has the most significant effect on the release of MPFs. Compared with 60 abrasion times, the number of MPFs increased by about 16% and the average length decreased by 40% when abrasion was 5000 times. This study enhances the understanding of how mechanical action during washing affects the release of MPFs. This emphasizes the impact of floating MPFs, as well as the need to optimize the washing process to reduce the emission of MPFs. [ABSTRACT FROM AUTHOR]

Copyright of Industria Textila is the property of Institutul National de Cercetare-Dezvoltare pentru Textile si Pielarie and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Maintaining human thermal comfort in cold indoor environments is crucial but usually involves excessive energy consumption and massive greenhouse gas emissions. Thermoregulating the human body by using advanced clothing is emerging as a promising solution to effectively and energy-efficiently achieve personal thermal management. An air inflatable suit (AirST) using a series of air chambers as the thermal insert was developed for the purpose of adjusting clothing thermal insulation and hence improving personal thermal comfort. The thermal insulation regulating performance of AirST was investigated through thermal manikin tests and wear trials. Compared with the AirST without air inflation, AirST after inflation with air had a desired effect, which could not only increase local clothing thermal insulation by a range from 4.5% to 24.8% but also alleviate cold strain and provide significantly higher local skin temperatures, mean skin temperature and mean body temperature. After inflation, AirST successfully improved the whole-, upper- and lower-body thermal sensations in a cool environment. The acceptable heating setpoint temperature by the air conditioner could be decreased while using AirST with inflation, which saved approximately 30% of building energy consumption. As the AirST without air inflation can also be worn as regular windproof clothing, this versatility saved approximately 12 kg CO2e emissions in the production process. [ABSTRACT FROM AUTHOR]

During the growth of biomass, there are two carbon storage paths for plant-derived fibers. One path is to assimilate carbon dioxide (CO2) from the atmosphere through photosynthesis and temporarily store it in textile plants. Besides, the carbon can be captured and stored in soil. The carbon storage capacity of textile products made from plant-derived fibers such as cotton, flax, hemp, kenaf and bamboo fiber, etc., is a non-negligible part of greenhouse gas (GHG) accounting and reporting. However, there is a lack of systematic methods to evaluate carbon storage and the delayed emission effect of plant-derived fibers. In this study, the carbon storage and emission times of 100% hemp T-shirt, 100% hemp slipcover, and 100% hemp fiber handicraft were evaluated by using the soil organic carbon method, dry weight biomass method, and modeling method. The results revealed that the CO2 storage of 1 kg hemp fiber is 1.833 kg. Meanwhile, the delayed emission effects of carbon temporarily stored in the 3 kinds of hemp fiber products are 3.83%, 19.68%, and 41.12% at different lifespans (i.e., 5, 25, or 50 years), in which case the landfill option for hemp fiber products may be preferable from carbon storage effect perspective. The results suggest that plant-derived fibers have a positive impact on climate change due to CO2 storage, and that the carbon storage effect improves with the continued lifespan of the product. By quantifying carbon storage and the delayed emission effect of plant-derived fibers, it is beneficial to understand the potential for reducing carbon emissions, which in turn helps to promote and develop more environmentally friendly and low-carbon production processes and products. [ABSTRACT FROM AUTHOR]

Copyright of Industria Textila is the property of Institutul National de Cercetare-Dezvoltare pentru Textile si Pielarie and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

While the very high switching speed of the gallium nitride devices can easily enable power electronics converters to operate at multi megahertz, it also brings huge challenges to switching current measurement, which is very important for the evaluation of switching performance. The conventional switching current measurement methods either have low bandwidth or have influence on layout inductance. To address these issues, this article proposes a high-bandwidth and easy-to-integrate switching current measurement method, with almost no influence on power loop layout. The proposed method utilizes the power loop trace from the source terminal of bottom switch to circuit ground as the sensing trace. By measuring the sensing voltage and considering the frequency-dependent parasitic inductance and resistance of the sensing trace, the switching current is derived based on the Fourier series theory. The simulation verification is firstly performed by using LTspice, and shows consistent results. Then, to accurately measure the sensing voltage, the used voltage probe TPP1000 is carefully modeled for measurement compensation and correction. Finally, two double pulse test (DPT) boards are designed, one with coaxial current shunt and the other without coaxial current shunt. Through DPT experiment, the accuracy of the proposed method with almost no insertion inductance is verified. [ABSTRACT FROM AUTHOR]

Due to the outstanding material properties, silicon carbide (SiC) power device is the most promising alternative to silicon devices and can work at higher junction temperature. However, existing packaging technologies obstruct the use of SiC devices at high temperature and impede the continued exploration of SiC devices in high-temperature applications. This article proposes a novel hermetic metal packaging method called compact-interleaved package. The compact-interleaved power module handles the mentioned problems from three key considerations: packaging parasitic parameters, direct electrode measurement structure, and packaging materials. Based on the elaborate high-temperature double pulse test platform, dynamic characteristics of 1.2-kV/13-mΩ 4H-SiC power mosfet are studied under the condition of extremely high junction temperature (up to 550 °C) and extremely high switching speed (about 3 kA/μs). The dynamic characteristics of SiC mosfet are theoretically analyzed and verified by experimental measurements. Compared with other SiC bipolar devices, SiC mosfet maintains outstanding dynamic characteristics at extremely high temperatures and has an optimal operating high-temperature range. Finally, this article demonstrates an extreme-high-temperature power electronic converter to verify the superiority of the packaging method, and also proves the extreme-high-temperature power converting capability of SiC mosfet. [ABSTRACT FROM AUTHOR]

In global trade, the manufacture and consumption of cotton textile products are intervening in the hydrological cycle. To address the relationship between the product system and the unsustainable use of local water resources, a spatial water footprint assessment is needed. This study presents a spatial water footprint method that was demonstrated in the case of domestically produced cotton T-shirts in three recycle scenarios. The results showed that the water scarcity footprint of conventional T-shirt, eco T-shirt, recycled T-shirt is 2.45 H2O eq, 1.74 H2O eq, 8 × 10−2 H2O eq, respectively, and the water-eutrophication footprint of conventional T-shirt, eco T-shirt, recycled T-shirt is 1.18 × 10−2 PDF·m2·yr−1, 9.47 × 10−3 PDF·m2·yr−1, 4.04 × 10−3 PDF·m2·yr−1, respectively. Two interesting results have been found. Firstly, the hydrosphere has been affected by manufacture and consumption; thus any choice made by manufacturers and consumers may lead to an impact on the water resource in a region that is far from the location. Secondly, the effect of water footprint reduction will be more apparent in places with severe water stress. The spatial water footprint offers a transparent result of each phase's potential contribution to the local environment and could make a quantitative comparison between product stages, products, and local impacts. Thus, spatial water footprint will be a critical component in the sustainability management improvement of the supply chain. [ABSTRACT FROM AUTHOR]

In high-load-current LLC dc–dc converter, synchronous rectification (SR) is usually used to reduce the secondary loss. As a lossless, low-cost, and small-volume SR control strategy, the drain–source voltage of SR switches sensing method is used widely in industrial applications. However, when the load current increases, the voltage ringing across SR switches during O stage is more and more severe and reaches zero eventually. When the voltage ringing reaches around zero in LLC converter, the voltage-sensing-method SR controller will generate the false driving signal, which makes SR switches turn on early and causes the converter works abnormally. This article presents the accurate analysis and design of the circuit parameters of LLC dc–dc converter to prevent the voltage ringing across the SR switches reaches around zero. The voltage ringing model is established, and the parameters design principle is given. By using the proposed design guideline, the voltage ringing across SR switches will always be higher than zero over the full load range, which eliminates the turn-on early issue or turn-on several times in one cycle issue. Therefore, this article can provide a design reference and guideline for the high-load-current and high-output-power LLC converter with voltage sensing SR control strategy. A 2.16 kW SR LLC dc–dc converter prototype is built according to the proposed design guideline, and the experimental results verify the correctness and effectiveness of the analysis. [ABSTRACT FROM AUTHOR]

Extracting gate-drain overlap oxide capacitance (Coxd) is a necessary step for almost all kinds of insulated-gate bipolar transistor (IGBT) compact models. There are two datasheet-driven methods that are universally accepted, one is based on reverse capacitance voltage characteristics (C–V method), and the other uses gate charge characteristics (Q–V method). This letter is to reveal the underlying mechanism of these two methods. It is found that the C–V method has an inescapable shortcoming which will mistake the turn-off delay time forecasted by IGBT models. In this letter, the internal capacitance system of IGBT is modeled and demonstrated completely. Based on this model, the accuracy and feasibility of the C–V and Q–V methods are analyzed. Moreover, the effect of Coxd on IGBT compact models is studied and further verified by experiments and circuit simulations. [ABSTRACT FROM AUTHOR]

SiC JFET/Si mosfet Cascodes (SSCs) are promising because of their small on-resistance and fast switching speed. Parallel operation of multiple SSCs is popular for high-current applications. However, the practical layout can hardly be absolutely symmetric. The mismatches from layout will cause turn-on current imbalance among paralleled SSCs. The maximum current stress will be aggravated for some SSCs. Besides, unbalanced current can lead to uneven losses. Then, the junction temperature difference (ΔTj) between paralleled SSCs occurs. The maximum junction temperature (Tjmax) among paralleled SSCs increases accordingly. To address the issue, a low-cost and novel structure is proposed to promote turn-on current sharing for paralleled SSCs. With aid of the structure, the immunity of turn-on current sharing performance to an asymmetric layout can be greatly improved. The mismatched turn-on current and losses can be well mitigated. ΔTj and Tjmax are suppressed at the same time. The proposed structure is suitable for both the discrete SSCs and bare-die SSCs. In this structure, only some bridging branches are introduced so it takes almost no extra cost. Two prototypes are fabricated with the discrete SSCs and bare-die SSCs, respectively. Double-pulse test and continuous operation are conducted to validate the advantages of the proposed structure. [ABSTRACT FROM AUTHOR]

In this article, high step-down dc–dc converters are widely employed in data center applications. Due to the higher step-down conversion ratio in the new generation 48 V voltage regulator module, a conventional buck converter is not suitable for such applications. To conquer this problem, a novel dc–dc converter is proposed in this article to achieve an ultrahigh step-down voltage conversion ratio for data centers. The nonisolated topology can be optimally designed to integrate both the switched-capacitor and coupled inductor techniques, which allows zero-voltage-switching (ZVS) of all active switches to be achieved and improves high efficiency. In addition, the converter presents the advantages of lower voltage stress, ultrahigh voltage gain, common ground, and simple control strategy. A comprehensive analysis of the steady-state analysis, derivation of voltage gain, voltage stress, and ZVS condition is presented in detail. Finally, a 30 W, 48-to-1 V experimental prototype is built and tested, which validates the ultrahigh step-down voltage gain and soft-switching characteristic of the proposed converter. The maximum efficiency of the prototype is 89.1% and the efficiency is 81.4% in full-load condition. [ABSTRACT FROM AUTHOR]

Practices in the textile and apparel industry (TAI) have led to numerous environmental and social problems, which have prompted extensive research on the sustainable development of the textile and apparel industry (SDTAI). This paper presents a comprehensive and quantitative analysis of the status quo in the SDTAI domain using scientometrics. From 1987 to 2019, the Web of Science core collection databases (SCI and SSCI) included 863 journal articles related to SDTAI, and our analysis results were as follows: (1) 60 critical research keywords occur in the knowledge base; (2) four research hotspots were identified; (3) five themes constituted the main knowledge area; and (4) based on the knowledge base, research hotspot, and knowledge domain, the knowledge structure consisted of nine subjects and five systems. This paper proposes a knowledge roadmap that can be helpful for practitioners and academicians to better understand the current sustainable development status and trends in the TAI. [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]

The bidirectional CLLC resonant converter has distinguished potential in battery chargers and energy storage systems for its advantages in soft switching and bidirectional power flow capability. However, traditional CLLC converters generally adopt symmetrical design to maintain bidirectional symmetrical characteristics, which means the secondary LC network is designed to be equal to the primary LC network after reflection. The symmetrical design is only suitable for voltage grade matching scenarios where a wide voltage range is not required, such as CLLC-type dc transformers. Whereas in the field of bidirectional chargers, due to the wide voltage range of battery, there are significant differences in the characteristics required between charging and discharging mode, which makes symmetrical design no longer applicable. To cope with this issue, this paper proposes a novel design methodology of CLLC based on parameter equivalent and time domain model. With the parameter equivalent principle, the CLLC resonant tank with arbitrary parameters is investigated to satisfy the requirements of wide voltage range for bidirectional charger application. Compared with the symmetrical design, the proposed method can meet the requirements of bidirectional gain within preset frequency range and guarantee the achievement of zero-voltage switching under required load conditions with the minimum reactive power. In addition, the area product capacity of the magnetic part of the CLLC resonant tank is minimized based on the parameter equivalent principle. Finally, experiments have been performed on a 1 kW prototype to confirm the validity and feasibility of the proposed design methodology. [ABSTRACT FROM AUTHOR]

Wireless power transfer (WPT) is a promising way of charging electric vehicles (EVs) for its convenience, safety, physical and electric isolation. For satisfying the high-power application or rapid charging, WPT systems based on multiple coils are usually used. Nowadays, LCC compensation is a commonly used topology. However, the conflict between the installation space limitation and the large volume induced by compensated inductors and multiple coils brings the critical challenge for EVs charging electric vehicles' charging. In this article, a method of integrating multiple decoupled coils is put forward. All the main coils and compensated inductors are integrated together for compacting the WPT system. Characteristics of the coupler are analyzed when it exists a misalignment both in x- direction and y-direction. Besides, an antimisalignment strategy based on optimizing the phase difference of current in main coils is proposed. Finally, a 3kW laboratory prototype is built to verify the proposed compact coupler and antimisalignment control strategy. The system output power only drops 3.2% and 9.2% respectively with a −200 mm and +200 mm misalignment in the x-direction compared with full alignment by adopting the proposed antimisalignment method. When it is fully aligned, the system can achieve 94%peak efficiency. [ABSTRACT FROM AUTHOR]

Relying on the advantages of small size, good controllability, and consistency, printed circuit board (PCB) inductors are being widely used. For PCB inductors, reducing copper loss is one of the key issues. Although some research works focus on fringing effect in PCB planar winding, there are few methods to reduce proximity loss for PCB inductor. Regarding the abovementioned issues, this letter first improves the Ferreira’s 1-D copper loss model to accommodate the core feature of PCB winding: variable number of turns per layer. With this model, pyramid theorem is proposed that putting the layer with fewer turns into positions farther away from the air gaps can lower the total winding loss. Based on the theorem, this letter proposes a novel PCB inductor-winding structure named pyramid winding, which has fewer (or equal) turns on layers farther from air gaps. Pyramid winding has less copper loss, fewer copper layers, smaller size, and lower cost. In the experiment, inductor prototypes with the same six turns and ferrite pot cores but different PCB winding arrangements are built for a 300-kHz 2700-W LLC converter. Tests on inductor resistance and converter efficiency are done, and the pyramid theorem and the effectiveness of pyramid winding are verified. [ABSTRACT FROM AUTHOR]

A nonisolated bidirectional dc–dc converter is proposed for energy storage systems in this article. The proposed converter is composed of three active switches, two synchronous rectifiers, two clamping capacitors, and two inductors. The proposed converter has advantages of being a simple structure, a fewer number of components, a common ground, lower voltage stress, and wide voltage gain range. Compared with the conventional buck converters, the novel converter triples the effective duty cycle and lowers voltage stresses across the active switches. A 300-W/500-kHz GaN-based experimental prototype is built and tested to verify the correctness and validity, demonstrating a peak efficiency of 94.54% in step-down mode and a peak efficiency of 94.88% in step-up mode. [ABSTRACT FROM AUTHOR]

Although with good robustness, insulated gate bipolar transistor (IGBT) modules suffer from catastrophic failures due to excessive electrothermal stress in field use. In view of the coupled and multitimescale electrothermal dynamics of IGBT modules, the conventional simulation methods are difficult to calculate the stresses accurately and efficiently. Therefore, this article proposes an artificial neural network (ANN) based method to calculate the chip-level stress of IGBT modules in system-level circuit simulation. The first contribution in this article is that the research focus goes from the entire device to chips within the device. Correspondingly, the uneven dynamic current and thermal coupling effects among chips are fully considered based on the established uneven power loss and three-dimensional (3-D) thermal models. The second one is to solve the contradiction between simulation efficiency and accuracy in multitimescale operation analysis through the joint application of IGBT physical model and ANN. The third one is to propose the complete chip-level stresses calculation and automated modeling processes, based on multisoftware cosimulation. An inverter experimental prototype was established to verify the accuracy of the proposed calculation method. The comparison results show that the method can accurately describe the transient junction temperature, overcurrent and overvoltage stresses, thus providing an effective support for the safety design of converters. [ABSTRACT FROM AUTHOR]

Smart contact lens has drawn extensive research interests due to the noninvasive real-time detection of the human body to provide biomedical information for health management. However, it has been difficult to accurately measure the physiological signals in tears, and the use of external power source has also hindered the future applications. Here, we demonstrated an organic electrochemical transistor based multiplexed sensors self-powered by the organic solar cells (OSCs). The integrated device was fabricated via simple process including solution blade-coating and thermal evaporation. OSCs were optimized to provide optimal operation voltage for the sensors that exhibit semilog-linear response to the glucose and calcium ions in tear fluids without any peripheral circuits. The sensing signals can be transmitted to the laptop wirelessly through a near filed communication unit. This integrated self-powered multiplexed sensing device will provide real-time monitoring of the biomarkers in tears, prospected to be installed on the smart contact lens for the early detection and diagnosis of diabetes. [ABSTRACT FROM AUTHOR]

Silicon carbide (SiC) power modules are attractive in many applications due to the superiority of their semiconductor characteristics. However, power modules are subjected to repetitive thermo-mechanical stress caused by the mismatch of the coefficient of thermal expansion between different layers of materials. Moreover, the relatively smaller die size of SiC chips makes the heat flux increase significantly, which brings new challenges to the thermal management and reliability of SiC power modules. To tackle these challenges, this article proposes a new thermal enhanced packaging method based on vapor chamber (VC) phase change heat spreader (PCHS) for SiC power modules, achieving the advantages of high thermal conductivity, low weight, low cost, and low thermal stress. In this new design, SiC mosfet bare dies are directly soldered on the top of VC-PCHS, which not only act as heat spreaders but also conduct the drain current of mosfets. The integrated VC-PCHS is optimized based on thermal and thermomechanical performance. An SiC power module prototype directly integrated with VC-PCHS is built using a new fabrication process. Both the simulations and experiments demonstrate significant improvements in thermal and thermomechanical performance. The modules integrated with VC-PCHS can operate under 200 W of power dissipation per die (632 W/cm2) without exceeding the maximum rated junction temperature. This article reveals the potential of directly integrating phase change cooling components inside power modules, providing a new solution to improve the thermal performance and reliability of SiC power modules without adding complexity and energy consumptions to external cooling systems. [ABSTRACT FROM AUTHOR]

Silicon carbon (SiC) metal-oxide semiconductor field-effect transistors (MOSFETs) and SiC/Si cascode devices are two popular normally-off SiC power devices. In terms of the rated voltage and current of a single chip, there are always some SiC/Si cascode counterparts for the SiC MOSFETs. Thus, the two devices can substitute for each other in many fields. However, it is not clear which of the two SiC power devices is more suitable for parallel operation to deal with high current. This article comparatively investigates the paralleling suitability of SiC MOSFETs and SiC/Si cascode devices by theoretical analysis and experimental verifications for the first time. The paralleling suitability of the two devices is quantitatively evaluated by the unbalanced current among paralleled chips under the conditions with asymmetric layout and uneven junction temperature. Both static and dynamic imbalanced current are taken into consideration. Based on the theoretical and experimental results, some design guidelines are proposed to promote current sharing. [ABSTRACT FROM AUTHOR]

For bidirectional CLLC resonant converters, synchronous rectification (SR) is a key technique that can reduce the conduction losses in rectifying side by replacing the diodes with the switches’ channel. However, existing methods suffer from either complex hardware, or incomplete and imprecise control effect. Aiming at solving these problems, this article proposes a digital sensorless SR algorithm based on the time-domain model under a hybrid modulation for CLLC converters. The proposed approach can precisely enable the SR drive action within almost the whole load range and without any additional hardware, e.g., antiparallel diode, SR IC, and high bandwidth sensor. Its implementation only needs to measure dc signals (e.g., the output current), rather than any high-frequency resonant signals. Additionally, the presented algorithm can be easily implemented on a digital controller. Finally, experiments have been performed on a prototype to verify the validity and applicability of the presented SR algorithm. [ABSTRACT FROM AUTHOR]

Double-sided cooling based on planar packaging method features better thermal performance than traditional single-sided cooling based on wire bonds. However, this method still faces thermal and electrical challenges in multichip SiC power modules. Specifically, one is severe thermal coupling among parallel bare dies, and the other is unbalanced current sharing due to unreasonable layout design. This article aims to explore the potentials of SiC power devices in power module, which are higher current capability and reliability. The proposed packaging method is called interleaved planar packaging and can get rid of the optimizing contradiction between thermal and electrical performance. In this packaging method, there are two functional units: interleaved switch unit and current commutator structure. Benefited from the two units’ electromagnetic and thermal decoupling effects, the interleaved power module features low loop inductance, balanced current, low coupling thermal resistance, and even thermal distributions. A 1200 V 3.25 mΩ half-bridge SiC power module based on interleaved planar packaging is fabricated and tested to verify this method's superiority. [ABSTRACT FROM AUTHOR]

Compared with silicon and silicon carbide devices, the unique electrical and structural characteristics of gallium nitride high electron mobility transistors (GaN HEMTs) make them have different requirements for power module integration. This article proposes a novel integration scheme for the high-voltage lateral GaN HEMT dies without bonding wires. Based on the proposed integration scheme, a compact 650 V/30 A GaN power module with low parasitic parameters and high thermal performance is designed. The GaN dies are sandwiched between two ceramic substrates to improve thermal performance and ensure consistent thermal expansion coefficients. The multiple copper layer structure is used to increase wiring flexibility to reduce parasitic parameters. The design of gate and power loop layouts is discussed, and the common-mode (CM) capacitance is optimized. A comprehensive reliability evaluation is also carried out for this integration scheme. Finally, a double-sided cooling 650 V/30 A full-bridge GaN power module with 2.4 cm×1.3 cm×0.17 cm is fabricated. The thermal resistance is reduced by 30%–48% compared with the conventional single-sided cooling module. The power loop and gate loop inductances are reduced to 0.94 nH and 2 nH, respectively, and the CM capacitance is limited to 2.5 pF. The maximum dv/dt of the drain–source voltage is high as 150 V/ns with only 10% overshoot. Based on the power module, a 3.3-kW two-phase interleaved buck converter is developed. It has 820 W/in3 power density and 98.85% peak efficiency. [ABSTRACT FROM AUTHOR]

Polymer-based composites are in great demand in thermal management with better thermal conductivity performance because of the rapid a evolutionary performance of their application systems. Pursuing new filler materials with higher thermal conductivity is an important way to improve the performance of polymer composites. Boron phosphide (BP) has been confirmed to possess the superior characteristic of high thermal conductivity, yet it is difficult to be synthesized on a large scale and thus is rarely used as a filler in composites. In this work, BP powders were synthesized by a facile molten salt method. Afterwards, milled BP (MBP) particles containing abundant surface functional groups were first explored as a filler for nanofibrillated cellulose (NFC) to fabricate NFC/MBP composite films by the vacuum filtration technology. The high thermal conductivity of MBP and the in-plane oriented arrangement, in conjunction with its strong interface bonding with NFC, led to the high in-plane thermal conductivity (17.6 W m−1 K−1) of the composite with 15 wt% MBP. The better heat dissipation capacity than that of the NFC composite with BN nanosheets as the filler makes the NFC/BP film suitable for application in the field of thermal management. [ABSTRACT FROM AUTHOR]

A novel transformer-less topology with high step-down voltage gain is proposed for low-voltage high-current point-of-load voltage regulator modules (VRMs). The proposed topology consists of three capacitors, two inductors, three active switches, and two synchronous rectifiers. It triples the effective duty-ratio and lowers the voltage stresses across active switches compared with conventional buck topologies. Converters based on the topology have a potential benefit of achieving high power density and can be capable of delivering high current to the output by two interleaving phases. Small inductance and capacitance are only needed by using interleaving technology, which results in very fast dynamic response to large load changes. A 60 W, 48–1.8 V prototype is built to verify the performance of the proposed topology. [ABSTRACT FROM AUTHOR]

The parasitic inductor can be used as resonant component to increase the power density in resonant converters. However, the parasitic inductance value of PCB copper traces is not large enough to achieve zero current switching in low and medium switching frequency conditions. To tackle this problem, a novel integration method to increase parasitic inductance value is proposed in this letter. The proposed method is based on direct coupling, which utilizes lateral structure and vertical structure to increase equivalent inductance between two parasitic inductors. The proposed method not only can achieve high efficiency, high power density, and very low profile design, but also can save the cost and space of discrete inductors for the designed prototype in low and medium frequency range. The comparison and design procedure of both lateral and vertical structures of the parasitic inductor are presented in details. Two 100-W prototypes employing gallium nitride devices are built to compare the discrete inductor solution with the proposed parasitic inductor integration method. The power density of the prototype using parasitic inductor is 62.5% higher than discrete inductance and has achieved a peak efficiency of 93.4%. [ABSTRACT FROM AUTHOR]

The snubber circuit is a cost-effective solution to reduce the severe turn-off overvoltage and oscillation caused by the fast switching characteristics of SiC MOSFET. However, the turn-on switching losses will significantly increase as the snubber decouples the power loop parasitic inductance during the switching process. In this article, the effect of the power loop parasitic inductance on the switch performance of SiC MOSFETs and the quasi-zero voltage switching (QZVS) turn-on condition are studied. On this basis, an SiC MOSFET overvoltage and oscillation suppression circuit (OVSC) with not only the switching losses optimization feature but also the clamping energy feedback characteristic is proposed. The overvoltage and oscillation can be effectively suppressed by clamping capacitors, and those capacitors do not participate in the switching process until the overvoltage occurs, which is of benefit to the switching losses reduction compared with the other normal snubber circuits. Besides, the turn-off overvoltage and oscillation energy stored in the clamping capacitors can be feedback to dc and load side through a passive branch composed of an energy feedback inductor and a diode. The experimental studies and comprehensive comparison studies are carried out to verify the validity of the proposed OVSC. The experimental results show that OVSC has excellent overvoltage and oscillation suppression performance and can significantly reduce the switching losses. [ABSTRACT FROM AUTHOR]

To achieve superior thermal and mechanical properties of copper-bonded (Cu-bonded) Si3N4 substrate, a pressure-assisted direct bonded Cu (DBC) technique was applied to bond Cu foil with Si3N4 plate. The effects of oxide layer (SiO2) thickness of Si3N4 plate on the microstructure, thermal and mechanical properties of the Si3N4-DBC samples were investigated. The successful bonding of Cu foil to Si3N4 plate was confirmed by the presence of the interfacial products of Cu2MgSiO4 and CuYO2. Additionally, it was demonstrated that a thin SiO2 layer can result in a discontinuous distribution of interfacial products while a thick one can lead to the formation of pores in SiO2 layer. Notably, the sample prepared by Si3N4 plate with 5-μm-thickness SiO2 layer and Cu foil with 5.9-μm-thickness oxide layer (Cu2O) exhibited the optimally comprehensive properties with thermal conductivity of 92 W·m−1·K−1 and shearing strength of 102 MPa, which demonstrates significant promise for application in power electronic modules. [ABSTRACT FROM AUTHOR]

In order to deal with the challenges in establishing a high input voltage high step-down auxiliary power supply (APS) for modular converters, a flyback converter utilizing series-connected silicon carbide (SiC) MOSFETs is proposed in this article. With the aid of a novel snubber circuit structure, the used series-connected SiC MOSFETs can switch with nearly perfect dynamic voltage sharing. Besides, the snubber circuit acts as voltage clamping circuit for the flyback converter, so voltage overshoot caused by transformer leakage inductance can be effectively controlled. Furthermore, the snubber circuit helps to power the control, gate driver, and startup circuits of the APS, leading to a reduction in system complexity and improvement in efficiency. Detailed circuit analysis and design considerations of the APS are presented. Finally, hardware of a 4 kV/120 W APS is established and experimentally verified. [ABSTRACT FROM AUTHOR]

Wide bandgap semiconductors show superior material properties enabling silicon carbide (SiC) metal-oxide-semiconductor field-effect transistors (MOSFETs) present good features on its switching speed and withstand voltage. However, the high voltage and fast switching characteristics of SiC MOSFETs also put forward new requirements for voltage measurement, that is, high bandwidth under high voltage conditions. This article proposes a new voltage divider structure and a proactive parameter design compensation network to build high voltage and high bandwidth voltage sensing circuit. This structure utilizes the characteristics that the same resistor has the same parasitic capacitance to meet the high frequency constraints of the voltage sensing circuit. The influence of parasitic parameters and load parameters on circuit performance is analyzed in detail, which provides a basis for the compensation network design. By combining the proposed voltage sensing circuit with an appropriate proactive parameter design load effect compensation network (PDCN), the withstand voltage rating of the low-voltage and high-bandwidth voltage probes can be extended to required levels. Different from other existing methods, PDCN can actively design the compensation circuit parameters and provide the optimal parameters of the compensation circuit. This lead to a smaller input capacitance than the state of the art commercial voltage probes, which will help to obtain better performance when measuring high-speed switching voltage. The performance of the voltage measurement is experimentally verified and compared by SiC-based double pulse test (DPT) circuits. [ABSTRACT FROM AUTHOR]

Wide bandgap (WBG) semiconductor devices are developing rapidly due to their superior performance compared to traditional silicon-based devices. However, the packaging technology of traditional devices has limited the application of WBG semiconductor devices because of the challenges in electrical insulation. The complex environment of high blocking voltage, high frequency, and high temperature is the major reason for insulation failure of encapsulation structure. Therefore, in this article, an epoxy resin composite with nonlinear conductivity is proposed to be used as a coating to improve the electric field distribution of high-voltage high-power IGBT modules. First, an electrical field simulation model was built considering the thermal stress. It was found that the electric field in high temperature was improved compared with that in room temperature due to the temperature-dependent conductivity of silicone gel. Nevertheless, the risk of insulation failure still exists. After the application of nonlinear conductivity materials (NCMs) coating, the maximum electric field at the triple junctions and the ratio of electric field distortion in high field areas were significantly decreased. Further analysis showed that the optimization ratio of electric field increased with the increase of the blocking voltages or power losses in the IGBT chip. The results have demonstrated that the NCMs can reduce the maximum electric field in the IGBT encapsulation structure by 73% under the operating conditions of 120 W 10 kV. Partial discharge (PD) tests show that the partial discharge initial voltage (PDIV) of the substrates with NCM coating is increased by 33% compared with the normal encapsulation structure and the coating significantly inhibits the growth of electric trees. The presented results indicate that the NCMs have the potential to improve the insulation performance of high-voltage high-power IGBT modules. [ABSTRACT FROM AUTHOR]

Recycled polyester textile fibers stemming from waste polyester material have been applied in the textile industry in recent years. However, there are few studies focusing on the evaluation and comparison of the environmental impacts caused by the production of virgin polyester textiles and recycled polyester textiles. In this study, the carbon footprint and water footprint of virgin polyester textiles and recycled polyester textiles were calculated and compared. The results showed that the carbon footprint of the virgin polyester textiles production was 119.59 kgCO2/100 kg. Terephthalic acid production process occupied the largest proportion, accounting for 45.83%, followed by polyester fabric production process, ethylene production process, paraxylene production process, ethylene glycol production process and polyester fiber production process. The total carbon footprint of waste polyester recycling was 1154.15 kgCO2/100 kg, approximately ten times that of virgin polyester textiles production. As for the water footprint, it showed that virgin polyester fabric production and recycled polyester fabric production both had great impact on water eutrophication and water scarcity. Chemical oxygen demand caused the largest water eutrophication footprint, followed by ammonia-nitrogen and five-day biochemical oxygen demand. The water scarcity footprint of virgin polyester fabric production and recycled polyester fabric production was 5.98 m3 H2Oeq/100 kg and 1.90 m3 H2Oeq/100 kg, respectively. The comprehensive evaluation of carbon footprint and water footprint with the life cycle assessment polygon method indicated that the polyester fabric production process exhibited greater environmental impacts both for virgin polyester and recycled polyester. [ABSTRACT FROM AUTHOR]

This letter proposed a novel high-current planar inductor with cooling fins based on 3-D printing and its copper winding is 3-D printed by using selective laser melting technology. The 3-D-printed winding is designed for high-current applications based on 3-D space and can work as both winding and cooling fins. Compared with conventional printed circuit board (PCB) planar inductor, the proposed planar inductor not only has better performance, such as low dc resistance (DCR), ac resistance, and temperature rise, without volume increasing, but also has the superiorities of conventional PCB planar magnetics, such as ease of manufacture and controllability. To verify its performance, a 100-A-output buck converter using the proposed inductor was fabricated and compared with another identical buck converter using a conventional PCB inductor with the same size. The DCR of the proposed inductor is almost one-fifth of the PCB inductor. Besides, the efficiency of the buck converter with the proposed inductor is always over 0.5% higher than that with PCB inductor under different loads and its maximum efficiency is nearly 1% higher at light load. Furthermore, the maximum temperature rise of the proposed inductor is 26.8 $^{\circ }$ C under full load, only one-third of the PCB planar inductor. In other words, the proposed inductor can work well under 100-A current, whereas the traditional PCB inductor cannot due to too high temperature (103.8 $^{\circ }$ C). [ABSTRACT FROM AUTHOR]

The on-board low-voltage dc–dc converter (LDC) in electric vehicles (EVs) is used to connect the high-voltage battery with the low-voltage auxiliary system. With the advancement of auxiliary equipment in EVs, the output current of the LDC can be hundreds of amperes, which will cause high-conduction loss and severe thermal concern. In this article, a high-efficiency high-power-density on-board LDC is presented. To reduce current stress and improve efficiency, three-phase interleaved LLC dc–dc converters are paralleled to provide 270 A load current. Synchronous rectifier is used to reduce secondary conduction loss. zero-voltage-switching (ZVS) turn-on of primary switches and ZCS turn-off of secondary switches are achieved, thus switching loss can be reduced significantly. Moreover, phase-shedding technology is used to improve light load efficiency. Switch-controlled capacitor (SCC) technology is used to achieve accurate load current sharing among the three phases, which protects the devices against high-current stress, reduces the conduction loss, and improves the reliability of the system. As SCC switches achieve ZVS turn-on and turn-off by its nature, the loss of the SCC circuit is of less concern with regard to the rated output power. In addition, GaN HEMTs are used in the primary side to improve the power density and eventually help achieving light weight. A 3.8-kW (14 V/270 A) LDC prototype is developed and tested. Experimental results show good current balancing among the three phases. A peak efficiency of 96.7% at 140 A load and a full load efficiency of 95.8% are achieved with 3 kW/L power density and 1.5 kg weight. [ABSTRACT FROM AUTHOR]

Transfer efficiency of a wireless power transfer (WPT) system is tightly related to the load, which varies greatly in a wide range during the charging process. Generally speaking, dual-sided control strategies are commonly applied to overcome the load variation and improve system efficiency. However, the system may suffer from hard switching, high control complexity, and auxiliary dc/dc converters. In this article, a dual-sided control strategy based on mode switching is proposed to approach an optimal load impedance, zero-voltage switching of all mosfets in WPT system, and a required output. In this control strategy, the output voltage of the inverter is adjusted in a wide range by switching the operation mode of the inverter to approach the optimal load impedance. The output current/voltage is regulated by the active rectifier control. Besides, a novel phase-locked method is proposed for the semi-bridgeless active rectifier control, which is simpler compared with the traditional phase-locked method. Finally, a 500-W prototype is built to verify the theoretical analysis, and the peak system efficiency of 93.9% is gained with k = 0.23. [ABSTRACT FROM AUTHOR]

Conventional half bridge class-D audio amplifier (HB-CDAA) systems typically suffer from serious bus-voltage pumping. Such a bus-voltage pumping increases the device stress and deteriorates the total harmonic distortion and noise (THD+N) of HB-CDAA. To reduce the bus-voltage pumping of HB-CDAA system, large electrolytic capacitors are usually required at the input of downstream HB-CDAA, which seriously affects the power density of HB-CDAA system. In this article, an electrolytic capacitor-free HB-CDAA system without bus-voltage pumping is proposed, which consists of a front-end bipolar-symmetric-outputs (BSO) bidirectional dc–dc converter and a downstream HB-CDAA. By providing a bidirectional current flowing path in the front-end dc–dc converter, the bus-voltage pumping of the HB-CDAA system is eliminated without using large electrolytic capacitors. Zero voltage switching (ZVS) of all switches in the front-end BSO dc–dc converter can be achieved over the full audio load range. Compared with the HB-CDAA system with a unidirectional front-end dc–dc converter, the proposed audio amplifier system benefits from high power density, low-output voltage THD+N, and voltage stress of switches. The bus-voltage pumping problem is identified, the operation of the proposed HB-CDAA system is analyzed, and the design parameters of the converter are derived to ensure ZVS of all switches. Experimental results with a 40-W prototype of the proposed audio amplifier system are presented to verify the design. [ABSTRACT FROM AUTHOR]

In this letter, a soft-switching transformerless dc−dc converter with single-input bipolar symmetric outputs (SIBSO) is proposed, which has positive and negative outputs with equal voltage amplitude and can be used in audio amplifier, bipolar symmetric auxiliary power supply application, etc. Based on the proposed bipolar symmetric outputs cells, the SIBSO dc−dc converter only requires two switches forming a half bridge circuit, and zero voltage switching (ZVS) of the two switches can be achieved over full load range. In addition, common ground of input and outputs is realized, which means the floating driver and isolated sensors are not required in the proposed dc−dc converter. The controller and drivers can be powered up by using input power supply through a simple step-down circuit, which reduces not only the cost and volume but also the complexity of the converter. The operation modes and characteristic of the proposed SIBSO dc−dc converter are analyzed. Moreover, parameter design for ZVS operation is presented. Finally, a 60-W 1-MHz switching frequency prototype is built up by using GaN high electron mobility transistors (HEMTs). Experimental results shown that bipolar symmetric outputs are obtained with common ground of input and output, and peak efficiency of 95.8% and power density of 154 W/in3 are achieved. [ABSTRACT FROM AUTHOR]

The gallium nitride high electron mobility transistors (GaN HEMTs) are a superior candidate for the new-generation power electronics systems with higher efficiency and power density. However, due to the unique reverse characteristics, the reverse voltage drop of GaN HEMTs is much higher than that of diode. The deadtime loss in GaN-based bridge converters will be comparable to switching losses if the deadtime is not optimized. To optimize the deadtime for higher efficiency, this article proposes an accurate analytical model of GaN HEMTs, including circuit's parasitic inductances, the nonlinear capacitances, the unique reverse characteristics, etc. Taking a GaN-based synchronous buck converter as the example, the proposed model is realized, which fully uses the datasheet to avoid additional experiments. In order to accurately measure the switching current for validation, a novel parasitics-based current measurement method is proposed. The proposed model is verified by simulation in LTspice and experiment, and good agreement is shown. Based on the accurate analytical model, the deadtime is optimized for different load currents to improve the efficiency within the full load range. Compared with the fixed deadtime of 15 ns, the increase of efficiency can be up to 8%. This work will promote the high-frequency application of GaN HEMTs. [ABSTRACT FROM AUTHOR]

The synchronous rectifier (SR) turn-off time should be accurately controlled to achieve zero voltage switching (ZVS) while minimizing circulating current in pulsewidth modulation converters operating at critical conduction mode. Traditionally, the zero-crossing of the inductor current needs to be detected, and the optimal SR turn-off time is set with reference to the zero-crossing signal. However, problems such as nonlinearity and time delay need to be dealt with, and these make the tuning process very time-consuming at high frequencies. Moreover, accurate zero-current detection is also challenging at high frequencies. This letter proposes an adaptive SR turn-off time tuning method for MHz power converters. The body diode conduction of active switch is detected to adjust the SR turn-off time. With the proposed method, the SR turn-off time can be tuned under various working conditions so that ZVS is achieved while circulating current is minimized. The proposed scheme is easy to implement and not sensitive to switching noise at high frequencies. A 500-W gallium nitride based boost converter is built to verify the proposed method, and the peak efficiency reaches 99% at 1 MHz. [ABSTRACT FROM AUTHOR]

Series-connection of silicon carbide (SiC)-MOSFETs is an attractive method to achieve a high-voltage and fast-switching power semiconductor switch. In order to deal with the unequal voltage sharing problem in such series connection method, a novel active voltage clamping circuit topology is proposed in this letter. The maximum drain–source voltages of the series-connected SiC-MOSFETs are clamped by individual clamping capacitors; therefore, high reliable switching of the power semiconductors is guaranteed. Besides, the accumulated energy in the clamping capacitors can be actively transferred back into the power supply through a simple gate drive signal adjustment algorithm; thus, the induced clamping circuit loss can be effectively suppressed. The proposed active clamping topology has been experimentally verified in a half-bridge inverter with four SiC-MOSFETs connected in series. [ABSTRACT FROM AUTHOR]

Private electric vehicles (PREVs) and electric taxis (ETs) are two of the most common electric vehicles (EVs) in the cities. It is important to regulate the charging load file of PREVs and ETs, which has a significant impact on the power grid. Most of the existing works optimize the charging load profiles of PREVs and ETs separately since their charging behaviors are different. However, the separated optimization methods may not find out the optimal profile of the total charging load. To address this problem, in this article, we propose a two-stage integrated scheduling strategy, which can achieve a desired load profile of PREVs and ETs. In the first stage, according to the charging models of PREVs and ETs, we formulate an integrated optimization problem to determine the optimal feasible total load profile and the respective optimal load profiles of PREVs and ETs. In the second stage, we formulate two 0–1 optimization problems, respectively, which aim to select PREVs and ETs in the most need of charge to track the reference load fed from the first stage. We propose a generic algorithm to solve the two problems, which has fast convergence speed and requires low data size of communication. Finally, the simulation results validate the effectiveness of the proposed algorithm. Moreover, we demonstrate that proposed integrated scheduling strategy performs better than the separated scheduling strategies. [ABSTRACT FROM AUTHOR]

Multichip SiC power modules with Kelvin-source connection are popular in applications with large capacity and high switching frequency. However, dynamic current imbalance among paralleled dies due to asymmetric layout limits the available capacity. Thus, this article proposes a method to mitigate the mismatched dynamic current by adjusting the connection points of bonding wires and copper traces. The response surface models and nonlinear constrained optimization algorithms are introduced for the first time to help determine the optimized positions for the connection points. By this method, the dynamic current imbalance can be well suppressed under various working conditions. Besides, the method is cost-efficient and well compatible with the conventional manufacturing technologies because there need no additional efforts but some modifications on bonding wires. At first, the optimization guidelines are obtained after analyzing the mechanism of dynamic current imbalance among paralleled SiC MOSFETs with Kelvin-source connection. Based on the optimization guidelines and response surface models of parasitic inductance, the dynamic current sharing problem can be transformed into a nonlinear constrained optimization issue in mathematics. According to the solution of the mathematic problem, the optimized positions for connection points of bonding wires and copper traces can be determined. Finally, some simulations and experiments are conducted to verify the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

Current sense resistor (CSR) is widely used due to cost and integration considerations in industrial applications. However, when CSRs are used to sense transient currents caused by power device switching, especially fast-switching silicon carbide (SiC) metal-oxide-semiconductor field-effect transistors (mosfets) with high di/dt, even a tiny parasitic inductance in CSRs bring a significant impact on its sensing performance. This article proposes a low-cost well-performance and easy-to-design current sensing circuit that uses the CSRs and an LR compensation network (LRCN) to compensate for the effect of parasitic inductance on transient current sensing. In order to support the parameter selection of the LR network, the effects of parameters such as parasitic capacitance, parasitic inductance, and loads on the performance of the proposed current sensing circuit are analyzed in detail. Meanwhile, a parasitic inductance measurement method that only needs passive probes is proposed to measure and calculate the parasitic inductance of CSRs. This circuit can not only sense the transient current on the printed circuit board level but also observe the transient current on the oscilloscope through a coaxial cable connection. Finally, experimental studies under an inductive load double pulse test setup with SiC mosfets are carried out to verify the validity and feasibility of the proposed transient current sensing circuit. Only a high self-resonant frequency inductor and a surface mounted device resistor are needed to form the LR network to fully compensate the effect of parasitic inductance on CSRs. [ABSTRACT FROM AUTHOR]

Power semiconductor switches are usually connected in series to achieve higher blocking voltage. However, the series-operation of semiconductor devices is not easy due to unequal voltage sharing. In comparison with silicon (Si) devices, series-connecting silicon carbide (SiC) devices are even more challenging due to their ultrafast switching speed. In this article, a novel snubber circuit topology with energy recovery capability is proposed to control the voltage sharing of series-connected SiC mosfets. The snubber circuits operate with a self-balancing technique; thus, the required control and sensing circuits are simple. The proposed method maintains the snubber capacitor voltage nearly constant, so the snubber capacitors are not fully discharged during the devices on-state. Besides, excess snubber energy can be transferred back to the dc bus, so the induced snubber loss is minimal. Experimental results show the effectiveness of the proposed snubber circuit topology in a half-bridge inverter with four SiC mosfets connected in series. [ABSTRACT FROM AUTHOR]

Tight voltage regulation and high efficiency are fundamental objectives of wireless power transfer systems (WPTSs) as power supplies. Although the well-established impedance matching control attempts to achieve high efficiency, the associated extra dc–dc converters or hard switching of converters in WPTSs reduce the overall system efficiency, particularly for high-power applications. In this article, under zero voltage switching (ZVS) conditions, the minimum power loss point is derived and proved in detail with different ZVS angles. Moreover, a joint control with variable ZVS angles (JC-VZA) is proposed to ensure ZVS of all switches and achieve the required output, simultaneously. This control scheme is implemented by use of controllers in both sides of WPTSs, which adjust their respective ZVS angles for dynamic efficiency optimization. Under ZVS conditions, the proposed JC-VZA features an optimal amount of reactive power that achieves the minimum total power loss by significantly reducing the switching loss. As a result, the experimental results obtained from our WPTS prototype verify its superiority. With a coupling coefficient k of 0.2 or 0.15, the maximum efficiency reaches 96.8% or 95.0% under the power rating of 288 W (rated load) as well as 92.4% or 88.7% in the case of light load (9% of 288 W). [ABSTRACT FROM AUTHOR]