Minimum Switching Research Articles

Minimum Switching Losses Discontinuous PWM Strategy for Bidirectional Single-Phase AC–DC Converter With Active Power Decoupling Circuit

Active power decoupling circuits are used in bidirectional single-phase grid-connected systems to enhance the circuit lifetime by creating an alternative path for the typical dc-side power pulsating ripple. Therefore, this reduces the requirement of smoothing dc capacitors allowing compact designs even with the implementation of long life metalized film technology. However, with the necessary addition of auxiliary components, extra power losses in the added switching devices and passive components will be introduced, which will inevitably reduce the system power conversion efficiency. To relieve this issue, a new discontinuous pulsewidth modulation (PWM) strategy with minimum switching losses is proposed in this article. This method detects the converter current and reference voltages synchronously to determine the optimum clamped duration of each circuit phase-leg. With such a characteristic, the proposed strategy can realize the minimum switching losses at any instant, thus improving the power conversion efficiency and potentially the power density of the converter. The proposed modulation method is described, analyzed, validated, and compared with different PWM methods on a 2-kVA bidirectional single-phase ac–dc converter with active power decoupling circuit.

Highly Efficient Bidirectional Current-Fed Resonant Converter Over a Wide Voltage Gain Range

In this article, we propose a current-fed bidirectional resonant converter that has minimal switching loss over a wide voltage gain range. The proposed bidirectional resonant converter employs a double current-fed structure at the low-voltage side and an active voltage doubler with a bidirectional switch at the high-voltage side.The converter operates as a pulsewidth-modulation (PWM) double current-fed resonant converter in the forward mode and a PWM half-bridge resonant converter in the backward mode. By incorporating a bidirectional switch across center nodes of the active voltage doubler, the converter achieves almost zero-voltage switching at the turn-off instant, thereby, incurring little switching loss at all active switches. The proposed topology exhibits a high conversion ratio with low transformer turns-ratio and a low current ripple at the low-voltage side. The operating principles and theoretical derivations of the converter are discussed in detail. The performance of the proposed bidirectional converter are verified using a prototype that has 48-72-V low voltage, 380-V high voltage, and 1-kW output power.

Characterizing microfluidic approaches for a fast and efficient reagent exchange in single-molecule studies

Single-molecule experiments usually take place in flow cells. This experimental approach is essential for experiments requiring a liquid environment, but is also useful to allow the exchange of reagents before or during measurements. This is crucial in experiments that need to be triggered by ligands or require a sequential addition of proteins. Home-fabricated flow cells using two glass coverslips and a gasket made of paraffin wax are a widespread approach. The volume of the flow cell can be controlled by modifying the dimensions of the channel while the reagents are introduced using a syringe pump. In this system, high flow rates disturb the biological system, whereas lower flow rates lead to the generation of a reagent gradient in the flow cell. For very precise measurements it is thus desirable to have a very fast exchange of reagents with minimal diffusion. We propose the implementation of multistream laminar microfluidic cells with two inlets and one outlet, which achieve a minimum fluid switching time of 0.25 s. We additionally define a phenomenological expression to predict the boundary switching time for a particular flow cell cross section. Finally, we study the potential applicability of the platform to study kinetics at the single molecule level.

Switching function based on hypergraphs with algorithm and python programming

According to Boolean logic, a disjunctive normal form (DNF) is a canonical normal form of a logical formula consisting of a disjunction of conjunctions (it can also be described as an OR of AND’s). For each table an arbitrary T.B.T is given (total binary truth table) Boolean expression can be written as a disjunctive normal form. This paper considers a notation of a T.B.T, introduces a new concept of the hypergraphable Boolean functions and the Boolean functionable hypergraphs with respect to any given T.B.T. This study defines a notation of unitors set on switching functions and proves that every T.B.T corresponds to a minimum Boolean expression via unitors set and presents some conditions on a T.B.T to obtain a minimum irreducible Boolean expression from switching functions. Indeed, we generate a switching function in different way via the concept of hypergraphs in terms of Boolean expression in such a way that it has a minimum irreducible Boolean expression, for every given T.B.T. Finally, an algorithm is presented. Therefore, a Python programming(with complete and original codes) such that for any given T.B.T, introduces a minimum irreducible switching expression.

E K θ multilevel inverter – a minimal switch novel configuration for higher number of output voltage levels

In this study, a new multilevel inverter (MLI) configuration is proposed to generate higher number of levels with minimal control switches. The proposed inverter's nomenclature is EK θ MLI, termed from its stems of shape. Conventional single-phase H-bridge module is modified to design the structure of θ MLI called ‘θ cell’ (where, K = 0) by incorporating three symmetrical DC-sources and replacing one leg of H-bridge by bidirectional switches. The θ cell of the proposed EK θ MLI generates five-level AC waveform at the output by using only four controlled switches (two unidirectional and two bidirectional). Therefore, the size, cost and switching logic of the MLI is reduced. The basic structure of EK θ MLI called ‘Eθ MLI’ (where K = 1) is designed which is capable of generating seven-level. For further extension, double-switch-E cell (DS-E cell) is added in the middle and each DS-E cell increases the four levels by utilising two bidirectional switches and two DC supplies. The generalised MLI configuration is explained in niceties to generate a higher number of levels (more than 5). The modes of operation, voltage across the switches, power losses of EK θ are discussed. The proposed MLI is experimentally investigated using level shifting pulse width modulation.

Wide voltage gain range application for full‐bridge LLC resonant converter with narrow switching frequency range

In wide voltage range applications, traditional LLC converters suffer from the following issues: (i) to cover a wide voltage gain operating range, the required switching frequency range is also large, which challenges the design and optimisation of magnetic components, gate driver circuitry, and electro-magnetic interference filter; (ii) a small magnetising inductance is preferred in wide voltage gain range application, which leads to the increase of circuit circulating current and corresponding conduction loss; (iii) passive elements are determined based on the minimum switching frequency, so bulky passive elements are required to satisfy the required operation range. To solve these problems, in this study, a full-bridge LLC (FBLLC) resonant converter with two operation modes, namely full-bridge operation and frequency doubler operation, is proposed for wide voltage gain range application. The FBLLC converter discussed in this study can be designed in half of the input voltage range when compared with the conventional method, so smaller switching frequency operating range and higher efficiency operation are guaranteed. In addition, the smooth mode transition is achieved by introducing switching frequency feedforward control and small output voltage overshoot or undershoot is observed. A 150 W experimental prototype was built to validate the theoretical analysis.

A Nonisolated High Step-Up Three-Port Soft-Switched Converter With Minimum Switches

In this article, a nonisolated high step-up three-port converter is proposed based on the single-ended primary-inductor converter. The proposed converter includes two switches, which are turned <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</small> under zero voltage switching or low-voltage condition intrinsically. The overall number of elements used in the converter is small. Furthermore, the conduction losses are reduced by reducing the number of the semiconductor elements in both battery and photovoltaic (PV) current flow paths. The input inductor is not coupled to any inductors to reduce the PV current ripple and enhance the realization of maximum power point tracking (MPPT). Since low-voltage switches with low <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</small> -resistance are selectable, conduction losses are reduced. All modes of operation in the steady-state condition are discussed and design considerations in each mode are presented. Finally, the experimental prototype of the proposed converter with a 24 V PV source, 36 V battery pack, and a 380 V-200 W load is presented.

High voltage DC power supply with power factor correction based on LLC resonant converter.

This paper presents analysis, design and experimentation of a high voltage DC power supply (HVDCPS) with power factor correction based on LLC resonant converter. For power factor correction improvement, the proposed topology has an input rectifier with two filter capacitors, two inductors with a bus capacitor (Cbus) and a resonant tank. To prevent the reverse current flow towards the source diodes (D9 & D10) are employed. A couple of power switches are inserted in a single leg that makes a half-bridge network. To form an LLC resonance circuit, a capacitor and two inductors are connected to the primary winding of the high voltage transformer (HVT). To rectify the high frequency and high voltage, a full-bridge rectifier is inserted to secondary side of high voltage transformer (HVT). The secondary diodes always get on and off under zero current switching (ZCS) due to discontinuous conduction mode of proposed topology. It is found that due to power factor correction, less cost, lower losses and smaller size, the proposed topology achieves several major improvements over the conventional high voltage power supply. To obtain zero voltage switching (ZVS) the converter operate in a narrow frequency range. The output voltage can be varied or regulate through pulse width modulation of power switches. Due to ZVS and ZCS, the proposed topology has minimum switching losses and therefore higher efficiency. To verify the feasibility of the proposed topology a prototype is being implemented and verified by simulation & experimental results for 1.5KV prototype of the proposed topology. The results make sure the achievement, good efficiency and successful operation of the proposed topology.

Optimally Tuned Interleaved Luo Converter for PV Array Fed BLDC Motor Driven Centrifugal Pumps Using Whale Optimization Algorithm—A Resilient Solution for Powering Agricultural Loads

The use of brushless direct current (BLDC) motors are gaining much prominence in water pumping systems (WPS), especially for agricultural purposes. In most cases, the BLDC based WPS is powered using electricity from the grid, which is vulnerable to disruptive events causing a resilience problem. However, to avoid the resilience issue, grid-interactive solar photovoltaics (PV) are being used, and this is due to the increased penetration of distributed generation sources into the grid. In these systems, based on the inherent nature of solar PV, power converters are preferred, and as a result, problems like switching losses and maintaining steady-state voltages are commonly seen. In this paper, a framework of PV powered WPS with scope for optimizing controller parameters is proposed to avoid the above-raised issues. Based on the proposed framework, the overall structure of the PV powered WPS is modeled, designed, and analyzed. In the proposed system, the power output from solar PV is fed to the BLDC motor and the grid. If any problem arises in obtaining the power from solar PV, grid-interaction helps to run the motor at required speeds making the WPS resilient to unexpected disruptions and vice versa. For retrieving the generated power from PV array, a positive interleaved Luo converter (I-Luo) is used, which boosts the output with minimum switching losses. To maintain the steady-state voltage at the output of the I-Luo converter, a proportional-integral (PI) controller whose parameters are tuned by whale optimization algorithm (WOA) is used. This voltage is fetched to the BLDC motor via a 3-phase (3-Ф) inverter and then to the grid via a single-phase (1-Ф) inverter. The overall system is simulated and experimentally validated, with a detailed analysis of the observed results. The results include the various performance characteristics of the solar PV, converter, and BLDC motor. Besides, by using the field-programmable gate array (FPGA) based SPARTAN6E controller, the performance of the I-Luo is examined experimentally.

Interplay between stacking order and in-plane strain on the electrical properties of bilayer antimonene

In this work, the electrical properties of bilayer Antimonene with different stacking orders are studied. Density functional theory with van der Waals (vdW) correction is used to investigate the electrical performances. Two configurations demonstrate considerable bandgaps, whereas, the bandgaps are close to zero for other structures. The in-plane biaxial strain is applied to modify the electrical properties. The bandgap reaches a maximum at a specific strain level and then closes at more enormous compressive and tensile strains . The energy of three valleys (Γ, Q, and K) in the conduction band are explored with the strain. The conduction band minimum switches between these valleys with the strain. Two bands also contribute to the valence band maximum, and the energy of these two bands for various strains is investigated. Finally, the effective mass for the valleys of the conduction band and the valence band are obtained. The effective mass at Γ-valley demonstrates the lowest effective mass. • The electrical and structural properties of five different stacking orders of bilayer antimonene are studied using DFT. • Two configurations AA2 and AB2 demonstrate considerable band gaps of 0.57 and 0.58 eV, respectively. Three other structures display a low band gap of around 0.1 eV. • The maximum values of the band gaps in the presence of strain are 0.778 eV and 0.774 eV for structures AA2 and AB2, respectively. • The CBM switches between three valleys (Γ, Q and K) under different strains. On the other hand, two bands contribute to the VBM at Γ-point. • The effective mass for Γ-valley displays the lowest effective mass for all range of strain.

Fast, Highly Flexible, and Transparent TaOx-Based Environmentally Robust Memristors for Wearable and Aerospace Applications

Memristor devices that can operate at high speed with high density and nonvolatile capabilities have great potential for the development of high data storage and robust wearable devices. However, in real-time, the performance of memristors is challenged by their instability toward harsh working conditions such as high temperature, extreme humidity, photo irradiation, and mechanical bending. Herein, we introduce a TaOx/AlN-based flexible and transparent memristor device having stable endurance under extreme 2 mm bending (for more than 107 cycles) with an ON/OFF ratio of more than 2 orders of magnitude at 25 ns rapid switching. This device exhibits excellent flexibility under extreme bending conditions (bending radius of 2 mm) even with intense ultraviolet (UV) radiation. A thin AlN insertion layer having low dielectric and high thermal conductivity plays a crucial role in improving the switching stability and device flexibility. In particular, the devices exhibit excellent minimum switching fluctuations under UV irradiation, >106 s nonvolatility retention at high temperature (135 °C), various gas ambient, and damp heat test (humidity 95.5%, 83 °C) because of the indium metal drift during the switching process and high bonding energy of Ta–O. Most importantly, direct observation of indium metal strongly anchored in the TaOx switching layer during the switching process is reported for the first time via transmission electron microscopy, which provides clear insights into the switching phenomenon. Furthermore, the results of electrical and material analyses explain that our facile device design has excellent potential for wearable and aerospace applications.

Non‐isolated LLC resonant converter with suppressed circulating current and automatic resonant frequency matching capability

This study proposed a novel non-isolated half-bridge Inductor-Inductor-Capacitor (HB LLC) resonant converter with automatic resonant frequency adjustment ability and a circulating current suppression auxiliary circuit. The proposed converter employs a hybrid modulation technique based on frequency modulation (FM) and pulse width modulation (PWM) to regulate the output voltage. At the nominal operating point, all the excellent attributes of a conventional LLC converter over the entire load range are maintained and output voltage control is achieved with FM. However, when the input voltage decreased to a level that LLC output voltage cannot be maintained with FM, the primary switches will operate at the minimum switching frequency and the auxiliary switch will be turned ON with PWM. The auxiliary switch is turned ON with zero-voltage switching and automatically matching the circuit resonant frequency with the switching frequency for optimal operation. The effective resonant inductor is energised directly from the dc bus storing more energy which is later released to the load to achieving high gain while maintaining the desired output voltage with a narrow frequency span. In addition, the converter exhibits low circulating current under an enhanced gain condition. Experimental results are presented on a 60 W prototype to validate the theoretical prediction. The proposed converter has a peak efficiency of 97%.

Analysis and Design of a New Current-Source Output Load Resonant Converter With High Capability in Line and Load Regulation

In this paper a fourth-order Passive Resonant Tank (PRT) is introduced using a topological modification in LLC tank for current-source output applications of Load Resonant Converters (LRCs). The design procedure is based on the output current/input voltage ratio decoupling from the load coefficient. Therefore, output current can be independent of load variation topologically. In this condition, new criterions are applied on the operational frequency and PRT components ratio. Moreover, kVA/kW ratio of the LRC is considered as a comparing index, to optimize the converter size as well as reduction of voltage/current stresses on the PRT components. To reduce the discrete components number, transformer parasitic inductances and bridge capacitors are used as the PRT components. Also, a simple and accurate PWM-based Quasi-Proportional Controller (QPC) is designed to maintain the output current constant against input voltage variations. Minimum reactive power, low circulating and turn-off current, and ZVS of the inverter switches in a wide loads range are obtained as the advantages of the designed LLCC-LRC. Moreover, sinusoidal shape of the PRT input current and minimum switching losses on the rectifier are maintained. Finally, an experimental prototype with 3.5A output current and 93.9% efficiency is presented for results verification.

Open-Current Vector Based SVM Strategy of Sparse Matrix Converter for Common-Mode Voltage Reduction

The concept of open-current vector for sparse matrix converter is put forward along with its application constraints in this article. Based on the open-current vector, an improved space vector modulation (SVM) strategy is proposed to reduce the peak magnitude of common-mode voltage (CMV) by 42.3% without sacrificing the performance of input and output waveforms and the voltage transfer ratio (VTR). First, the application constraints and common-mode equivalent circuit of the open-current vector in the rectifier stage of the sparse matrix converter are analyzed. After that, in accordance with the principle of minimum switching action and two adjacent active vector synthesis, the improved SVM strategy used a suitable open-current vector instead of the active-current vector in the rectifier stage when the zero-voltage vector is used in the inverter stage, which contributes to CMV reduction. The improved SVM strategy not only reduces the peak magnitude of the CMV, but also ensures that the performance of input and output waveforms and the VTR are the same with those of traditional SVM. Finally, the effectiveness of the improved SVM strategy is verified by simulation and experiments.

Modified DPWM Method for Vienna Rectifier Considering Current Harmonic Distortions Reduction and Neutral Point Potential Balance

A Vienna rectifier has been widely applied when power density is a design objective and usually works with a high switching frequency. Therefore, it is necessary to decrease the switching loss to reduce the temperature of the device. Discontinuous pulse width modulation (DPWM) is able to reduce the switching loss of power of the device. However, the five‐stage vector synthesis method of DPWM will increase the current harmonics. To reduce the current harmonic distortions caused by the DPWM method and reduce the switching loss of a Vienna rectifier, a modified DPWM modulation method with minimum switching loss for a Vienna rectifier is proposed in this paper, and the reduction of current harmonic is achieved by injecting the optimal zero‐sequence component into three‐phase modulation waves in the subsectors at the large‐sector transitional area. Furthermore, the three‐level topology has a problem of unbalanced neutral point potential. By changing the clamp mode in each subsector leading to different currents, leading to the neutral point, the neutral point potential is balanced. Finally, all these proposed modulation and control strategies are verified by simulation and experiment results. © 2020 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC.

State Switched Discrete-Time Model and Digital Predictive Voltage Programmed Control for Buck Converters

Switched mode power converters are nonlinear systems, and it is a constant challenge to improve their modeling accuracy and control performance. In this paper, a State Switched Discrete-time Model (SSDM) is proposed, which achieves a higher accuracy at a high frequency than that of conventional state averaged models. Instead of averaging the converter states for approximation, the states within each switching cycle are considered in the modeling. Based on total differential equations of switching-ON and switching-OFF durations, the inductor current and output voltage within a cycle are accurately calculated, which derives the SSDM. Furthermore, a Digital Predictive Voltage Programmed (DPVP) control strategy is derived through the SSDM. Through voltage prediction, a suitable duty ratio is calculated that regulates the output voltage to its reference value in the minimum switching cycles. In this way, the converter achieves a very fast load/line transient response and reference tracking speed, and it exhibits a high stability under deviated inductance. Finally, the accuracy of SSDM and the system stability are proved by frequency response analyses and experiments.

프리프레그 가공을 통한 인쇄회로 기판의 유효 유전상수 하향 조정

As electronic devices become more compact, the thickness of the layer in printed circuit boards(PCBs) decreases, and the characteristic impedance of transmission lines with a minimum allowable trace width often becomes less than 50 Ω. Reducing the minimum trace width or switching to a dielectric with lower dielectric constant is prohibitive owing to increased manufacturing costs. We propose a new way of reducing the effective dielectric constant by drilling holes in prepreg. We perform measurements and simulations to verify the effectiveness of the proposed approach. Results demonstrate that using drilled prepreg enables the lowering of the effective dielectric constant by up to 7 %.

Optimum diameter for laser beam and effect of temperature rise on the optical bistability hysteresis loops

In this research, analytical study for simulating a Fabry-Perot bistable etalon (F-P cavity) filled with a dispersive optimized nonlinear optical material (Kerr type) such as semiconductors Indium Antimonide (InSb). An optimization procedure using reflective (~85%) InSb etalon (~50µm) thick is described. For this etalon with a (50 µm) spot diameter beam, the minimum switching power is (~0.078 mW) and switching time is (~150 ns), leading to a switching energy of (~11.77 pJ) for this device. Also, the main role played by the temperature to change the etalon characteristic from nonlinear to linear dynamics.

A Novel High Voltage Gain SEPIC Converter Based on Hybrid Split-Inductor for Renewable Application

ABSTRACT The modified single-ended primary inductor converter (SEPIC) reported in the literature has limitations namely, low static gain and high input current ripples. This resulted in poor efficiency with high switching losses and switching stress. Hence, in order to overcome the above-said limitations, this paper proposes a high static gain SEPIC converter with reduced input current ripple. The proposed converter resembles a split-inductor design consisting of three diodes and two inductors. The static gain of the converter is significantly improved while input current ripple gets reduced by using a split-inductor. Additionally, the low value of input current ripple causes minimal switching stress and switching losses. Hence, the efficiency of the proposed converter improves significantly. The working principle and theoretical analysis of the proposed converter is studied in detail for continuous, discontinuous and boundary conduction modes. Moreover, a small signal/transient analysis is also discussed to validate the feasibility as well as the stability of the proposed system using the transfer function approach. In order to validate the effectiveness of the proposed converter, a MATLAB/Simulink model has been designed. Further, a laboratory prototype has been developed and the experimental results obtained are in agreement with the simulated results.

Performance enhancement of an ultra-scaled double-gate graphene nanoribbon tunnel field-effect transistor using channel doping engineering: Quantum simulation study

In this paper, new graphene nanoribbon tunnel field-effect transistors (GNRTFETs) endowed with specific doping profiles are proposed, assessed, and compared with the conventional design through a computational investigation. The used quantum simulation is based on solving self-consistently the Poisson and Schrödinger equations using the non-equilibrium Green's function formalism in the ballistic limit. The numerical study deals with GNRTFET designs with 5 nm gate length while comparing their I-V transfer proprieties, subthreshold swing, charge density, current ratio, intrinsic delay, and power-delay product. The proposed designs, which are endowed with new doping profiles, have been found efficient in mitigating the direct source-to-drain tunneling issue of ultrascaled GNR-based TFET and in improving the ambipolar behavior while boosting the performance of the GNRTFETs. As interesting results, highly improved minimum leakage current, subthreshold swing, and switching parameters have been recorded by means of the proposed channel doping engineering-based approach. The obtained substantial improvements in the performance of ultrascaled GNRTFETs make the proposed approach as a promising way for the continual shrinking of tunnel field-effect transistors (sub-5-nm) while maintaining the required high-performance.