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Due to the input current dead zones, the buck power factor correction converter has to set a fixed output voltage for a tradeoff between the total harmonic distortion (THD ${_\mathit{i}}$) and efficiency. Thus, many converter-cell integrated buck-type converters have been proposed to eliminate the dead zones, which unfortunately deteriorate efficiency due to the extra components.This article proposes a group of bridgeless buck-type integrated topologies. Then, a dead-zone-free bridgeless buck-type topology with a wide output voltage range is targeted for further study. The studied converter operates in the buck+flyback mode and can automatically change to flyback mode when the dead zones occur, which only requires a simple control. Moreover, an integrated transformer based on an E-E core is investigated to reduce cost and volume. The bridgeless operation modes are introduced, followed by the PF and THD ${_\mathit{i}}$ analysis to optimize its performance. Prototypes are built and tested, which confirm the effectiveness of the converter and the integrated magnetic. [ABSTRACT FROM AUTHOR]

Given the telecom base transceiver station (BTS) load mission profiles, a mixed conduction mode (MCM) control for a bridgeless boost PFC converter (IPOS boost) is proposed to mainly improve its power factor and reduce the input current total harmonic distortion (THD ${_{\mathit{i}}}$) in the light-load conditions. The principle of the MCM control and the efficiency analysis are introduced. Then, the experimental verification is performed to show the control effectiveness and performance improvements. Furthermore, a mission profile-based reliability assessment for the PFC converter is presented to analyze the IPOS boost under the classical average current (AVC) control and the proposed MCM control, along with its conventional boost counterpart under the AVC control. Considering the measured efficiency data and BTS typical mission profiles in a rural area, the analysis results indicate that given 20 years of operation, the accumulated failure of the IPOS boost under the AVC controls is 0.27%, and is further decreased to 0.24% by just the software update with the proposed MCM control. By contrast, the accumulated failure of the conventional boost counterpart under the AVC control is 2.06%, much higher than the IPOS boost. [ABSTRACT FROM AUTHOR]

Compared with conventional power factor correction topologies, although dual-converter cell-based bridgeless topologies usually have higher efficiency, most of them suffer from high component counts. Thus, this article proposes general topology simplification methods for these topologies. Besides, several selected converter cells are exemplified to show the specific topology simplification processes, and the performance of the resultant simplified topologies is reviewed. Meanwhile, based on the same design specifications, in order to provide an unbiased quantitative topology comparison in terms of power loss, cost, and volume, this article introduces a consistent component database-based design procedure with electrical, thermal, and cost models. As case studies, the conventional and two selected bridgeless buck–boost-type topologies are compared by following the design procedure. The comparison results are analyzed to provide a reference for topology selection. Three prototypes are built and tested to verify the theoretical analysis. [ABSTRACT FROM AUTHOR]

This article introduces two general ways to derive single-phase bridgeless power factor correction (PFC) topologies and then, 15 accessible bridgeless topologies are derived based on the configuration of different basic types of dc–dc converter cells. Although the majority of the topologies have been previously proposed, other possible research points are reviewed. Besides, a consistent component sizing procedure with electric, thermal, and cost models is applied to conduct the performance benchmarking of these PFC topologies in terms of power loss, volume, and cost. Three boost-type PFC topologies are chosen as examples to demonstrate the procedure and the corresponding benchmarking results with both theoretical analyses and experimental verification. Finally, mission profiles of one specific application are introduced to show the material cost payback period of adopting one modified bridgeless boost topology instead of conventional one in different scenarios. [ABSTRACT FROM AUTHOR]

Compared with constant duty cycle-controlled discontinuous conduction mode (DCM) boost power factor (PF) correction (PFC) converter, constant duty cycle-controlled quadratic DCM–DCM boost PFC converter features with much lower second-order line frequency output voltage ripple, and however, it suffers from low PF. To increase PF of quadratic DCM–DCM boost PFC converter, a variable duty cycle control technique for quadratic DCM–DCM boost PFC converter is presented in this paper. An approximation equivalent for the variable duty cycle is employed to simplify the implementation circuit. The corresponding expressions of PF and output voltage ripple are analyzed. For input voltage range of 100–240 Vac, quadratic DCM–DCM boost PFC converter with variable duty cycle control benefits with very high PF, and tradeoff between PF and output voltage ripple of this converter is analyzed. Experimental results from 100-W prototypes are given to verify the theoretical analysis. [ABSTRACT FROM PUBLISHER]

Rationale: Atmospheric pressure interface multi‐reflection time‐of‐flight mass spectrometry (API‐MRTOF‐MS) has the potential to be a rapid and high‐resolution analytical tool for versatile applications in chemistry, biology, environmental science, and medicine. Methods: The ions were reflected in a mass analyzer via electrostatic mirrors and folded flight path. Therefore, flight distances were significantly increased. The ion flight path of the API‐MRTOF‐MS was extended from meters to over 1 km, and the mass resolution was increased. Furthermore, the mass analysis could be completed at around 10 ms due to the rapid response of TOF‐MS. Results: A high‐resolution API‐MRTOF‐MS approach is successfully developed in this study. The mass resolution could achieve 116 050 (full widths at half maximum [FWHM]) for Cs+ ions using an atmospheric pressure electrospray ionization within a total TOF of only 18 ms. An ion transmission efficiency of over 50% was achieved after 600 cycles. Conclusions: The analytical performance of the newly developed API‐MRTOF‐MS demonstrated that it is suitable for high resolution and rapid analysis in many fields. [ABSTRACT FROM AUTHOR]

Pulsewidth modulation (PWM) strategies, including continuous PWM (CPWM) and discontinuous PWM (DPWM), have been efficiently applied in the three-phase voltage source converters (VSCs). In the three-phase VSCs, dead-time distortion is inevitable. The characteristics of the dead-time distortion of three-phase VSCs with CPWM strategies have been studied extensively, whereas those of DPWM strategies have not been studied in detail. In this article, a comparative analysis of the dead-time distortion of CPWM strategies and DPWM strategies is conducted. Furthermore, the improvement of the PWM strategies to mitigate dead-time distortion is presented. The improved PWM strategies inject the compensation signals to the modulation signals to reconstruct the dead-time voltage error, which can significantly reduce the dead-time distortion of various PWM strategies. Experimental tests are conducted and the experimental results are provided to verify the analysis results of the dead-time distortion of DPWM strategies and the improved PWM strategies. [ABSTRACT FROM AUTHOR]

The dead-time between the switches in the upper and the lower bridge of voltage source PWM converters produces input current distortion, called as dead-time distortion. The dead-time distortion can be compensated by trapezoidal voltage. The conventional trapezoidal voltage compensation method (TVCM) only controls the angle of the trapezoidal voltage. By the control of the angle and amplitude of the trapezoidal voltage simultaneously, an improved TVCM is proposed to further reduce the dead-time distortion. The experimental results are provided to verify the analysis results. [ABSTRACT FROM AUTHOR]

A dual-stage asymmetric ion funnel (DAIF) interface has been designed to remove the bottleneck in ion transmission from atmospheric ionization to the vacuum chamber. This leads to increased sensitivity and improved performance of the mass spectrometer. Both ion funnels are asymmetrically constructed, with a precisely calculated 7 mm radial offset in the ion path. This accelerates the separation of ions from the neutral stream, reduces contamination, and enhances the flow field and vacuum system. The performance of the DAIF interface was investigated through numerical simulations and experimental tests, utilizing the Hexin API-5000 TOFMS as our experimental platform. The results indicate that the asymmetric ion funnel has a powerful desolvation capability, achieving a high transmission efficiency of 87.9%. The novel DAIF interface enhances sensitivity by an order of magnitude. In addition, the robustness of the instrument can be improved by efficiently removing neutral molecules and contaminants from the DAIF. These features make DAIF suitable for various MS systems and ionizations. [Display omitted] • Dual-stage asymmetric ion funnel interface. • High transmission efficiency. • Efficiently removing neutral molecules and contaminants. [ABSTRACT FROM AUTHOR]

In this work, supersonic fine particle bombardment (SFPB) was applied to modify surface of TC11 alloy and its impacts on microstructure and fatigue properties were systematically studied. The modified surface owned a nanoscale grain structure and a compressive residual stress with an amplitude of −196 MPa. The depth of hardened layer was about 300 μm. Afterwards, high-cycle fatigue behavior of SFPB modified alloy at −30 °C, 25 °C and 150 °C was studied, and the fracture surface, microstructure evolution, residual stress relaxation and microhardness of Ti alloy were characterized. The results show that the fatigue strength of the alloy is significantly improved by SFPB, and the fatigue strength decreases with the testing temperature. The deformation-induced martensite appears in the subsurface structure of Ti alloy tested at 25 °C and 150 °C, and the amount of deformation-induced martensite increases with the fatigue loading temperature. The compressive residual stress field induced by SFPB is relaxed in different degrees during fatigue loading. The degree of residual stress relaxation is the lowest under fatigue loading at 150 °C due to low cycle life. Mechanisms leading to the microstructural evolution and mechanical property variations were also proposed. • Surface nanocrystallization of TC11 alloy can be induced by SFPB. • SFPB can improve the fatigue strength of the TC11 alloy at different temperatures. • Deformation-induced martensite appears in the subsurface layer at 25 °C and 150 °C, but not at −30 °C. • Relaxation degree of residual stress is the lowest after fatigue loading at 150 °C. [ABSTRACT FROM AUTHOR]