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Background: In areas where malaria has been eliminated, delayed care-seeking and diagnosis of imported malaria are constant threats. Therefore, this study aimed to describe the profile and determinants of delayed care-seeking and diagnosis among patients with imported malaria in China. These new findings may provide a basis for developing novel approaches to prevent the re-establishment of malaria. Methods: This retrospective study assessed surveillance data obtained from 2014 to 2021 in the Chinese provinces of Anhui, Henan, Hubei, and Zhejiang, and the Guangxi autonomous region. Epidemiological characteristics were analyzed using descriptive statistics. Furthermore, factors associated with delayed care-seeking and diagnosis among imported malaria cases were identified using multivariate logistic regression. Results: Overall, 11.81% and 30.08% of imported malaria cases had delays in seeking care and diagnosis, respectively. During the study period, there was a decreasing trend in the proportion of imported malaria cases with delayed care-seeking (χ2=36.099, P＜0.001) and diagnosis (χ2=11.395, P=0.001). In multivariate analysis, independent risk factors associated with delayed care-seeking include provinces (Guangxi as reference), consultations in high-level facilities for the first medical visit, infections with non-falciparum species, and older age. However, provinces (Guangxi as reference), the purpose of traveling (labour as reference), and infections with non-falciparum species increased the risk of delayed diagnosis. Delayed care-seeking (adjusted odds ratio: 1.79, p=0.001) and diagnosis (adjusted odds ratio: 1.62, p=0.004) were risk factors for severe disease development. Conclusions: Based on this study’s findings, we strongly advocate for improved access to quality healthcare to reduce the rate of misdiagnosis at the first visit. Infections caused by non-falciparum species should be highlighted, and more sensitive and specific point-of-care detection methods for non-falciparum species should be developed and implemented. In addition, education programs should be enhanced to reach target populations at risk of malaria infection. All these factors may reduce delayed care-seeking and diagnosis of imported malaria.

This article first develops a radiated electromagnetic interference (EMI) model for a gallium nitride (GaN) integrated circuit (IC)-based active clamp flyback converter. Important capacitive couplings, which play a big role in the radiated EMI, are identified, extracted, and validated in the converter. The radiated EMI model is improved to characterize the impact of capacitive couplings. Based on the improved model, techniques to reduce capacitive couplings and the radiated EMI are proposed and experimentally validated.

Remaining useful lifetime prediction and extension of Si power devices have been studied extensively. Silicon carbide (SiC) power devices have been developed and commercialized. Specifically, SiC mosfet s have been utilized for the next generation high-voltage, high-power converters with smaller size and higher efficiency, covering various mainstream applications, including photovoltaic systems, electric vehicles, solid-state transformers, and more electric ships and airplanes. However, the SiC-based devices have different failure modes and mechanisms compared with Si counterparts. Therefore, a comprehensive review is critical to develop accurate lifetime prediction and extension strategies for SiC power converter systems. The SiC power device component-level failure modes and mechanisms are first investigated. Different accelerated lifetime tests and component-level lifetime models are then compared. Power converter system-level offline lifetime modeling techniques and software tools are further summarized. Besides, the SiC power converter condition monitoring strategies and health indicators are surveyed. The online measurement challenges are also studied. Furthermore, the system-level lifetime extension strategies are reviewed. By integrating device physics, statistical modeling, reliability engineering, and mechanical engineering with power electronics, this article is intended to provide a comprehensive overview, address existing challenges, and unfold new research opportunities regarding the SiC power converter real-time lifetime prediction and extension.

China was certified malaria-free on June 30, 2021. However, imported malaria continuously threatens the effort to prevent re-establishment of malaria in China.Measures such as international travel restrictions, entry quarantine, and screening in fever clinics during the coronavirus disease 2019 (COVID-19) period were associated with a significant decrease of imported malaria cases in Anhui Province, a higher proportion of non-It is necessary to be vigilant about imported malaria during the COVID-19 epidemic, especially for non

This article proposes a three-dimensional heterogenous-integrated (3DHI) switchable bandpass filter bank with two independent wideband filter channels that cover 26–40 GHz and 32.5–40 GHz, respectively. An accurate wafer-level process with a high hollowed ratio of the applied 8-inch high-resistivity-silicon (HR-Si) interposer wafers is presented to form both compact filter channels. Above the interdigital filter patterns fabricated on the bottom interposer wafer, deep cavities are etched in the cap interposer wafer to improve the quality factor of the filter bank. Besides the cavities, the cap interposer wafer is 35% hollow inside, which two bare dies of GaAs single-pole double-throw (SPDT) switches and two thin film resistors are attached to the bottom interposer after the wafer-to-wafer (W2W) bonding. To ensure good out-of-band performance, a 3D EM co-simulation of the switch layout at the chip level and filter patterns at the package level is applied. Measurement results show that the switchable filter bank achieves a high isolation of 50 dB and a competitive shape factor (BW30dB/BW3dB) of about 1.3. In addition, the size of the switchable filter bank is only 7.0 mm × 3.5 mm × 0.6 mm, and the weight is only 0.1 g.

Imported malaria in Anhui Province, China, remains a significant public health issue with frequent reporting of severe and fatal cases, partly because of globalization and increased international communication. A retrospective evaluation using surveillance data from 2012 to 2018 was conducted to draw lessons on diagnosis of imported malaria. Epidemiological characteristics, together with diagnostic information, were analyzed using descriptive and comparative statistics. Simultaneously, blinded rechecking of malaria blood slides was performed at general hospitals in Anhui Province in 2018. The results showed that, in their first medical visits, 238 (28.2%) of 844 imported cases were not correctly diagnosed. Notably, the proportion of patients who were misdiagnosed at the first clinic visit was 104/120 (86.7%) at private and village clinics, and 41/81 (50.6%) at primary hospitals. The species identification rates for Plasmodium falciparum, Plasmodium vivax, Plasmodium ovale, and Plasmodium malariae were 85.2%, 66.7%, 23.2%, and 32.3% (χ(2) = 224, P < 0.001), respectively. Nearly 7% of cases lacked laboratory evidence and were classified as presumed cases. Our findings suggest that physicians and health care providers, especially those at the primary level, lacked the awareness of diagnosing imported malaria. The training of physicians in malaria diagnosis needs to be enhanced. In addition, polymerase chain reactions (previously only carried out at the provincial level) should be performed at municipal CDC for rapid species identification, thereby guiding clinical treatment.

In this paper, instantaneous pulse power compensator (IPPC) method is proposed to achieve power pulsation decoupling function for single-phase inverter applications. A smaller capacitor is placed in series with the traditional dc-link capacitor, and this smaller capacitor voltage is controlled using pulse currents to cancel out the dc-link voltage ripple. Unlike twice-line-frequency power decoupling method, the proposed IPPC method can compensate the pulsating power with all the orders harmonics on the dc-link line, not only the second-order component. Both modeling and simulation results show that IPPC method can achieve nearly zero voltage ripple for the dc-link capacitor since the pulse current is fully compensated. Whereas twice-line-frequency power decoupling method has limit in voltage ripple reduction, especially in small dc-link capacitance conditions. The experimental results based on a full-bridge topology decoupling circuit and a single-phase inverter application show consistent results with simulation results. A 16% reduction of the prototype size, i.e., 16% higher power density with only ∼1% efficiency penalty can be achieved by the proposed IPPC method when compared to the second-order power decoupling method.

This paper presents a genetic algorithm (GA)-based optimal configuration for multisegmented linear LED driver to achieve a maximized system efficiency. Based on the theoretical analysis of the turn-ON states, the system efficiency is derived and found to be highly dependent on the segment voltage and reference current parameters. GA with a fitness function of the system efficiency is introduced in detail for the case of a four-segmented LED voltage configuration. With an input voltage of 220 V (rms) and input current of $8\times $ , $10\times $ , $11\times $ , and $12\times $ reference for the four turn-ON states, the four optimal segment voltages are calculated to be 160, 80, 39, and 22 V. Saber simulation results show that the GA-based configuration can give a higher efficiency (96.5%) than other typical configurations (

BackgroundAlthough autochthonous malaria cases are no longer reported in Anhui Province, China, imported malaria has become a major health concern. The proportion of reported malaria cases caused by Plasmodium ovale spp. increased to levels higher than expected during 2012 to 2019, and showed two peaks, 19.69 % in 2015 and 19.35 % in 2018.MethodsA case-based retrospective study was performed using data collected from the China Information System for Disease Control and Prevention (CISDCP) and Information System for Parasitic Disease Control and Prevention (ISPDCP) from 2012 to 2019 to assess the trends and differences between Plasmodium ovale curtisi (P. o. curtisi) and Plasmodium ovale wallikeri (P. o. wallikeri). Epidemiological characteristics were analyzed using descriptive statistics.ResultsP. ovale curtisi and P. ovale wallikeri were found to simultaneously circulate in 14 African countries. Among 128 patients infected with P. ovale spp., the proportion of mixed infection cases was 10.16%. Six cases of co-infection with P. ovale spp. and P. falciparum were noted, each presenting with two clinical attacks (the first attack was due to P. falciparum and the second was due to P. ovale spp.) at different intervals. Accurate identification of the infecting species was achieved among only 20.00% of cases of P. ovale spp. infection. At the reporting units, 32.17% and 6.96% of cases of P. ovale spp. infection were misdiagnosed as P. vivax and P. falciparum infections, respectively.ConclusionThe present results indicate that the potential of P. ovale spp. to co-infect with other Plasmodium species has been previously underestimated, as is the incidence of P. ovale spp. in countries where malaria is endemic. P. o. curtisi may have a long latency period of >3 years and potentially cause residual foci, thus posing challenges to the elimination of malaria in P. ovale spp.-endemic areas. Considering the low rate of species identification, more sensitive point-of-care detection methods need to be developed for P. ovale spp. and introduced in non-endemic areas.

Background Although autochthonous malaria cases are no longer reported in Anhui Province, China, imported malaria has become a major health concern. The proportion of reported malaria cases caused by Plasmodium ovale spp. increased to levels higher than expected during 2012 to 2019, and showed two peaks, 19.69% in 2015 and 19.35% in 2018. Methods A case-based retrospective study was performed using data collected from the China Information System for Disease Control and Prevention (CISDCP) and Information System for Parasitic Disease Control and Prevention (ISPDCP) from 2012 to 2019 to assess the trends and differences between Plasmodium ovale curtisi (P. o. curtisi) and Plasmodium ovale wallikeri (P. o. wallikeri). Epidemiological characteristics were analyzed using descriptive statistics. Results Plasmodium o. curtisi and P. o. wallikeri were found to simultaneously circulate in 14 African countries. Among 128 patients infected with P. ovale spp., the proportion of co-infection cases was 10.16%. Six cases of co-infection with P. ovale spp. and P. falciparum were noted, each presenting with two clinical attacks (the first attack was due to P. falciparum and the second was due to P. ovale spp.) at different intervals. Accurate identification of the infecting species was achieved among only 20.00% of cases of P. ovale spp. infection. At the reporting units, 32.17% and 6.96% of cases of P. ovale spp. infection were misdiagnosed as P. vivax and P. falciparum infections, respectively. Conclusion The present results indicate that the potential of P. ovale spp. to co-infect with other Plasmodium species has been previously underestimated, as is the incidence of P. ovale spp. in countries where malaria is endemic. P. o. curtisi may have a long latency period of > 3 years and potentially cause residual foci, thus posing challenges to the elimination of malaria in P. ovale spp.-endemic areas. Considering the low rate of species identification, more sensitive point-of-care detection methods need to be developed for P. ovale spp. and introduced in non-endemic areas.

In this work, avalanche ruggedness and failure mechanism of SiC MOSFET in single-pulse Unclamped Inductive Switching (UIS) test are investigated and compared with Si IGBT. The experimental results show that SiC MOSFET can handle ∼20% higher avalanche energy at the same current density, and ∼50% higher current density at the same amount of energy. As SiC device has 5× smaller chip size, the advantage will disappear when comparison is performed with avalanche current. To improve the avalanche current capability of SiC MOSFET, failure mechanisms are analyzed. At first, the junction temperature is calculated with V-T model and thermal model, from which a linear dependence of temperature on avalanche current is revealed. Then, the probability of parasitic BJT turn-on is modeled analytically with the base-to-emitter resistance/voltage, which is found to be highly dependent on the p+ ohmic contact resistance (ρc) and base doping concentration (NB) designs of the device. Based on the modeling results, at the peak junction temperature 650 K in UIS test, the BJT turn-on can already be triggered for SiC MOSFET. The failure trigger temperature can be raised with a higher NB and lower ρc design, thus the avalanche current capability can be increased accordingly. On the other hand, with a much deeper p+ body structure design, the Si IGBT can prevent the BJT latch-up failure. Based on the failure analysis, a trench source structure of SiC MOSFET is proposed to further improve the avalanche capability for smaller chip size design.

This paper investigates radiated electromagnetic interference (EMI) causes and solutions in high-frequency active-clamp flyback (ACF) using GaN ICs. GaN devices enable high-frequency operation which shrinks the passive component size and can potentially be more efficient. However, the increased spectrum of radiated EMI is a concern with a lack of readily-available solutions. This paper analyzes noise mechanisms by studying waveform and spectrum compositions, identifying major noise contributors. Near field couplings of the cable-converter electric couplings are identified as inducing the CM noise and bypassing the CM choke. This paper develops models to characterize the near field coupling effects on the radiated EMI. Noise reduction techniques including a shielding and grounding technique, a CLC pi-type CM filter are proposed and verified. Experimental verifications are performed on a GaN IC-based ACF power adapter and radiated EMI is brought into compliance.

Achieving high efficiency and high power density features of intermediate bus converter (IBC) in data center application is very critical. This paper proposes a nonisolated switched-tank dc–dc converter (STC) to meet the high requirement of IBC. The proposed STC has fixed voltage conversion ratio. Theoretical analysis provides the guideline for designing resonant tank and nonresonant tank as well as selecting proper deadtime for the proposed circuit. With resonant operation feature of the proposed circuit, zero current switching is realized on all switching devices to help the high-efficiency operation of the proposed converter. Through the proposed design methodology in this paper, power loss on switching devices and planar inductors can be minimized. In addition, detailed power loss analysis and breakdown provide hints for further efficiency improvement. Simulation has been performed to validate the operating principle of the proposed STC. A designed 6x STC (450 W nominal/600 W maximum) based on eGaNFETs is demonstrated. With 54 V typical input voltage, the output of the 6x STC is 9 V. The GaN-based prototype achieves a peak efficiency of 98.55%. Also, it achieves 97.18% efficiency and 750 W/in3 power density at 450 W.

Background In the Anhui province, China, efforts to halt local malaria transmission were successful, with no endemic cases reported since 2014. Contrastingly, imported malaria cases are still being reported, indicating a disease reintroduction risk after years of eradication. To avoid this reintroduction, rapid diagnostic tests (RDTs) were combined with microscopy methods to strengthen malaria surveillance. Herein, we aimed to evaluate the efficacy of this surveillance strategy in a field setting. Methods We conducted a retrospective study using malaria surveillance data from January 2016 to June 2020. Epidemiological characteristics and diagnostic information were analysed using descriptive and comparative statistics. The diagnostic performance of the combined toolbox (RDTs plus microscopy) was evaluated based on its sensitivity, specificity, positive and negative predictive values, and Cohen’s kappa coefficient. Results The combined toolbox displayed a higher overall sensitivity for malaria cases than that of microscopy alone (93.74% vs 89.37%; χ2 = 6.09; p = 0.14). In contrast to its high sensitivity, the combined toolbox had a specificity of 69.66%. The species identification rates of the combined toolbox for P. falciparum, P. vivax, P. ovale, and P. malariae were 83.15%, 65.00%, 42.11%, and 40.00%, respectively. Conclusions The combination of microscopy and RDTs is an effective strategy for malaria surveillance, possibly detecting more P. falciparum infections than microscopy alone. However, the specificity and ability to identify species of the combined toolbox were not optimal. Thus, monitoring malaria cases in non-endemic areas may require employing more than one diagnostic tool in surveillance strategies. Moreover, further understanding of the advantages and disadvantages of different detection methods is necessary for applying optimum combinations in the field setting.

As the demand of dc-dc converter for medium and high voltage application is increasing in recent years, more and more attention has been paid to modular multilevel converters (MMC). This paper proposes a novel transformerless MMC to achieve high-conversion-ratio DC-DC power conversion purpose. This converter can be used in Medium Voltage Direct Current (MVDC) system, as a high step-up ratio solid-state transformer (SST). The proposed converter possesses scalability, simplicity as well as inherent voltage balancing capability. No complex control algorithm is needed to balance the voltages in each submodule. By using the MMC concept, N low voltage submodules are connected in series to generate a high voltage output. The conversion ratio can be regulated by the phase-shifted control. Two kinds of submodules are outlined to build the MMC. By utilizing stray inductance distributed on wire, the bulky inductors with high power loss can be removed from the system. Resonant operation between wire stray inductance and submodule capacitors assists the converter to work under ZCS mode at high efficiency. A design example with 11-time step-up ratio is analyzed and simulated. And a 200W scaled down lab prototype with 7-time voltage step-up capability has been built to verify the proposed concept.

Cardiovascular autonomic neuropathy (CAN) is a debilitating condition occurring among diabetic patients especially those with long duration of disease. Whereas incidences and treatment of CAN has been well described for Western populations, fewer studies have been conducted among the Chinese. This study, therefore, aimed to assess the prevalence of CAN among sampled Chinese diabetic patients. Accordingly, 2,048 participants with a history of type 1 diabetes mellitus (T1DM, 73) and type 2 diabetes mellitus (T2DM, 1975) were randomly sampled from 13 hospitals. Patients’ biodata were recorded, and autonomic nervous system function tests performed to aid in the preliminary diagnosis of CAN. The final CAN diagnosis was based on the Ewing’s test in which heart rate variation (HRV) values were evaluated through deep-breathing (DB), lying-to-standing (LS), and Valsalva (V) tests. Systolic blood pressure (SBP) variation values were also evaluated through LS. In the T1DM group, 61.6% patients were diagnosed with CAN and no differences were observed in the baseline and clinical data between this group and those without CAN (P > 0.05). In the T2DM group, 62.6% patients were diagnosed with CAN and statistically significant differences were found between the CAN and non- CAN group with regards to age, duration of diabetes, metformin treatment, retinopathy, and hypertension history (P < 0.05). The most common manifestations of CAN included weakness (28.6%), dizziness (23.4%), frequent urination (19.6%), upper body sweating (18.3%), and nocturia (15.9%). Additionally, duration of disease and age were independent risk factors for CAN in T1DM and T2DM, respectively. On diagnosis, a combination of the V test + LS test provided the highest sensitivity of detecting CAN among T1DM group (sensitivity = 97.6%, AUC = 0.887) while for T2DM category, DB test had the highest sensitivity (83.6%), and maximal AUC (0.856) was found with V test + DB test. The overall prevalence of diabetes with CAN in the study was up to 63%.

A new Switched Tank Converter (STC) with Partial Power Voltage Regulation (PPVR) is introduced for electric vehicle applications. It offers a flexibly adjustable conversion ratio for a wide-range battery voltage. The unregulated stage is modularized with resonant switched capacitor converters. All device voltage stresses are equal to the input voltage. The efficient unregulated stage processes the bulk of system power and the less efficient regulated stage processes a small amount of power. Thus, high overall efficiency can be achieved. A new index called Semiconductor Loss Index (SLI) is defined as a function of semiconductor die area to evaluate different power topologies. It is helpful to analyze the impact of each switch die area, different operated output power, switching frequency, and conversion ratio on the total device power loss. With the same total semiconductor die area, the proposed converter can achieve less than 1/3 device total power loss compared with boost converter. A 4-kW 1200V output converter prototype with 200V~400V input voltage range is developed, which combines a 6 times conversion ratio STC with a PPVR buck converter. The overall full-load efficiency of designed 4-kW converter can reach to 97.71%. Simulation, prototype and experiment results are presented to verify the validity of the proposed converter.

This paper presents an in-series and in-parallel combination power decoupling method for the single-phase inverter. With basic power equation derivation, the proposed method is analyzed and compared with other methods in theory. The operating principles and the control strategy are introduced. The circuit parameters based on silicon carbide device are designed in detail, and the power losses are evaluated for the circuit. To verify the theoretical analysis, a PLECS simulation model is built. Based on the simulation results, both the proposed method and the in-series method can achieve a more than 89% reduction of the dc-link capacitance compared with the traditional inverter. Furthermore, the proposed method is superior to the in-series method, with a more than 68% reduction of the extra circuit’s capacitance. Finally, a 2-kW prototype with a size of $7.25 \,\, \times \,\, 3.6 \,\, \times \,\, 1.4$ in3 and a power density of $\sim 55$ W/in3 is developed. Compared with the in-series method, the extra capacitance can be reduced by about 64% for the proposed power decoupling method. The experimental results are almost consistent with the simulation results. The efficiency for the proposed method is higher than 95%.

Diabetic peripheral neuropathy (DPN) is the most common complication of diabetes, and its progression significantly worsens the patient's quality of life. This study investigated the prevalence and risk factors associated with DPN in a large sample of Beijing individuals with type 1 and 2 diabetes, as well as compared the diagnostic methods for DPN. A total of 2,048 diabetic patients from 13 centers in Beijing were assessed for DPN through questionnaires and examination. Patients were divided into DPN group and suspected DPN/non-DPN group. The demographic, clinical and biological characteristics between the two groups were compared. Binary logistic regression analysis was performed to identify potential variables associated with DPN in diabetic patients. The diagnostic methods for DPN were also compared. Among the 2,048 diabetic patients, 73 cases of type 1 diabetes mellitus, 1,975 cases of type 2 diabetes were included in this study. Among them, 714 (34.86%) were identified with DPN, 537 (26.22%) were suspected of having DPN, and 797 (38.92%) were identified without DPN. Patient's age, duration of diabetes, and diabetic retinopathy were the significant independent risk factor for DPN among patients with type 2 diabetes. The odds ratio (OR) was 1.439 (95% confidence interval (CI): 1.282–1.616, P < 0.001), 1.297 (95% CI: 1.151–1.462, P < 0.001), and 0.637 (95% CI: 0.506–0.802, P < 0.001), respectively. Ankle reflex, temperature sensation plus vibration sensation are the best screening test for patients with type 1 and 2 diabetes. The Youden indexes were 62.2 and 69.8%, respectively. The prevalence rates of DPN in the Chinese patients with type 1 and type 2 diabetes in Beijing were 21.92 and 35.34%, respectively. Patient's age, duration of diabetes, and diabetic retinopathy are the independent risk factors for DPN.

This paper presents a high-efficiency multiple-string linear LED driver with genetic algorithm (GA) based configuration. Compared with traditional LED drivers, linear LED drivers have advantages of high efficiency, simple structure, low cost and long life-time. To achieve the high efficiency target for multiple-string linear LED driver, the configuration of LED number in each string is a great challenge. In this paper, a method based on genetic algorithm is proposed for the string LED number (i.e. string voltage) optimization. The system efficiency analysis with input voltage and LED current is introduced. And, the GA design flowchart and interface are provided. With the developed GA algorithm code, the optimal voltage for each string can be calculated. To validate the methodology, simulations are carried out to compare the GA based configuration and other four references. The results show that the GA based configuration can achieve the highest efficiency of 96%, which is >8% higher than the other configurations under the same condition.

In this paper, an new converter that includes isolated composite resonant multilevel converter (ICRMC) that uses composite converter concept and partial power voltage regulator (PPVR) has been proposed for telecommunication application. The proposed converter can achieve high efficiency at nominal operating point since it takes minimum effort to regulate the output voltage at this point. A comparative study shows that with the proposed two operation modes of ICRMC, the proposed converter has the best capability to maintain lowest total semiconductor power stress among the existing state of the art solutions when the input voltage varies from 36V to 60V. Furthermore, zero current switching (ZCS) can be always achieved on the switching devices in ICRMC under different operating points. A 600W converter has been simulated to validate the theoretical analysis. The estimated peak efficiency can be as high as 97.65%. Fully debugged prototype and experimental results are provided in this paper.

This paper presents an instantaneous pulse power compensator (IPPC) concept to achieve ultra-high density with zero voltage ripple and zero dc-link capacitor for high-power-density single-phase inverter application. Compared with traditional 2ndorder method with various power decoupling topologies, IPPC proposed a totally new theoretical analysis from a pulse-power point of view. For dc-link voltage ripple evaluation, traditional theoretical analysis is not suitable for small-capacitance power decoupling applications, however, pulse power analysis can be applied in the whole range. From a view of state-of-the-art on power decoupling methods, a comparison figure with voltage ripple and dc-link capacitance is given to show the limitation of traditional power decoupling method and improvement of IPPC method on minimizing dc-link capacitance. One case study is presented with full-bridge topology with simulation results. Furthermore, one Silicon Carbide (SiC) based inverter and the IPPC based circuit are built. Experimental results verify the proposed idea very well.

This paper presents a smart Composite Modular Power Delivery Architecture (COMPDA). One example for this architecture is applied in DC-DC 48V to 12V data center circuit shown here. COMPDA has many good features, such as voltage clamping for all devices, low total device stress under wide range ratio. It also has good modular characteristics. Each device has the same voltage and current stress. The principle operation is that all modular cells are connected in-series to share input high voltage and in-parallel to pump output high current, which can easily achieve ultra-high power density and high efficiency. Zero current switching (ZCS) can be applied in the proposed converter. A 4X unregulated DC-DC COMPDA with ZCS is studied for data center application. Finally, a GaN based prototype is built and tested to verify the theoretical analysis. The proposed converter can achieve the peak efficiency at 98.55% under ultra-high switching frequency 253 kHz. Furthermore, another GaN based high-density 6X boost COMPDA based prototype is also presented here. The peak efficiency can achieve 98.9% at 4kW power rating.

Switched-tank converter (STC) concept can leverage the advantages of wide bandgap devices. And it is especially suitable for GaN/SiC devices. This paper presents an improved STC with separate resonant branches and on-time control method to achieve efficiency improvement. Since the STC relies on resonant operation to reach high efficiency, the problems caused by unmatched resonant tanks in different resonant loops need to be studied and solved. The study shows that in most severe case, problems caused by the unmatched resonant tanks not only compromise the efficiency of STC, but also cause undesired damage to the STC. As a result, old simple control method that uses only two complementary control signals (50% duty cycle) is not good enough anymore. Hence, an improved STC as well as adaptive on-time control method have been proposed to ensure soft-switching and high efficiency operation of the STC. A 1.2kW prototype with 6:1 conversion ratio has been built to verify the effectiveness of the proposed control method. The experimental results show that with the proposed control, efficiency of the improved 6x STC is increased by 0.5% at 900W, which means power loss is reduced by 16.77%. A peak efficiency of 98.71% has been achieved.

This paper presents an ultra-efficient composite modular power delivery architecture (COMPDA) that is able to be used for DC-DC, DC-AC, AC-DC, and AC-AC applications. The proposed architecture has very good module structure, the devices in each module have the same voltage and current stress. When it is used for high conversion ratio dc-dc applications, the device voltage stress is the same with the low voltage side, and the device current stress is the same with the low current side. Compared with the buck, flying capacitor multilevel or modular multilevel dc-dc converters, the proposed architecture has much lower total device power or current stress, which means a significant semiconductor chip area reduction. During the operation, the modules are connected in-series to sustain the high voltage and connected in-parallel to pump the high current. By properly design the resonant tank in the COMPDA, all the switching devices could achieve zero current switching or zero voltage switching. A partial power regulator could be integrated in the proposed architecture, where only a minimum amount of power needs to be processed in order to achieve the output voltage fine regulation. By properly control the operation of modules, the COMPDA can also be used as a high boost ratio DC-AC inverter or high step-down ratio AC-DC rectifier while keeping the soft-switching features, which are specially suitable for solar farm and data-center application. When apply the COMPDA to single-phase DC-AC or AC-DC applications, only a minimum amount dc-link capacitor is needed since the needs of energy storage is minimized, and there is no high voltage dc-link requirement anymore. In order to show the benefits of the COMPDA, one special unregulated case derived from the proposed architecture has been used for 48 V–8 V DC-DC data center application, which is also named switched-tank converter. Finally, a GaN based prototype is built and tested to verify the theoretical analysis. The proposed converter can achieve the peak efficiency at 98.55% under switching frequency 253 kHz and power density is ∼750W/inch3.

This paper presents a new indicator of SiC MOSFET gate oxide degradation based on Miller plateau. The physical mechanism of Miller plateau shift with gate oxide electric field is first analyzed. The relationship between Miller plateau and ambient temperature is then explored by theoretical analysis. The electro-thermal simulation is conducted in LTSpice to verify the Miller plateau shift with ambient temperature. Besides, 20 groups of High Electric Field (HEF) acceleration tests are conducted with V gs stress amplitude of 25 V, 30V, 35V, 40V and stress duration of 10, 40, 70, 85, 100 hours. 5 SCT2120AF SiC MOSEFTs from Rohm are stressed in each group. After ageing tests, the stressed devices are used to verify dynamic characteristic change in the designed double pulse test platform. After 100-hour HEF tests with 40V V gs stress, Miller plateau shift can reach up to 1.5V. Finally, comparison is made among Miller plateau, threshold voltage and gate resistor turn-on energy. Analysis shows that Miller plateau can be used as an indicator of SiC MOSFET gate oxide degradation with detectable amplitude shift as well as inherent gate driver integration and online monitoring characteristics.

This paper presents a linear light-emitting diode (LED) driver with concave current control method for low-power applications. In order to achieve a high efficiency of the linear LED driver, control methods with three different current shapes, namely, traditional flat current shape, convex current shape, and the proposed concave current shape, have been discussed and compared via theoretical analyses, numerical simulations, and experiments in this paper. It is concluded that the proposed concave current control method has the highest efficiency among these three methods for universal input voltage conditions. The operation principles and design considerations of the control method have been provided. It is verified by the experimental results that the proposed concave current control method has a 10% efficiency improvement when compared with the flat and convex current control methods. Furthermore in order to limit the peak current of the concave current for practical considerations, a revised cut-top current control method is presented by adding a limited current. Both simulation and experimental results show that a 37% reduction of the peak current is obtained for the cut-top current control method. On the other hand, a 5% improvement of the efficiency can be achieved by the revised cut-top current than flat and convex current control methods.

This paper presents comparison of GaN based switched-tank converter (STC) and traditional cascaded voltage divider (CVD) dc-dc converter for data center applications. The operation principle of two kinds of converters are presented. And simulations with Saber are both conducted to verify the proposed comparison, respectively. The system volume and efficiency are fully compared via GaN based device under the same current stress condition. It is shown that under the same condition, STC can achieve 1% higher efficiency at full load and over 2% higher efficiency at light load when compared with CVD. Furthermore, STC can achieve ∼37% power-density improvement when compared with CVD. Finally, GaN based STC prototype is built and experimental results verify the proposed idea very well.

In this paper, a resonant switched-capacitor dc-dc converter is proposed for data center application. The proposed converter possesses features such as high efficiency, high power density and light-weight. Zero current switching (ZCS) can be achieved with the resonant operation, which allows the converter operating under high efficiency. Proper switching device selection and in-depth power loss analysis on different devices have been performed to support better design of the proposed converter. Simulation results are provided in this paper to validate operation principle of the proposed converter. A GaN based prototype with nominal 450W, 54V input and 9V output has been built to verify the theoretical analysis. The maximum power rating of the designed prototype is 600W. Power density of the prototype reaches 750W/in3. When the prototype operating at 253kHz, it achieves 98.55% peak efficiency.

This paper presents a multilevel modular step-down DC-DC switched-capacitor converter that utilizes soft switching resonant operation. Previous versions of traditional multilevel modular switched-capacitor dc-dc converters (MMSCC) have a low switching device voltage rating. Moreover, capacitor voltage stress increases proportionally as the voltage conversion ratio increments. Significant advantage of proposed converter in this paper is high voltage conversion ratio with capacitor voltage stress always being only two times of the low side voltage. Additionally, the proposed circuit (SWRMC) shares all of the advantages from the (MMSCC) type converters such as soft switching, low voltage device rating, bidirectional operation, high conversion ratio, extremely high or low environment temperature operation, basic control algorithm and modular structure. In comparison with the magnetic core based converter the converter proposed in this paper is found to be superior due to the simple structure, soft switching, low conduction loss and 97% or higher efficiency.

This paper discusses a GaN based motor drive topology with a high conversion ratio and sinusoidal output voltage. This inverter topology is based on the z-source inverter and provides many benefits over the traditional three-phase inverter or traditional inverter with a DC-DC boost converter input. The semi-quasi-z-source inverter allows the input voltage source and the load to share a ground so the problem of handling leakage current is eliminated. Thanks to the high conversion ratio with the semi-quasi-z-source topology, a lower input voltage can be used to generate a desired output. The proposed topology can also take advantage of many popular modulation strategies of traditional inverters. The output of this inverter is sinusoidal so it is perfect for motor drive applications. This paper also compares the voltage and current stress of the semi-quasi-z-source inverter against a traditional inverter with a DC-DC boost converter. Simulations for a 10 kW semi-quasi-z-source inverter are also discussed at the end of this paper.

To evaluate the efficacy of bowel plication combined with early enteral nutrition (EEN) in the enhanced recovery after surgery(ERAS) of jejunal atresia (JA) neonates.Between January 2005 and January 2014, 58 neonates with JA underwent surgical treatment in Children's Hospital of Nanjing Medical University. Their clinical data, including operation procedures, ages, birth weight, concomitant diseases, age at surgery, hospital stay, total parenteral nutrition (TPN), postoperative intestinal function recovery (the time to the first oral feeding and the time to oral feeding volume reaching 150 ml·kgAccording to the surgical procedures, the 58 neonates were divided into three groups: control group(18 cases, undergoing atretic segments resection and primary anastomosis), bowel plication group(19 cases, undergoing bowel plication after atretic segments resection and primary anastomosis) and bowel plication combined with EEN group (21 cases, undergoing bowel plication combined with EEN). No significant differences of ages, birth weight, age at operation, and concomitant diseases were found among 3 groups (all P0.05). The time of hospital stay, the time to the first oral feeding, the time to oral feeding volume reaching 150 ml·kgThe bowel plication combined with EEN contributes to the early use of intestinal function, shorten the time to the first oral feeding, and reduces the use of TPN, which can improve the recovery of jejunal atresia neonates.

This paper presents a review on SiC MOSFET based 3-phase inverter lifetime prediction. The inverter-level lifetime prediction flowchart is first illustrated with the system failure rate and system Mean Time to Failure derived which integrate five in-series stresses. An overview of SiC MOSFET power module Physics-of-Failure is then presented. Following it are the step-by-step lifetime modeling comparison and summarization, including power loss analysis, thermal modeling, thermal-mechanical modeling, and damage accumulation modeling. Furthermore, cycle counting algorithms and active power cycling tests specific to SiC MOSFET are discussed. Finally, a detailed system-level thermal profile extraction from SiC MOSFET based 3-phased inverter in the hybrid electrical vehicle application is conducted. The simulation result is consistent with theoretical power loss and thermal equivalent circuit based junction temperature evaluation. Thus it can be used for further system lifetime modeling and the reference for 3-phase inverter based power cycling tests in SPWM mode.

This paper presents a novel modular multilevel switched-capacitor based resonant converter (MMSCRC) to achieve dc-dc power conversion function. In comparison to existing multilevel modular switched-capacitor circuits, the proposed switched-capacitor resonant converter (SCRC) possess voltage regulation capability. Its modular structure accomplishes voltage conversion function and proposed closed-loop phase-shift control regulates the output voltage. Meanwhile, zero-voltage switching (ZVS) operation can be accomplished. By increasing switching frequency of wide bandgap device and reducing inductance in the circuit, magnetic components can be minimized. Hence, high power density and high efficiency of the proposed converter can be achieved. This paper includes circuit operation, steady-state characteristics as well as in-depth analysis for ZVS operation. Simulation results are provided to verify the operation principle of the proposed MMSCRC. A 600W lab prototype with 6:1 conversion ratio has been built. Experimental result are also provided to validate the theoretical analysis.

This paper presents a 3-phase dc-link capacitor RMS current reduction method by increasing paralleled inverter module number for segmented traction drive. Compared with the existing 2-module paralleled system, this paper investigates increasing paralleled module number can further reduce the value of dc-link capacitor RMS current. The results show that 2 paralleled modules can reduce ∼45% and 3 paralleled modules with ∼55% reduction, 4 modules with ∼70% reduction, 5 modules with ∼75% reduction, 6 modules ∼80% reduction, respectively, with the proper interleaving scheme control. A series of PLECS simulation model are built to verify the proposed idea. Finally, 6 kW prototypes are developed with 3 modules. The experimental results are almost consistent with the simulation results.

This paper shows a combinational decoupling method to minimize dc-bus capacitance and improve power density for DC to AC applications, especially for single-phase inverters. The proposed method is combined with in-series structure and in-parallel structure together with power equations analyzed. The detailed control strategy is given. The simulations are conducted via PLECS software to prove the theoretical proposal. Furthermore, a 2kW prototype is built. The power density of this prototype is ∼55W/inch3. The decoupling capacitance is minimized ∼2/3 that of traditional series voltage compensator method. The experiments are further finished and the efficiency of the prototype is ∼ 95%. Besides, the issues for 2nd order decoupling method is investigated and an instantaneous pulse decoupling method is discussed in this paper. A brief comparison of these two methods are summarized.

This paper presents a modular multilevel dc-dc converter (MMC) with zero-current switching (ZCS) feature and its analysis for medium-voltage direct current (MVDC) applications. The main focus of this paper is analyzing the overall efficiency of the proposed MMC and experimentally verifying the theoretical analysis on operating principle. Furthermore, in order to achieve high efficiency, the proposed MMC has the capability to maintain ZCS operation at different load conditions. In this paper, the proposed MMC with maximum 200kW power output is used to perform the efficiency analysis. Simulation uses the same parameters that are used to analyze efficiency and displays waveforms when the MMC operates at 66kW. At last, a 200W lab prototype has been built. And operating characteristics of the MMC are validated through experimental results.