Models and methods for the design of isolated power converters in high-frequency high-efficiency applications

2011 - 2012Isolated power supplies design requires the achievement of overall stress, losses, cost, size and reliability trade-off. This problem is of considerable importance in modern applications of power converters, as for energy saving issues as for the achievement of high power density capabilities needed to integrate the power supply into the same boards where the system they feed is hosted. The aim of this PhD dissertation is to discuss the fundamental issues regarding the design of high-efficiency high-power-density isolated power converters, related to the transformers design and to the system-level analysis of functional and parametric correlations existing among transformers and silicon devices in the achievement of high efficiency. Transformer design is the central issue in isolated switching power supplies design. Affording a preliminary reliable investigation of possible feasible power supply designs using off-the-shelf transformers can be of great help in reducing the time to prototyping and the time-to-market. Even though many off-the-shelf transformers are available today for standard applications, many special situations occur such that the design of a custom transformer is required. New design method are needed in order to enable a wider detection and investigation of possible transformer design solutions by means of a straightforward matching between the available magnetic cores, the operating conditions of the transformer to be designed and the design constraints to be fulfilled. A critical re-examination of transformers design methods discussed in technical literature has been afforded to highlighting some common misleading assumptions which can hinder the minimization of the transformer. Thus, a new design approach has been investigated and discussed, which helps in easily identifying possible transformer solutions in critical custom designs for a given application, complying with losses and size constraints. The new method is aimed at quickly identifying possible combinations of magnetic cores and windings turns number when many possible design might be feasible and a fast comparative evaluation is needed for preliminary cores selection. Novel geometric form factors of magnetic core (Kf and Kc) have been introduced and a consequent classification procedure for magnetic cores has been obtained, showing the correlation between the characteristics of the core and the specific applications in which each type of core offers major advantages in terms of minimizing losses and/or size. A magneto-electro-thermal macro model of the transformer has been adopted in order to investigate the dependency of total transformer losses on the temperature and to analyze the temperature sensitivity of form factor constraints of magnetic cores for power loss compliance. In particular, temperature-dependent boundaries curves both for the core window area and cross-section and for the form factors Kf and Kc have been obtained, allowing quick identification of feasible design solutions, complying with all design constraints, included thermal issues. Transformers and silicon devices do inextricably share the responsibility of major losses in isolated power supplies, and the optimization of the former normally impinges the one of the latter. As a consequence, the intimate correlation among these parts need to be jointly considered regarding the way the characteristics of one device influence the losses of the other one. In order to achieve reliable comparative evaluations among different design set-up, a new versatile numerical model for commutations analysis of power MOSFETs has been developed. The model takes into account the non-linear behavior of the inter-electrode capacitances and has been conceived to work as with parameters and information contained in the devices datasheets as with more detailed models. A Modified Forward Euler (MFE) numerical technique has been specifically developed and adopted in the realization of a numerical algorithm which solves the non linear system of differential equations describing the effect of parasitic capacitances in whatever operating conditions, in order to overcome the limitation exhibited by ODEs techniques for stiff problems in this particular application. The new MFE technique allows to compare the switching characteristics of MOSFETs with a good level of reliability and to obtain a detailed analysis of capacitive currents paths circulating between MOSFETs in half-bridge configuration during commutations. The numerical device-level model of the MOSFETs couples has been first tested in the analysis of basic non isolated synchronous rectification buck converter and then used into an integrated model allowing the analysis of Active Clamp Forward converters. It has been also demonstrated that the model adopted for the switching cell can be implemented in circuit simulators like Micro-Cap. The correlations existing between the parasitic parameters which characterize both transformer and MOSFETs and their impact on the switching behavior and the efficiency of such a conversion system can be effectively investigated by using such modeling approach, thus overcoming the limitations and unreliability of simplified analytical formulas for the prediction of the ZVS achievement. In particular, the integrated system model has been successfully used to determine the mutual constraint conditions between magnetic devices and solid state devices to achieve soft-switching, and their effects on the physical feasibility and design/selection of such power devices in order to achieve high efficiency. Experimental activities have been done to validate the methods and models proposed, through the implementation of on-line losses measurements techniques for both magnetic and solid state devices. The high switching frequency, high slew rates, high current and low leakage devices make such measures extremely sensitive to the parasitic circuit layout parameters. In order to achieve reliable measurements, non-conventional measurement techniques have been investigated based on the use of current sensing MOSFETs, and applied in the development and implementation of new measuring circuits. [edited by author]XI n.s

Women in circuits and systems (WiCAS) and young professionals (YP) at ICECS 2020.

A 'Women in Circuits and Systems' (WiCAS) event and a 'Young Professionals' (YP) event took place during the 27th Institute of Electrical and Electronics Engineers (IEEE) International conference on electronics circuits and systems (ICECS), the flagship conference for the Region 8 of the IEEE Circuits and Systems Society (CASS). The WiCAS events traditionally aim to inspire and motivate both students and young professionals in the domain of circuits and systems to have efficient roles in their professions, by meeting successful female engineers and professors, through interesting technical and professional talks in fields of interest of CASS. The YP events usually include start-ups presentation, poster and demo sessions, aiming to provide a thrilling environment for early career researchers to present their work. Joining this event, young professionals have the opportunity to learn about state of the art and most advanced activities in the area of circuits and systems, meet and interact with their peers, receive feedback from internationally well-known experts in the CASS domain from both academia and industry

An enhanced model for small-signal analysis of the phase-shifted full-bridge converter

This paper presents an in-depth critical discussion and derivation of a detailed small-signal analysis of the Phase-Shifted Full-Bridge (PSFB) converter. Circuit parasitics, resonant inductance and transformer turns ratio have all been taken into account in the evaluation of this topology’s open-loop control-to-output, line-to-output and load-to-output transfer functions. Accordingly, the significant impact of losses and resonant inductance on the converter’s transfer functions is highlighted. The enhanced dynamic model proposed in this paper enables the correct design of the converter compensator, including the effect of parasitics on the dynamic behavior of the PSFB converter. Detailed experimental results for a real-life 36V-to-14V/10A PSFB industrial application show excellent agreement with the predictions from the model proposed herein.

Precise measurements of the properties of the B-1(5721)(0,+) and B-2*(5747)(0,+) states and observation of B-+,B-0 pi(-,+) mass structures

Invariant mass distributions of B+π− and B0π+ combinations are investigated in order to study excited B mesons. The analysis is based on a data sample corresponding to 3.0 fb−1 of pp collision data, recorded by the LHCb detector at centre-of-mass energies of 7 and 8 TeV. Precise measurements of the masses and widths of the B1(5721)0,+ and B2(5747)0,+ states are reported. Clear enhancements, particularly prominent at high pion transverse momentum, are seen over background in the mass range 5850-6000 MeV in both B+π− and B0π+ combinations. The structures are consistent with the presence of four excited B mesons, labelled BJ (5840)0,+ and BJ (5960)0,+, whose masses and widths are obtained under different hypotheses for their quantum numbers

Off-label long acting injectable antipsychotics in real-world clinical practice: a cross-sectional analysis of prescriptive patterns from the STAR Network DEPOT study

Introduction Information on the off-label use of Long-Acting Injectable (LAI) antipsychotics in the real world is lacking. In this study, we aimed to identify the sociodemographic and clinical features of patients treated with on- vs off-label LAIs and predictors of off-label First- or Second-Generation Antipsychotic (FGA vs. SGA) LAI choice in everyday clinical practice. Method In a naturalistic national cohort of 449 patients who initiated LAI treatment in the STAR Network Depot Study, two groups were identified based on off- or on-label prescriptions. A multivariate logistic regression analysis was used to test several clinically relevant variables and identify those associated with the choice of FGA vs SGA prescription in the off-label group. Results SGA LAIs were more commonly prescribed in everyday practice, without significant differences in their on- and off-label use. Approximately 1 in 4 patients received an off-label prescription. In the off-label group, the most frequent diagnoses were bipolar disorder (67.5%) or any personality disorder (23.7%). FGA vs SGA LAI choice was significantly associated with BPRS thought disorder (OR = 1.22, CI95% 1.04 to 1.43, p = 0.015) and hostility/suspiciousness (OR = 0.83, CI95% 0.71 to 0.97, p = 0.017) dimensions. The likelihood of receiving an SGA LAI grew steadily with the increase of the BPRS thought disturbance score. Conversely, a preference towards prescribing an FGA was observed with higher scores at the BPRS hostility/suspiciousness subscale. Conclusion Our study is the first to identify predictors of FGA vs SGA choice in patients treated with off-label LAI antipsychotics. Demographic characteristics, i.e. age, sex, and substance/alcohol use co-morbidities did not appear to influence the choice towards FGAs or SGAs. Despite a lack of evidence, clinicians tend to favour FGA over SGA LAIs in bipolar or personality disorder patients with relevant hostility. Further research is needed to evaluate treatment adherence and clinical effectiveness of these prescriptive patterns

The Role of Attitudes Toward Medication and Treatment Adherence in the Clinical Response to LAIs: Findings From the STAR Network Depot Study

Background: Long-acting injectable (LAI) antipsychotics are efficacious in managing psychotic symptoms in people affected by severe mental disorders, such as schizophrenia and bipolar disorder. The present study aimed to investigate whether attitude toward treatment and treatment adherence represent predictors of symptoms changes over time. Methods: The STAR Network \u201cDepot Study\u201d was a naturalistic, multicenter, observational, prospective study that enrolled people initiating a LAI without restrictions on diagnosis, clinical severity or setting. Participants from 32 Italian centers were assessed at three time points: baseline, 6-month, and 12-month follow-up. Psychopathological symptoms, attitude toward medication and treatment adherence were measured using the Brief Psychiatric Rating Scale (BPRS), the Drug Attitude Inventory (DAI-10) and the Kemp's 7-point scale, respectively. Linear mixed-effects models were used to evaluate whether attitude toward medication and treatment adherence independently predicted symptoms changes over time. Analyses were conducted on the overall sample and then stratified according to the baseline severity (BPRS < 41 or BPRS 65 41). Results: We included 461 participants of which 276 were males. The majority of participants had received a primary diagnosis of a schizophrenia spectrum disorder (71.80%) and initiated a treatment with a second-generation LAI (69.63%). BPRS, DAI-10, and Kemp's scale scores improved over time. Six linear regressions\u2014conducted considering the outcome and predictors at baseline, 6-month, and 12-month follow-up independently\u2014showed that both DAI-10 and Kemp's scale negatively associated with BPRS scores at the three considered time points. Linear mixed-effects models conducted on the overall sample did not show any significant association between attitude toward medication or treatment adherence and changes in psychiatric symptoms over time. However, after stratification according to baseline severity, we found that both DAI-10 and Kemp's scale negatively predicted changes in BPRS scores at 12-month follow-up regardless of baseline severity. The association at 6-month follow-up was confirmed only in the group with moderate or severe symptoms at baseline. Conclusion: Our findings corroborate the importance of improving the quality of relationship between clinicians and patients. Shared decision making and thorough discussions about benefits and side effects may improve the outcome in patients with severe mental disorders

Colorectal Cancer Stage at Diagnosis Before vs During the COVID-19 Pandemic in Italy

IMPORTANCE Delays in screening programs and the reluctance of patients to seek medical attention because of the outbreak of SARS-CoV-2 could be associated with the risk of more advanced colorectal cancers at diagnosis. OBJECTIVE To evaluate whether the SARS-CoV-2 pandemic was associated with more advanced oncologic stage and change in clinical presentation for patients with colorectal cancer. DESIGN, SETTING, AND PARTICIPANTS This retrospective, multicenter cohort study included all 17 938 adult patients who underwent surgery for colorectal cancer from March 1, 2020, to December 31, 2021 (pandemic period), and from January 1, 2018, to February 29, 2020 (prepandemic period), in 81 participating centers in Italy, including tertiary centers and community hospitals. Follow-up was 30 days from surgery. EXPOSURES Any type of surgical procedure for colorectal cancer, including explorative surgery, palliative procedures, and atypical or segmental resections. MAIN OUTCOMES AND MEASURES The primary outcome was advanced stage of colorectal cancer at diagnosis. Secondary outcomes were distant metastasis, T4 stage, aggressive biology (defined as cancer with at least 1 of the following characteristics: signet ring cells, mucinous tumor, budding, lymphovascular invasion, perineural invasion, and lymphangitis), stenotic lesion, emergency surgery, and palliative surgery. The independent association between the pandemic period and the outcomes was assessed using multivariate random-effects logistic regression, with hospital as the cluster variable. RESULTS A total of 17 938 patients (10 007 men [55.8%]; mean [SD] age, 70.6 [12.2] years) underwent surgery for colorectal cancer: 7796 (43.5%) during the pandemic period and 10 142 (56.5%) during the prepandemic period. Logistic regression indicated that the pandemic period was significantly associated with an increased rate of advanced-stage colorectal cancer (odds ratio [OR], 1.07; 95%CI, 1.01-1.13; P = .03), aggressive biology (OR, 1.32; 95%CI, 1.15-1.53; P < .001), and stenotic lesions (OR, 1.15; 95%CI, 1.01-1.31; P = .03). CONCLUSIONS AND RELEVANCE This cohort study suggests a significant association between the SARS-CoV-2 pandemic and the risk of a more advanced oncologic stage at diagnosis among patients undergoing surgery for colorectal cancer and might indicate a potential reduction of survival for these patients

ARIA digital anamorphosis : Digital transformation of health and care in airway diseases from research to practice

Digital anamorphosis is used to define a distorted image of health and care that may be viewed correctly using digital tools and strategies. MASK digital anamorphosis represents the process used by MASK to develop the digital transformation of health and care in rhinitis. It strengthens the ARIA change management strategy in the prevention and management of airway disease. The MASK strategy is based on validated digital tools. Using the MASK digital tool and the CARAT online enhanced clinical framework, solutions for practical steps of digital enhancement of care are proposed.Peer reviewe

Search for dark matter produced in association with bottom or top quarks in √s = 13 TeV pp collisions with the ATLAS detector

A search for weakly interacting massive particle dark matter produced in association with bottom or top quarks is presented. Final states containing third-generation quarks and miss- ing transverse momentum are considered. The analysis uses 36.1 fb−1 of proton–proton collision data recorded by the ATLAS experiment at √s = 13 TeV in 2015 and 2016. No significant excess of events above the estimated backgrounds is observed. The results are in- terpreted in the framework of simplified models of spin-0 dark-matter mediators. For colour- neutral spin-0 mediators produced in association with top quarks and decaying into a pair of dark-matter particles, mediator masses below 50 GeV are excluded assuming a dark-matter candidate mass of 1 GeV and unitary couplings. For scalar and pseudoscalar mediators produced in association with bottom quarks, the search sets limits on the production cross- section of 300 times the predicted rate for mediators with masses between 10 and 50 GeV and assuming a dark-matter mass of 1 GeV and unitary coupling. Constraints on colour- charged scalar simplified models are also presented. Assuming a dark-matter particle mass of 35 GeV, mediator particles with mass below 1.1 TeV are excluded for couplings yielding a dark-matter relic density consistent with measurements

Adherence to treatment in allergic rhinitis using mobile technology. The MASK Study

Background: Mobile technology may help to better understand the adherence to treatment. MASK-rhinitis (Mobile Airways Sentinel NetworK for allergic rhinitis) is a patient-centred ICT system. A mobile phone app (the Allergy Diary) central to MASK is available in 22 countries. Objectives: To assess the adherence to treatment in allergic rhinitis patients using the Allergy Diary App. Methods: An observational cross-sectional study was carried out on all users who filled in the Allergy Diary from 1 January 2016 to 1 August 2017. Secondary adherence was assessed by using the modified Medication Possession Ratio (MPR) and the Proportion of days covered (PDC) approach. Results: A total of 12143 users were registered. A total of 6949 users reported at least one VAS data recording. Among them, 1887 users reported >= 7 VAS data. About 1195 subjects were included in the analysis of adherence. One hundred and thirty-six (11.28%) users were adherent (MPR >= 70% and PDC = 70% and PDC = 1.50) and 176 (14.60%) were switchers. On the other hand, 832 (69.05%) users were non-adherent to medications (MPR Conclusion and clinical relevance: Adherence to treatment is low. The relative efficacy of continuous vs on-demand treatment for allergic rhinitis symptoms is still a matter of debate. This study shows an approach for measuring retrospective adherence based on a mobile app. This also represents a novel approach for analysing medication-taking behaviour in a real-world setting.Peer reviewe