高轻载效率少功率器件的可模块化扩展ZVS高增益变换器

提出一种高轻载效率且少功率器件的可模块化扩展零电压开关高增益Boost变换器。该变换器可以通过增加升压模块数量n,极大地提高变换器的升压能力;具有2个开关管和n+1个二极管,且各功率管承受相同的电压应力,均为[(n+1)U_(in)+U_(o)]/(n+2);输入电感工作在连续导通模式,其余电感工作在双向导通模式,且反向峰值电流之和大于输入电感电流的谷值,从而实现所有功率管的软开关。所提变换器采用柔性开关频率控制策略,即根据输入电压和负载大小适当地调整开关频率,使电感电流脉动量维持在合适的范围内,既确保实现功率管的软开关,又具有较小的通态损耗,因此在整个负载范围内均具有较高的运行效率。以一个扩展模块为例,对所提变换器的工作原理、稳态特性、软开关条件、控制方法进行深入分析,并通过一台250 W的样机实验验证了理论分析的正确性。

Tunable Three-Wavelength Fiber Laser and Transient Switching between Three-Wavelength Soliton and Q-Switched Mode-Locked States

We report a passive mode-locked fiber laser that can realize single-wavelength tuning and multi-wavelength spacing tuning simultaneously.The tuning range is from 1528 nm–1560 nm,and up to three bands of soliton states can be output at the same time.These results are confirmed by a nonlinear Schrodinger equation model based on the split-step Fourier method.In addition,we reveal a way to transform the multi-wavelength soliton state into the Q-switched mode-locked state,which is period doubling.These results will promote the development of optical communication,optical sensing and multi-signal pulse emission.

Review of Three-phase Soft Switching Inverters and Challenges for Motor Drives

For electric vehicles (EVs),it is necessary to improve endurance mileage by improving the efficiency.There exists a trend towards increasing the system voltage and switching frequency,contributing to improve charging speed and power density.However,this trend poses significant challenges for high-voltage and high-frequency motor controllers,which are plagued by increased switching losses and pronounced switching oscillations as consequences of hard switching.The deployment of soft switching technology presents a viable solution to mitigate these issues.This paper reviews the applications of soft switching technologies for three-phase inverters and classifies them based on distinct characteristics.For each type of inverter,the advantages and disadvantages are evaluated.Then,the paper introduces the research progress and control methods of soft switching inverters (SSIs).Moreover,it presents a comparative analysis among the conventional hard switching inverters (HSIs),an active clamping resonant DC link inverter (ACRDCLI) and an auxiliary resonant commuted pole inverter (ARCPI).Finally,the problems and prospects of soft switching technology applied to motor controllers for EVs are put forward.

Chalcogenide Ovonic Threshold Switching Selector

Today’s explosion of data urgently requires memory technologies capable of storing large volumes of data in shorter time frames,a feat unattain-able with Flash or DRAM.Intel Optane,commonly referred to as three-dimensional phase change memory,stands out as one of the most promising candidates.The Optane with cross-point architecture is constructed through layering a storage element and a selector known as the ovonic threshold switch(OTS).The OTS device,which employs chalcogenide film,has thereby gathered increased attention in recent years.In this paper,we begin by providing a brief introduction to the discovery process of the OTS phenomenon.Subsequently,we summarize the key elec-trical parameters of OTS devices and delve into recent explorations of OTS materials,which are categorized as Se-based,Te-based,and S-based material systems.Furthermore,we discuss various models for the OTS switching mechanism,including field-induced nucleation model,as well as several carrier injection models.Additionally,we review the progress and innovations in OTS mechanism research.Finally,we highlight the successful application of OTS devices in three-dimensional high-density memory and offer insights into their promising performance and extensive prospects in emerging applications,such as self-selecting memory and neuromorphic computing.

Resistive switching behavior and mechanism of HfO_(x) films with large on/off ratio by structure design

Different bilayer structures of HfO_(x)/Ti(TiO_(x)) are designed for hafnium-based memory to investigate the switching characteristics. The chemical states in the films and near the interface are characterized by x-ray photoelectron spectroscopy,and the oxygen vacancies are analyzed. Highly improved on/off ratio(~104) and much uniform switching parameters are observed for bilayer structures compared to single layer HfO_(x) sample, which can be attributed to the modulation of oxygen vacancies at the interface and better control of the growth of filaments. Furthermore, the reliability of the prepared samples is investigated. The carrier conduction behaviors of HfO_(x)-based samples can be attributed to the trapping and de-trapping process of oxygen vacancies and a filamentary model is proposed. In addition, the rupture of filaments during the reset process for the bilayer structures occur at the weak points near the interface by the recovery of oxygen vacancies accompanied by the variation of barrier height. The re-formation of fixed filaments due to the residual filaments as lightning rods results in the better switching performance of the bilayer structure.

Wedge-shaped HfO_(2) buffer layer-induced field-free spin-orbit torque switching of HfO_(2)/Pt/Co structure

Field-free spin-orbit torque(SOT)switching of perpendicular magnetization is essential for future spintronic devices.This study demonstrates the field-free switching of perpendicular magnetization in an HfO_(2)/Pt/Co/TaO_(x) structure,which is facilitated by a wedge-shaped HfO_(2)buffer layer.The field-free switching ratio varies with HfO_(2)thickness,reaching optimal performance at 25 nm.This phenomenon is attributed to the lateral anisotropy gradient of the Co layer,which is induced by the wedge-shaped HfO_(2)buffer layer.The thickness gradient of HfO_(2)along the wedge creates a corresponding lateral anisotropy gradient in the Co layer,correlating with the switching ratio.These findings indicate that field-free SOT switching can be achieved through designing buffer layer,offering a novel approach to innovating spin-orbit device.

Pure State Feedback Switching Control Based on the Online Estimated State for Stochastic Open Quantum Systems

For the n-qubit stochastic open quantum systems,based on the Lyapunov stability theorem and LaSalle’s invariant set principle,a pure state switching control based on on-line estimated state feedback(short for OQST-SFC)is proposed to realize the state transition the pure state of the target state including eigenstate and superposition state.The proposed switching control consists of a constant control and a control law designed based on the Lyapunov method,in which the Lyapunov function is the state distance of the system.The constant control is used to drive the system state from an initial state to the convergence domain only containing the target state,and a Lyapunov-based control is used to make the state enter the convergence domain and then continue to converge to the target state.At the same time,the continuous weak measurement of quantum system and the quantum state tomography method based on the on-line alternating direction multiplier(QST-OADM)are used to obtain the system information and estimate the quantum state which is used as the input of the quantum system controller.Then,the pure state feedback switching control method based on the on-line estimated state feedback is realized in an n-qubit stochastic open quantum system.The complete derivation process of n-qubit QST-OADM algorithm is given;Through strict theoretical proof and analysis,the convergence conditions to ensure any initial state of the quantum system to converge the target pure state are given.The proposed control method is applied to a 2-qubit stochastic open quantum system for numerical simulation experiments.Four possible different position cases between the initial estimated state and that of the controlled system are studied and discussed,and the performances of the state transition under the corresponding cases are analyzed.

Single-atom catalysts based on polarization switching of ferroelectric In_(2)Se_(3)for N2 reduction

The polarization switching plays a crucial role in controlling the final products in the catalytic pro-cess.The effect of polarization orientation on nitrogen reduction was investigated by anchoring transition metal atoms to form active centers on ferroelectric material In_(2)Se_(3).During the polariza-tion switching process,the difference in surface electrostatic potential leads to a redistribution of electronic states.This affects the interaction strength between the adsorbed small molecules and the catalyst substrate,thereby altering the reaction barrier.In addition,the surface states must be considered to prevent the adsorption of other small molecules(such as*O,*OH,and*H).Further-more,the V@↓-In_(2)Se_(3)possesses excellent catalytic properties,high electrochemical and thermody-namic stability,which facilitates the catalytic process.Machine learning also helps us further ex-plore the underlying mechanisms.The systematic investigation provides novel insights into the design and application of two-dimensional switchable ferroelectric catalysts for various chemical processes.

Machine-Learning Based Packet Switching Method for Providing Stable High-Quality Video Streaming in Multi-Stream Transmission

Broadcasting gateway equipment generally uses a method of simply switching to a spare input stream when a failure occurs in a main input stream.However,when the transmission environment is unstable,problems such as reduction in the lifespan of equipment due to frequent switching and interruption,delay,and stoppage of services may occur.Therefore,applying a machine learning(ML)method,which is possible to automatically judge and classify network-related service anomaly,and switch multi-input signals without dropping or changing signals by predicting or quickly determining the time of error occurrence for smooth stream switching when there are problems such as transmission errors,is required.In this paper,we propose an intelligent packet switching method based on the ML method of classification,which is one of the supervised learning methods,that presents the risk level of abnormal multi-stream occurring in broadcasting gateway equipment based on data.Furthermore,we subdivide the risk levels obtained from classification techniques into probabilities and then derive vectorized representative values for each attribute value of the collected input data and continuously update them.The obtained reference vector value is used for switching judgment through the cosine similarity value between input data obtained when a dangerous situation occurs.In the broadcasting gateway equipment to which the proposed method is applied,it is possible to perform more stable and smarter switching than before by solving problems of reliability and broadcasting accidents of the equipment and can maintain stable video streaming as well.

基于同步整流控制器的ZVS反激开关电源技术分析

与准谐振电源相比,传统的零电压开关(ZVS)反激电源可进一步降低开关损耗,但其不利之处是线路复杂,成本上升。本次提出的基于同步整流控制器的ZVS控制策略可实现零电压导通,无需额外附加辅助开关和辅助绕组,具有很好的应用前景。在介绍其工作原理的基础上,给出了仿真结果,并分析了其各时间阶段的工作过程。最后,通过实际系统电路的测试验证了该方法可显著降低开关管的损耗,实现较高的工作效率,并具备成本优势。

Improvement of hepatic fibrosis after tenofovir disoproxil fumarate switching to tenofovir alafenamide for three years

BACKGROUND Both tenofovir alafenamide(TAF)and tenofovir disoproxil fumarate(TDF)are the first-line treatments for chronic hepatitis B(CHB).We have showed switching from TDF to TAF for 96 weeks resulted in further alanine aminotransferase(ALT)improvement,but data remain lacking on the long-term benefits of TDF switching to TAF on hepatic fibrosis.AIM To assess the benefits of TDF switching to TAF for 3 years on ALT,aspartate aminotransferase(AST),and hepatic fibrosis improvement in patients with CHB.METHODS A single center retrospective study on 53 patients with CHB who were initially treated with TDF,then switched to TAF to determine dynamic patterns of ALT,AST,AST to platelet ratio index(APRI),fibrosis-4(FIB-4)scores,and shear wave elastography(SWE)reading improvement at switching week 144,and the associated factors.RESULTS The mean age was 55(28-80);45.3%,males;15.1%,clinical cirrhosis;mean baseline ALT,24.8;AST,25.7 U/L;APRI,0.37;and FIB-4,1.66.After 144 weeks TDF switching to TAF,mean ALT and AST were reduced to 19.7 and 21,respectively.From baseline to switching week 144,the rates of ALT and AST<35(male)/25(female)and<30(male)/19(female)were persistently increased;hepatic fibrosis was also improved by APRI<0.5,from 79.2%to 96.2%;FIB-4<1.45,from 52.8%to 58.5%,respectively;mean APRI was reduced to 0.27;FIB-4,to 1.38;and mean SWE reading,from 7.05 to 6.30 kPa after a mean of 109 weeks switching.The renal function was stable and the frequency of patients with glomerular filtration rate>60 mL/min was increased from 86.5%at baseline to 88.2%at switching week 144.CONCLUSION Our data confirmed that switching from TDF to TAF for 3 years results in not only persistent ALT/AST improvement,but also hepatic fibrosis improvement by APRI,FIB-4 scores,as well as SWE reading,the important clinical benefits of long-term hepatitis B virus antiviral treatment with TAF.

Research on Switching Characteristics Based on Optimization Design of SiC MOSFET Drive Circuit

With the increasing emphasis on energy conservation,emission reduction and environmental protection,the application prospect of SiC power devices is becoming more and more broad.In the high frequency application of SiC MOSFET,the change rate of voltage and current in the turn-on and turn-off process increases with the increase of switching frequency.Also,the current and voltage spike oscillation phenomenon is gradually intensified due to the influence of circuit stray parameters.Based on the analysis of SiC MOSFET characteristics,the paper discusses the design requirements and design principles of SiC MOSFET drive circuit.Then,taking the SiC module C2M0080120D of Cree Company as an example,a driver circuit design is realized through the ACPL-355JC optocoupler driver module of Broadcom Company.The circuit not only has the characteristics of fast transmission delay and excellent performance,but also has the functions of overload and short circuit protection.The driving circuit is verified by LTspice simulation software,and the switching characteristics of SiC MOSFET under different working conditions are studied in depth.The experimental results show that the driving circuit can improve the switching time of SiC MOSFET and effectively solve the problem of current and voltage spike oscillation,which lays a foundation for the practical application of SiC MOSFET in the future.

基于励磁电流补偿与混合移相调制的高频DAB变换器全范围ZVS运行策略

随着宽禁带功率半导体器件的广泛使用,更高开关频率的双有源桥(dual active bridge,DAB)变换器带来了更大的开关损耗,对于软开关技术提出更高要求。为了进一步拓展零电压开通(zero-voltage switching,ZVS)范围,文中对ZVS精确模型和传统电感电流全局最优条件方法进行分析,提出一种结合励磁电流运行的移相调制策略,该策略可实现DAB变换器全功率范围内所有开关管的ZVS运行(8-ZVS运行)。在考虑开关管非线性特性和死区时间限制基础上得到更精确的ZVS模型,并推导引入励磁电流的ZVS模型。此外,所提出的控制方案具有无缝模式转换的特点,电感电流的有效值也可以达到准最佳状态。最后,搭建6kW/150kHz的高频DAB变换器样机以验证模型有效性。实验结果表明,该控制算法可以在任意模式和工况下实现8-ZVS运行,从而提升系统在轻载和中载工况下运行效率。

Improvement on Switching Characteristics and Switching Losses of IGBT by ZVS-PWM

Absrtact: The principle of ZVS - PWM inverting circuit is first described by means of inverting welder supply. The contrastive study is made on switching characte -ristics and switching losses of IGBT between ZVS - PWM and hard - switching.

非反向Buck-Boost变换器的三段式ZVS控制策略

目前文献中的四边形控制方法及其改进方案,能实现非反向Buck-Boost变换器各开关管的ZVS,但存在如下问题:需使用多维查找表或外部存储设备而无在线检测实时计算的闭环、较大的通态损耗和多模式切换引起的输出电压波动等。该文针对上述3个问题提出一种三段式变频ZVS控制策略。首先,去除四边形控制中电感电流的环流续流环节,以减小电感电流有效值并提高效率。其次,在不添加任何额外有源或无源器件的条件眄,将整个宽输入电压范围分成3个模式,分析每个模式的特点,以增加控制条件和简化计算过程,同时实现各模式的在线实时恒压闭环和通态损耗最小ZVS而无需使用多维查找表和线性插值,整体控制简单易实现。然后,提出基于三段式ZVS控制的多模式平滑切换控制策略,可保证在模式切换时各开关管占空比跳变前后,闭环输出始终保持稳定。最后,本文给出了各模式区间划分的理论依据,并搭建500 W实验样机验证了所提方案的有效性。

基于ZVS的双向全桥DC-DC变换器最小回流功率双重移相分段控制

双向全桥DC-DC(DAB)变换器在直流微电网作为可再生能源与储能设备的能量传输环节,通过实现零电压开关(ZVS)和最小回流功率,可显著地提升DAB变换器的性能,从而提高直流微电网的稳定性。但同时实现ZVS和最小回流功率控制在理论上是相互制约的。针对这一问题,该文提出一种基于ZVS的最小回流功率双重移相分段控制策略。通过对双重移相下的传输功率进行分段,前段将ZVS作为约束条件,得到基于ZVS条件下的最小回流功率控制策略,后段通过KKT条件法实现在给定传输功率下的最小回流功率控制策略。通过将所提控制策略和传统的双重移相控制对比分析,发现所提控制策略具有更小的回流功率和电流应力,提高了变换器的性能。最后,基于所提控制策略搭建实验样机,验证了控制策略的正确性和有效性。

基于ZVS变频控制的Si/SiC混合ANPC逆变器损耗评估

零电压开通变频控制(variable frequency controlled zero-voltage-switching,VF-ZVS)可在无辅助电路条件下实现零电压开通(zero-voltage-switching,ZVS),进一步提升碳化硅MOSFET逆变器的功率密度。但在三相有源中点钳位逆变器(active-neural-point-converter,ANPC)中,全功率器件ZVS会大幅增加输出电感电流纹波,改变ANPC逆变器的电流续流路径,影响SiC器件损耗分布特征。论文建立电流纹波关于矢量作用时间的分段数学表达式,提出计及电流纹波的SiC器件损耗建模方法,表征VF-ZVS控制下电流纹波对开关管损耗特性的影响规律。进一步,分析VF-ZVS控制下2SiC、4SiC I和4SiC II 3种典型混合ANPC拓扑的新增工作模态特性;利用所提出的损耗模型,评估在不同调制度、全功率等级下上述3种混合拓扑的开关损耗、通态损耗和损耗分布均衡度,并通过6kW SiC实验平台,在不同功率等级下实验验证了SiC器件损耗模型和3种混合拓扑损耗评估结果的正确性。

一种应用于航天器分布式供电系统的ZVS三端口DC-DC变换器

提出一种应用于航天器分布式供电系统的零电压开关(ZVS)三端口DC-DC变换器(TPC)。对于集成双Buck/Boost双有源桥DC-DC变换器型TPC,一次侧开关管的ZVS范围与3个端口的电压及3个端口之间的传输功率有关。为了实现一次侧开关管ZVS范围的扩展,提出在电路拓扑结构中引入基于耦合电感的辅助电路,相较于传统ZVS实现方法,该拓扑可防止蓄电池端口电流波形上的陷波,进而有利于航天器分布式供电系统中蓄电池寿命的延长。此外,磁耦合电感可减少电感数量,不仅起到滤波作用,还为主开关管提供ZVS实现条件。最后,搭建TPC样机进行实验验证,结果验证该拓扑与控制方法的可行性。

基于扩展移相控制的高频DAB变换器ZVS控制方法

双有源桥(Dual Active Bridge,DAB)在需要高效能量双向流动的工作场景有广泛的应用。在高开关频率工作时,变换器开关器件结电容充放电时间无法忽略,导致扩展移相控制下DAB零电压开通(Zero Voltage Switching,ZVS)范围断续。通过分析扩展移相控制下双有源桥DC-DC变换器工作模态,建立高开关频率工况下DAB变换器数学模型,提出一种利用磁化电流扩宽ZVS范围的方法。在此基础上,结合电感电流应力优化算法,提出一种适用于高频工况应用的电流应力优化下的软开关控制策略。采用该控制策略,可以有效减小导通损耗,消除开关损耗,显著提升高开关频率下的变换器效率。搭建400 kHz实验样机,验证控制策略有效性。

Cooperative Target Tracking of Multiple Autonomous Surface Vehicles Under Switching Interaction Topologies

This paper is concerned with the cooperative target tracking of multiple autonomous surface vehicles(ASVs)under switching interaction topologies.For the target to be tracked,only its position can be measured/received by some of the ASVs,and its velocity is unavailable to all the ASVs.A distributed extended state observer taking into consideration switching topologies is designed to integrally estimate unknown target dynamics and neighboring ASVs'dynamics.Accordingly,a novel kinematic controller is designed,which takes full advantage of known information and avoids the approximation of some virtual control vectors.Moreover,a disturbance observer is presented to estimate unknown time-varying environmental disturbance.Furthermore,a distributed dynamic controller is designed to regulate the involved ASVs to cooperatively track the target.It enables each ASV to adjust its forces and moments according to the received information from its neighbors.The effectiveness of the derived results is demonstrated through cooperative target tracking performance analysis for a tracking system composed of five interacting ASVs.