Asymmetric Modulation Research Articles

Research on Efficient Single-Sided Asymmetric Modulation Strategy for Dual Active Bridge Converters in Wide Voltage Range

For the problem of narrow soft-switching range and low efficiency of dual active bridge (DAB) converter in wide voltage range, this article proposes a single-sided asymmetric duty modulation (SSADM) strategy, which contains only two control degrees of freedom, and significantly improves the soft-switching performance and efficiency at light load. First, the potential advantages of asymmetric duty modulation (ADM) method are described through waveforms. The principle of determining which full bridge to adopt the ADM is given and the working principle of SSADM is described. Second, a linear pulse logic combination analysis of SSADM in time domain is performed to establish a complete steady-state mathematical model. To solve the analytical expression for the optimal solution of SSADM, the peak-to-peak value of the inductor current with simple expression is chosen as the optimization objective, and the global optimal solution of SSADM is solved based on the Karush–Kuhn–Tucker (KKT) condition, and the voltage closed-loop control strategy of SSADM is presented. In addition, the soft-switching range of SSADM is analyzed. Finally, the experimental platform of DAB converter based on SiC device is built. Compared with other modulation strategies, SSADM shows better soft-switching performance with significant efficiency improvement, which is verified by the experimental results.

An Asymmetrical DAB Converter Modulation and Control Systems to Extend the ZVS Range and Improve Efficiency

This article presents a new optimized hybrid modulation and control systems based on symmetrical and asymmetrical operations of a dual-active-bridge converter to minimize the transformer root-mean-square (RMS) current and extend the zero-voltage-switching (ZVS) range. Various modulation modes are analyzed, and their corresponding power, RMS current equations, and soft-switching conditions are derived. The RMS equations are minimized using the multivariable optimization method, and the corresponding parametric equations are obtained. A hybrid control system has been proposed to regulate the battery current, to ensure smooth inductor current transients, and eliminate the need for a blocking capacitor on the low-voltage side. Using asymmetrical-extended-phase-shift and conventional symmetrical modes, a wider ZVS range is achieved compared to advanced modulations, such as triple phase shift. Moreover, in the low-power region, an optimized RMS current is achieved by applying an optimum dc voltage on the blocking capacitor at the HV side. Hybrid modulation that extended ZVS range and improved RMS current makes the proposed approach a suitable modulation for high-frequency applications and also high-voltage or high-current applications with high <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$C_{\text{oss}}$</tex-math></inline-formula> losses. The efficiency, ZVS operation, and control system performance are validated by a 5 kW converter.

Asymmetrical PWM Scheme to Widen the Operating Range of the Three-Phase Series-Capacitor Buck Converter

The three-phase series-capacitor (3P-SC) buck converter is analyzed extensively in this study for high-voltage step-down applications with a wide input voltage range. This structure is attractive due to its high step-down conversion ratio and inherent current balancing. However, the inductor currents of the 3P-SC converter become unbalanced when the duty cycle exceeds 1/3. This results in significant stress and reduces the utilization of switching devices. This article proposes an asymmetrical pulsewidth modulation (PWM) scheme for the 3P-SC converter to overcome the limitations of the conventional PWM scheme. By using the proposed switching scheme, the duty cycle can be increased to one while retaining the high conversion ratio and current balancing functionality. Thereafter, the proposed asymmetrical PWM strategy is generalized for multiphase series-capacitor (nP-SC) converters. Finally, to validate the performance of the proposed PWM strategy, a 1.2-kW prototype 3P-SC converter is fabricated and tested.

Constant-Current and Constant-Voltage Output Using Hybrid Compensated Single-Stage Resonant Converter for Wireless Power Transfer

At present, single-stage wireless power transfer (WPT) resonant converter with boost bridgeless power-factor-correction (PFC) rectifier has not been promoted due to the rising voltage of dc-link and unstable output voltage of the converter. The compensation network with load-independent constant current output (CCO) and constant voltage output (CVO) characteristics cannot be analyzed in this converter due to the above problems. In order to solve these problems, a new asymmetric modulation method and the corresponding compensation network design method for single-stage WPT converter are proposed in this article. The proposed modulation method makes the voltage of dc link and the output voltage of single-stage WPT converter constant. Based on the new modulation method, the design method of the compensation network and the implementation of zero-voltage switching (ZVS) in single-stage WPT converter are proposed and analyzed in this article. Compared with the other WPT converters, the proposed scheme has advantages in efficiency and cost. Finally, the superiorities of the proposed circuit are verified by experiments.

Switchable asymmetric acoustic field modulation via bilayer coding waveguide arrays

In this work, the acoustic coding waveguide array of a bilayer configuration is proposed to realize asymmetric acoustic field modulation. The designed device is composed of two types of meta-atom, Helmholtz resonator, and air cavity, with high transmittance and opposite phase responses, through which the plane wave is shaped into a focusing beam or splitting beam when input from one side but hardly transmitted when input from the other side. More uniquely, the device can be switched from unidirectional to bidirectional transmission relying on the tunable gap between two composing layers, showing potential applications in acoustic communication, isolation, and stealth.

Nonreciprocal Transport in Noncoplanar Magnetic Systems without Spin–Orbit Coupling, Net Scalar Chirality, or Magnetization

We propose a new mechanism of nonlinear nonreciprocal transport in magnetic systems. By considering a noncoplanar magnetic ordering on a bilayer triangular lattice, we clarify that a local scalar chirality degree of freedom is a source of nonreciprocal transport, which does not require any relativistic spin-orbit coupling, net scalar chirality, and net magnetization. We show a close relationship between the asymmetric band modulation and the nonreciprocal transport under the noncoplanar magnetic ordering based on the model-parameter dependences in the real-space picture.

An Asymmetrical Pulsewidth Modulation With Even Harmonics for Bidirectional Inductive Power Transfer Under Light Load Conditions

An Asymmetrical Pulsewidth Modulation With Even Harmonics for Bidirectional Inductive Power Transfer Under Light Load Conditions

Increasing interhemispheric connectivity between human visual motion areas uncovers asymmetric sensitivity to horizontal motion

Our conscious perceptual experience relies on a hierarchical process involving integration of low-level sensory encoding and higher-order sensory selection.1 This hierarchical process may scale at different levels of brain functioning, including integration of information between the hemispheres.2-5 Here, we test this hypothesis for the perception of visual motion stimuli. Across 3 experiments, we manipulated the connectivity between the left and right visual motion complexes (V5/MT+) responsible for horizontal motion perception2,3 by means of transcranial magnetic stimulation (TMS).4,5 We found that enhancing the strength of connections from the left to the right V5/MT+, by inducing spike-timing-dependent plasticity6 in this pathway, increased sensitivity to horizontal motion. These changes were present immediately and lasted at least 90min after intervention. Notably, little perceptual changes were observed when strengthening connections from the right to the left V5/MT+. Furthermore, we found that this asymmetric modulation was mirrored by an asymmetric perceptual bias in the direction of the horizontal motion. Overall, observers were biased toward leftward relative to rightward motion direction. Crucially, following the strengthening of the connections from right to left V5/MT+, this bias could be momentarily reversed. These results suggest that the projections connecting left and right V5/MT+ in the human visual cortex are asymmetrical, subtending a hierarchical role of hemispheric specialization7-10 favoring left-to-right hemisphere processing for integrating local sensory input into coherent global motion perception.

Optimized Programming Scheme Enabling Symmetric Conductance Modulation in HfO₂ Resistive Random-Access Memory (RRAM) for Neuromorphic Systems

The asymmetric conductance modulation of resistance random access memory (RRAM) is one of the crucial obstacles of the application as artificial synapses for online training. In this work, an optimized programming scheme is proposed to overcome the obstacle. In the optimized programming scheme, the RRAM is grounded through the array parasitic capacitor during the depression process. By harnessing the charging effect of parasitic capacitor, the voltage applied on the RRAM-based synapse is self-regulated according to its conductance. Meanwhile, the linearity of depression process can be tuned by adjusting the operation pulse shape to realize symmetric conductance modulation. The proposed programming scheme is verified by experiment and simulation with a 4 kb RRAM array. Finally, the optimized programming characteristics are applied in the simulation of the training of a VGG-like neural network for the classification of CIFAR-10 dataset. The results show that with the linearity of 6, 88.93% training accuracy is achieved, showing 17.3% accuracy improvement without any overhead either in fabrication process or hardware design cost.

A Single-Stage Wireless Power Transfer Converter With Hybrid Compensation Topology in AC Input

Miniaturization and low cost contribute to the development and popularization of wireless power transfer (WPT). Reducing the number of power conversion stages can reduce the volume and cost of the WPT converter, and even make it possible to improve the efficiency. A single-stage WPT converter with constant current (CC) and constant voltage (CV) output and its asymmetric modulation method are proposed in this paper. A direct AC-AC converter is applied to the primary side of the WPT converter to directly convert line-frequency AC to high-frequency AC. The applied direct AC-AC converter that can replace the commonly used multi-stage primary converter reduces the number of circuit devices, thereby reducing the volume and cost of primary converter. The proposed WPT converter can realize zero voltage switching (ZVS) and power factor correction (PFC). In order to achieve CC and CV output, a switchable hybrid compensation topology is applied to the proposed WPT converter. A 720-W experimental prototype was manufactured to verify the rationality of the proposed WPT converter and the correctness of the theoretical analysis.

Nonlinear nonreciprocal transport in antiferromagnets free from spin-orbit coupling

We theoretically propose a realization of a nonlinear nonreciprocal transport in antiferromagnets without relying on the relativistic spin-orbit coupling. Through the symmetry and microscopic model analyses, we show that a local spin scalar chirality to induce an asymmetric band modulation becomes a source of a Drude-type nonlinear transport, while an electric polarization induced by a collinear spin configuration in a triangle unit leads to a Berry-curvature-dipole-type nonlinear transport. We demonstrate that 120$^\circ$ antiferromagnetic ordering on a triangular lattice and a breathing kagome lattice in an external magnetic field are typical examples. Our results open a new direction of designing and engineering functional materials with showing rich parity-violating transport phenomena by spontaneous magnetic phase transitions.

Effect of Time-Dependent Sinusoidal Boundary Temperatures on the Onset Of Ferroconvection in a Porous Medium

&lt;p&gt;The effect of temperature modulation on the onset of Darcy ferroconvection in a horizontal porous layer heated from below is investigated. The analysis is based on the assumption that the amplitude of the temperature modulation is small enough compared with the imposed steady temperature difference. The effect of the oscillating temperature field is treated by a perturbation expansion in powers of the amplitude of the applied field. The effect of magnetic parameters, Vadasz number and temperature modulation in the cases of symmetric, asymmetric and bottom wall modulation, were discussed. The study divulges that subcritical motion exists for symmetric temperature modulation for low frequency. In the case of asymmetric and bottom wall modulation only supercritical motion exists.&lt;/p&gt;

Is the left hemisphere more prone to epilepsy and poor prognosis than the right hemisphere?

Objective: The central nervous system is known to have asymmetric immune system modulation. Thus far, no clinical study has examined asymmetric immune modulation between hemispheres in focal epilepsy patients. We aimed to compare the prognosis of epilepsy patients lateralized to the right hemisphere with epilepsy patients lateralized to the left hemisphere using clinic and demographic data.Method: Ninety-nine patients with focal epilepsy with all seizures originating in only one hemisphere, between the ages of 18–and 86 years were included. We included patients with focal epilepsy whose seizures were lateralized to only one hemisphere. Age, gender, marital status, education, mental retardation, hand dominance, etiology, trauma, central nervous system infection, febrile convulsion, parental relationships, seizure onset age, seizure frequency (per month), systemic disease, and biochemical parameters were recorded. To evaluate lateralization, we used positron emission tomography (PET/CT), long-term video-electroencephalography (EEG), and magnetic resonance imaging (MRI) investigations.Results: Thirty-seven patients (37.4%) patients were right-lateralized, whereas 62 patients (62.6%) were left-lateralized (p = 0.01). Seizures frequency seizures were higher in patients lateralized to the left hemisphere than in the right. (p = 0.001). In patients with epilepsy lateralized to the left hemisphere, epilepsy onset age was lower (p = 0.003), numbers of antiepileptic medicines were higher (p = 0.04), and epilepsy durations and longest seizure-free periods were longer (p = 0.001 and p = 0.04, respectively).Conclusion: We have shown that compared to the right hemisphere, the left hemisphere is far more prone to seizures and has a poorer prognosis.

(G02 Best Presentation Award Winner) Elaboration and Characterization of CMOS Compatible, Pico-Joule Energy Consumption, Electrochemical Synaptic Transistors for Neuromorphic Computing

Non-Von Neumann computing application constituted by artificial synapses based on electrochemical random-access memory (ECRAM) has aroused tremendous attention owing to its capability to perform parallel operations, thus reducing the cost of time and energy spent [1-3]. Existing ECRAM synapses comprise two-terminal memristors and three-terminal synaptic transistors (SynT). While low cost, scalability, and high density are the highlights for memristors, their nonlinear, asymmetric state modulation, high ON current withdrawal, and sneak path in crossbar array integration prevent them from becoming the ideal synaptic elements for artificial neural networks (ANN) [4]. SynT configuration, on the other hand, offers an additional electrolyte-gated control from which ion doping content can be monitored via redox reactions, thus decoupling write-read actions and improving the linearity of programming states [5-6]. Nevertheless, existing SynTs suffer from different integration issues stemming from liquid-based ionic conductors and manually exfoliated channels. Moreover, several kinds of SynTs possess highly conductive channels in the range of µS to mS, significantly scaling up the energy spent for analog states reading. Despite having numerous communications on the performance of different ECRAM, a comprehensive electrochemical view of ion intercalation into the active material, the main root of conductance modulation, is clearly missing.In this work, we present the elaboration procedure of an all-solid-state synaptic transistor composed of nanoscale electrolyte and channel layers. The devices have been elaborated on 8’’ Silicon wafers using microfabrication processes compatible with conventional semiconductor technology and CMOS back end of line (BEoL) integration. (Figure 1a)We demonstrate the excellent synaptic plasticity properties of short-term potentiation (STP) and long-term potentiation (LTP) of our SynT. We performed tests to study the correlation between linearity, asymmetry, and the number of analog states. By averaging the amount of injected ions per write operation, we estimated the energy consumed for switching among adjacent states of this device is 22.5 pJ, yielding area-normalized energy of 4 fJ/µm2. In addition, operating in the range of nS, our SynTs meet the critical criteria of low energy consumption for both write and read operations. Endurance was highlighted by cycling in ambient conditions with 100 states of potentiation and depression for over 1000 cycles with only a slight variation of Gmax/Gmin ratio of 6.2 % (Figure 1b, c). Approximately 95 % accuracy in MNIST pattern recognition test on ANN in the crossbar array configuration has been obtained by simulation with SynTs as synaptic elements reassured SynT is a promising candidate for future neuromorphic computing hardware.To shed light on the properties of intercalation phenomena of Li ions into the TiO2 layer, a further electrochemical study on a cell comprising Ti/TiO2/LiPON/Li corresponding to the SynT gate stack was performed. This understanding will help to elucidate the correlation with conductance modulation characteristics for a synaptic transistor. Multiple tests were carried out, including cyclic voltammetry (CV) with different scan rates, rate capability with Galvanostatic cycling with potential limit (GCPL), and electrochemical impedance spectroscopy (EIS) on different states of charge. A circuit model was introduced to fit the frequency response of the cell, and it explained well the behavior of charging capability at different OCV (Figure 1d).

An Electrolytic Capacitor-Less PV Micro-Inverter Based on CLL Resonant Conversion With a Power Control Scheme Using Resonant Circuit Voltage Control Loops

A power control scheme with maximum power point tracking based on solely voltage feedback control loops is proposed in this paper for a dc/ac isolated high frequency PV micro-inverter. The presented power circuit topology consists of an integrated continuous conduction mode (CCM) boost converter with an asymmetrical pulse-witch modulation (APWM) controlled CLL step-up resonant converter and a half-bridge grid-side inverter. The presented topology is capable of achieving CCM input current and a wide range of zero voltage switching (ZVS) operation for the front-end stage. The proposed power control scheme, as well as the developed maximum power point tracking (MPPT) control technique utilize the resonant circuit’s resonant capacitor voltage and the APWM input voltage of the resonant circuit only to achieve MPPT and to control the active power of the overall system. By doing so, a large electrolytic input filtering capacitor is not needed. This allows small size film capacitors to be used and improves the system lifetime expectancy. The theoretical analysis and the detailed descriptions of the proposed power control scheme for the presented PV micro-inverter are provided. Simulation and hardware results on a 220 W with 120 Vac, 60 Hz output hardware prototype are presented to demonstrate the performance of the proposed PV inverter system.

On-Chip RF Signal Shaping by Coherent Control of Optically Driven Acoustic Wave Interference

Photonic–phononic systems that mix photons and acoustic waves have been actively investigated for the development of next-generation integrated photonics for signal processing. Here, we propose a new method of arbitrary RF signal shaping using active control of optically driven acoustic-wave interference, offering new photonic–phononic–microwave signal processing schemes with MHz linewidths at GHz carrier frequencies. The demonstrated system consists of two suspended optical waveguides and an asymmetric Mach–Zehnder interferometer. The two waveguides generate acoustic waves at a 3.03 GHz carrier frequency with a 3.3 MHz bandwidth, and one of the paths of the asymmetric interferometer experiences phase modulation induced by the acoustic waves. Then, the interferometer converts the phase information to RF signals of complicated shapes using a linear combination of multiple optical envelopes. This RF signal-shaping method will open new applications of optomechanical systems for microwave photonics.

Novel asymmetric space vector pulse width modulation for dead-time processing in three-phase power converters

&lt;p&gt;This research analyzes the asymmetric control strategies in multilevel inverters, including asymmetric techniques in space vector modulation of power converters. Modulation parameters such as reference voltage vector (Vref), switching time, and duty cycle are derived in the three-dimensional spatial vector geometry formulation. Asymmetric space vector pulse width modulation (SVPWM) is unique in specifying modulation parameters, has unequal tetrahedron patterns, accompanied by application examples for the upper and lower sector pairs of a tetrahedron. The combination of the switch in the form of an inclined cylinder produces twelve pairs of asymmetric tetrahedrons where the voltage vector positions are in the other twenty-four tetrahedrons. The calculation shows processing dead-time in switching, which is used for current compensation in three-phase power converters.&lt;/p&gt;

Neural Network Training With Asymmetric Crosspoint Elements.

Analog crossbar arrays comprising programmable non-volatile resistors are under intense investigation for acceleration of deep neural network training. However, the ubiquitous asymmetric conductance modulation of practical resistive devices critically degrades the classification performance of networks trained with conventional algorithms. Here we first describe the fundamental reasons behind this incompatibility. Then, we explain the theoretical underpinnings of a novel fully-parallel training algorithm that is compatible with asymmetric crosspoint elements. By establishing a powerful analogy with classical mechanics, we explain how device asymmetry can be exploited as a useful feature for analog deep learning processors. Instead of conventionally tuning weights in the direction of the error function gradient, network parameters can be programmed to successfully minimize the total energy (Hamiltonian) of the system that incorporates the effects of device asymmetry. Our technique enables immediate realization of analog deep learning accelerators based on readily available device technologies.

Hybrid-Modulation-Based Full-Speed Sensorless Control for Permanent Magnet Synchronous Motors

This article presents a full-speed sensorless control strategy for permanent magnet synchronous motors (PMSMs) based on a hybrid modulation strategy. The motor operating condition is divided into three ranges: low-speed range, transition range, and high-speed range. A novel two-or-three-vector switching (TTVS) method for rotor position demodulation based on an optimized asymmetric pulsewidth modulation (OAPWM) is proposed in the low-speed and transition regions. A Luenberger position observer based on the conventional symmetric space vector pulsewidth modulation is adopted to demodulate the rotor position in the high-speed region. Additionally, a switching strategy of two modulations and two position estimation observers is proposed to achieve a smooth speed and current transition. Compared with the previous work, the benefits of the TTVS method are to extend the modulation index of the OAPWM and to improve the position estimation accuracy. Finally, the feasibility of the proposed full-speed sensorless control is verified in a 500-W PMSM drive.

Asymmetric modulation of Majorana excitation spectra and nonreciprocal thermal transport in the Kitaev spin liquid under a staggered magnetic field

We present the theoretical results for the Majorana band structure and thermal transport properties in the Kitaev honeycomb model under a staggered magnetic field in addition to a uniform one. The Majorana band structure is asymmetrically modulated in momentum space, and the valley degree of freedom is activated and controlled by the magnitudes and directions of the uniform and staggered magnetic fields; as a result, the Majorana excitation is either gapped or gapless, the latter of which in general has Majorana Fermi surfaces, in contrast to the point nodes in the absence of the fields. We show that the asymmetric deformation of the Majorana band induces a nonlinear (nonreciprocal) thermal transport, in addition to the linear one. The field dependence of the linear thermal current is correlated with the magnitude of the Majorana gap, while that of the nonlinear thermal current is associated with the asymmetry of the Majorana excitation spectra. We show the estimates of the thermal currents and discuss that the linear response is experimentally measurable, whereas future improvement is required for the observation of the nonlinear one. We also discuss how the thermal currents are modulated by other additional effects of the magnetic field and contributions from conventional magnons, latter of which are expected in heterostructures to realize an internal staggered magnetic field.