Hard-switching Mode Research Articles

An Innovative Design Approach for Resonant DC/AC Converters, Based on Symmetry in Their Operating Modes

The manuscript presents an innovative approach for the engineering design of resonant DC/AC converters used as sources of high-frequency electricity for a variety of needs: industrial and domestic applications, wireless power transmission, high-performance lighting, and more. The methodology is based on the generalized consideration of electromagnetic processes in a series resonant RLC circuit fed by a square-wave voltage source. Due to the symmetry in the form of the current in the AC circuit of the DC/AC converter, it is possible to generalize all their possible operating modes. This was realized by applying the quasi-boundary method to the analysis of resonant DC/AC converters with and without reverse diodes operating in soft and hard switching modes. On this basis, the transfer functions of the devices, which give the relationship between their output and input voltages, are defined and analytically determined. Additionally considered are cases of resonant DC/AC converters with complex output circuits, which are applied to match the load needs and the capabilities of the power electronic device. In this sense, the basic dependencies for designing the main types of resonant DC/AC converters using series and parallel load compensation are given. The effectiveness of the proposed methods is demonstrated through several examples, and their verification and validation is achieved with simulations and prototypes. The proposed innovative design approach is applicable not only in power electronics education, but also in the design and prototyping of a whole class of power electronic devices. The unification of design methodologies formalizes and algorithmizes the design process, which is an important step for its automation and for applying various optimization procedures to achieve certain goals.

An Analytic Model of Electrochemical Metallization Memristor With a Cluster Spontaneous Decay

An important requirement for memristor applications in functional circuits is a predictable analysis model to capture the resistance switching and synaptic behaviors. Although several memristor models based on the electrochemical metallization (ECM) mechanism have been proposed, they do not match the actual memristor with a “memory forgetting” property caused by the spontaneous decay of metal clusters in the conductive channel. Therefore, an analytic model is developed for the memristor based on the ion drift and the cluster decay. The vertical and lateral dynamics of conductive region are described by two internal state variables, i.e., the length and the diameter. It is verified that the model with the decay effect fits well with the actual device by reproducing the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${I}$ </tex-math></inline-formula> – <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${V}$ </tex-math></inline-formula> characteristic and the synaptic function. This model reveals that synaptic weight depends on the interval, amplitude, and duration of applied pulses. The effects of several key parameters on conductive decay and resistance switching are discussed here. The model can work in a hard-switching mode. This article describes some potential applications in electronic schemes using the model.

GaN-Based Multichip Half-Bridge Power Module Integrated on High-Voltage AlN Ceramic Substrate

Power electronic systems employing wide-bandgap GaN transistors promise high efficiency operation and power density but require minimized parasitic circuit elements and an effective cooling concept. This article presents a half-bridge module integrating two 600 V/170 mΩ gallium nitride (GaN) high-electron mobility transistors with their gate drive stages and a fraction of the dc-link capacitance on a patterned multilayer polycrystalline AlN-substrate. The high-voltage isolation at a layer distance of 10 μm and a dense chip-by-chip integration on the GaN half-bridge module enable a compact lateral commutation loop design combined with improved cooling capability of the power transistors. Consequently, the GaN half-bridge module allows for higher load currents at lower device temperature while most parasitic circuit elements are reduced compared to a conventional printed circuit board (PCB) design. The parasitic circuit elements of the GaN half-bridge module and a reference four-layer PCB half-bridge are evaluated using 3D-FEM field simulation and in-circuit measurements. Selected finite element method (FEM) simulation results are validated by <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">S</i> -parameter measurements and further used to parametrize a lumped commutation loop model. The thermal characterization of the GaN half-bridge module validates the improved cooling capability of the GaN half-bridge power module. Transient switching characteristics are studied in hard-switching mode. The device temperature and converter efficiency are evaluated in dc/dc buck-converter operation.

Single Input Single Output Two Level Isolated Dc-Dc Converter With Secondary Side Phase Shifting For Solar Applications

The isolated dc–dc converters with primary-side phase shifting (PPS) provides severely narrow soft-switching range for main devices in the primary side leg of full bridge converter. The leakage inductance of the high frequency transformer should be large enough for providing the energy needed for soft switching operations and also the idling power loss due to circulating current in the converter legs under large phase-shift angle, which makes reduction of conversion efficiency and complicated in designing the parameters of transformer. Furthermore, the turn-off diode commutations in the output-side rectifier are performed by hard-switching mode. To overcome all these drawbacks, a secondary side phase shifting (SPS) technique has been developed for two-level isolated DC-DC converter. This scheme provides wider soft switching range and reduced power loss due to elimination of circulating current in the primary side of high frequency transformer. In addition, SPS control also provide no reverse recovery current in diodes and hence no power losses in the secondary rectifier circuit. The control switches operate under soft switching even under rated load and short circuit conditions.&#x0D;

Characterization of 3.3-kV Reverse-Blocking SiC Modules for Use in Current-Source Zero-Voltage-Switching Converters

Silicon carbide (SiC) MOSFETs with ratings of 3.3 to 15 kV represent a dramatic improvement over available silicon devices, enabling the realization of medium-voltage converters in demanding applications such as solid-state transformers. Typical voltage-source converter configurations realize significant reduction in switching loss with SiC devices, but high dv/dt of 30–50 kV/ μ s generates high levels of electromagnetic interference (EMI) and displacement currents. Current-source based zero-voltage switching (CS-ZVS) converters such as the soft-switching solid-state transformer (S4T), dramatically reduce switching loss using ZVS, thus realizing both controlled dv/dt and low EMI. CS-ZVS converters require reverse blocking (RB) modules that are realized using series connection of a diode and a MOSFET. However, no data are available from manufacturers or from literature on RB module characterization under ZVS conditions. This article presents detailed characterization results and model extraction for a 3.3 kV 45 A and a 1.7 kV 10 A SiC RB module, under both hard switching and ZVS modes. A novel double-pulse testbed is designed and built for this characterization of RB devices under both hard switching and ZVS conditions. Significantly, it is shown that when the RB modules are used in CS-ZVS converters, the dynamic voltage sharing between the RB modules in a phase leg and within the RB module (between the diode and the switch) results in a unique voltage stress. Modulation strategies to address this unique voltage stress are proposed and verified through experiment results, using a S4T prototype rated at 1.5 kV, 10 kVA .

Hard-Switching 650-V GaN HEMTs in an 800-V DC-Grid System With No-Diode-Clamping Active-Balancing Three-Level Topology

For any voltage above 600-V dc, it is usually recommended to use 900–1200-V SiC MOSFETs instead of GaN high-electron-mobility transistors (HEMTs), given presently commercial GaN HEMTs have the maximum voltage rating up to 650 V. This paper is an attempt of employing 650-V E-mode GaN HEMTs to build a three-level bidirectional dc/dc converter, with the input as an 800-V battery, the output as the ~400-V dc grid, and half of the switches working at the hard-switching mode. The active-balancing control instead of using clamping diodes in the conventional neutral-point clamping topology is adopted, aiming at higher efficiency. Simulation based on the double-pulse test results shows that such a design strategy with GaN has a better efficiency over the conventional 1200-V SiC MOSFET-based buck/boost converter. Two bottom-cooled GaN HEMTs are in parallel to enhance the power capability and efficiency, which require the special focus on the parasitic parameters. The effects of parasitics, especially the stray inductance in the current commutating loop and the gate drive loop during switching transitions, have been comprehensively analyzed in this paper. Experimental results under 800-V bus voltage are presented to verify the proposed solution.

Analysis and Simulations of Hybrid Memory Scheme Based on Memristors

The investigation of new memory schemes is significant for future generations of electronic devices. The purpose of this research is to present a detailed analysis of the processes in the memory elements of a memory section with memristors and isolating Metal Oxide Semiconductor (MOS) transistors. For the present analysis, a modified window function previously proposed by the author in another memristor model is used. The applied model is based on physical nonlinear current-voltage and state-voltage characteristics. It is suitable for illustration of the processes in the memristors for both writing and reading procedures. The memory scheme is simulated using a nonlinear drift model with an improved window function. The used model was previously adjusted according to the reference Pickett model. The memory circuit is analyzed for writing and reading information procedures. The memristor current-voltage relationship is compared to physical experimental characteristics and to results acquired by the use of basic window functions. A satisfactory coincidence between the corresponding results is established. For the used logical signals, the memory elements operate in a state near to hard-switching mode. It is confirmed that the memristor model with a modified window function applied here is suitable for investigating complex memristor circuits for a general operating mode.

Efficient solution of the DC-link hard switching inverter of the PV system

Soft switching inverter alleviate and treat the negative impacts resulted from hard switching inverter. It provides many advantages such as low power losses, high efficiency, stress reduction during switching instants, and high reliability and lowering EMI generation. Soft switching is achieved in this paper by adding the LC resonant circuit to the voltage source inverters (VSI). This is the first time to achieve soft switching with the photovoltaic (PV) system. To demonstrate the effectiveness of this technique, the simulation of the PV system is using both switching techniques; the resonant dc-link soft switching inverter and the conventional hard switching inverter; is introduced, analyzed and compared. The total resonant dc-link soft switching losses are reduced dramatically to the half of the total hard switching losses in case of not using soft switching. To validate our work, the detailed comparisons between the proposed topology with another famous one is introduced, analyzed and evaluated. In addition, the resonant dc-link soft switching losses and the hard switching losses of the inverter are estimated. The total resonant dc-link soft switching losses and the total hard switching losses are calculated under similar operating conditions and the conduction losses are kept constant in both switching modes. The simulation results prove the superiority performance of the PV system based on the proposed resonant dc-link soft switching mode compared to the other ones based on the conventional hard switching mode and single transistor resonant dc-link soft switching inverter.

ANALYSIS OF AN ANTI-PARALLEL MEMRISTOR CIRCUIT

The basic purpose of the present paper is to propose an extended investigation and computer analysis of an anti-parallel memristor circuit with two equivalent memristor elements with different initial values of the state variables using a modified Boundary Condition Memristor (BCM) Model and the finite differences method. The memristor circuit is investigated for sinusoidal supply current at different magnitudes – for soft-switching and hard-switching modes, respectively. The influence of the initial values of the state variables on the circuit’s behaviour is presented as well. The equivalent i-v and memristance-flux and the other important relationshipsof the memristor circuit are also analyzed.

ADVANCED MEMRISTOR MODEL WITH A MODIFIED BIOLEK WINDOW AND A VOLTAGE-DEPENDENT VARIABLE EXPONENT

The main idea of the present research is to propose a new nonlinear ionic drift memristor model suitable for computer simulations of memristor elements for different voltages. For this purpose, a modified Biolek window function with a voltage-dependent exponent is applied. The proposed modified memristor model is based on Biolek model and due to this and to the use of a voltage-dependent positive integer exponent in the modified Biolek window function it has a new improved property - changing the model nonlinearity extent dependent on the integer exponent in accordance with the memristor voltage. Several computer simulations were made for soft-switching and hard-switching modes and also for pseudo-sinusoidal alternating voltage with an exponentially increasing amplitude and the respective basic important time diagrams, state-flux and i-v relationships are established.

A 98.3% Efficient GaN Isolated Bidirectional DC–DC Converter for DC Microgrid Energy Storage System Applications

This paper presents a novel 400 to 12 V isolated bidirectional dc–dc converter based on a phase-shift-controlled-modified dual-active-bridge power stage. The proposed converter consists of a half-bridge and center tap with active clamp circuit, which has promising performance for low-voltage high-current applications. 650 V gallium-nitride high electron mobility transistors are used on the high voltage side to avoid issues encountered using Si superjunction MOSFETs in phase-shift-controlled-bidirectional power conversions. The operation principle and power transfer characteristic are obtained based on a time-domain analysis of the inductor current. Design methodology and criteria and converter's efficiency analysis are discussed. Both the analysis and experiments verify that the proposed converter is capable of achieving low power loss and high power density in soft-switching and hard-switching modes. Experimental results are presented for a 1-kW, 400 V-to-12 V dc–dc prototype converter operating at 100 kHz switching frequency. A power density of 30 W/in3 and a peak efficiency of 98.3% in a wide input/output voltage range are achieved.

Harmonic Spectra Shaping for Switched Reluctance Motor with Asymmetric-Carrier Random PWM

To alleviate the undesirable vibration and acoustic noise of switched reluctance motor (SRM), an asymmetric-carrier random PWM (ACRPWM) method is designed to shape the harmonic spectra for the speed control of the SRM. The ACRPWM can not only effectively spread the harmonic spectra of the voltage to a more wide frequency range, but also maintain the fixed switching frequency in the control of the converter. The shaping of the harmonic spectra can reduce the harmonic components beside the switching frequency and its integer multiples. The harmonic spread factor and total harmonic distortion are used to evaluate the performance of the ACRPWM. The ACRPWM is tested on hard and soft switching modes of the converter in the speed control of the SRM, respectively. Simulation results certify the effectiveness of the proposed ACRPWM in the shaping of the harmonic spectra for the SRM.

A Wide-Input-Range Efficiency-Enhanced Synchronous Integrated LED Driver With Adaptive Resonant Timing Control

A wide-input-range DC–DC-based dimmable LED driver is presented in this paper. The proposed LED driver can be automatically configured to operate in the soft-switching mode under the high-voltage condition in order to minimize the converter’s dominant switching power loss. Adaptive resonant timing control is developed to enable proper dead-time generation for on-chip high-voltage power FETs in both hard- and soft-switching modes under different input and output voltages for the power loss minimization. In the proposed LED driver, two low-power body-diode-based zero-voltage detectors and an adaptive resonant timing emulator are also proposed for providing accurate and high-speed zero-voltage switching (ZVS) detection of both power FETs, and achieving optimal quasi-ZVS condition, respectively. Implemented in a 0.5 $\mu \text {m}$ HV CMOS process, the proposed buck-based LED driver can support an input voltage range from 5 V to 115 V and up to 25 series-connected high-brightness LEDs with the maximum output power of 25 W. The LED driver can operate up to 1.6 MHz in the soft-switching mode and 2.2 MHz in the hard-switching mode for providing the peak power efficiencies of 94.4% and 93.6%, respectively. Compared with the state-of-the-art counterparts, this work is the only integrated DC–DC-based dimmable LED driver to demonstrate auto-configurable hard- and soft-switching capability achieving high power efficiency and current accuracy over the widest input voltage range and the largest number of series-connected output LEDs.

Cost-Effective Solution of Input Voltage Stabilizer of Auxiliary Drive Converter for Traction Vehicles

This paper describes a prospective design concept of a hard switching input voltage stabilizer for the auxiliary drives converters of dc catenary fed light traction vehicles. Auxiliary drives are mostly dedicated to generate standard power grid that supplies various on-board equipment and charging on-board batteries. The input voltage stabilizer (IVS) is the first input block of auxiliary drives. This block defines the voltage level of the consequent dc/dc isolated converter (IC). The main aim of this paper is to present the reader with the design of a low-cost variant of the voltage stabilizer. The described input voltage stabilizer is designed as a buck (step-down) or boost (step-up) converter, operating with an input catenary voltage range of 400 (VDC) to 950 VDC. The new fast, discrete IGBT H3 transistors and SiC diodes allow switching frequency from 20 kHz to 30 kHz in a hard switching mode with power rated up to 22 kW. DOI: http://dx.doi.org/10.5755/j01.eee.21.6.13752

Cost-Effective Solution of Input Voltage Stabilizer of Auxiliary Drive Converter for Traction Vehicles

This paper describes a prospective design concept of a hard switching input voltage stabilizer for the auxiliary drives converters of dc catenary fed light traction vehicles. Auxiliary drives are mostly dedicated to generate standard power grid that supplies various on-board equipment and charging on-board batteries. The input voltage stabilizer (IVS) is the first input block of auxiliary drives. This block defines the voltage level of the consequent dc/dc isolated converter (IC). The main aim of this paper is to present the reader with the design of a low-cost variant of the voltage stabilizer. The described input voltage stabilizer is designed as a buck (step-down) or boost (step-up) converter, operating with an input catenary voltage range of 400 (VDC) to 950 VDC. The new fast, discrete IGBT H3 transistors and SiC diodes allow switching frequency from 20 kHz to 30 kHz in a hard switching mode with power rated up to 22 kW. DOI: http://dx.doi.org/10.5755/j01.eee.21.6.13752

PWM Control for Actively Clamped Resonant DC-Link Inverter on Soft-Switching

Due to the active inverter in industrial application, if use hard switching mode, not only may have the switch losses, but also may produce electromagnetic interference and harmonic, these power quality is affected. This paper presents the design of a soft-switching active inverter, that active clamped resonant DC-link inverter topology was used on the main circuit, the voltage space vector pulse width modulation (SVPWM) control mode was used on control circuit, using TMS320LF2407DSP programming, while the AT89C51 was responsible for liquid crystal display task, data exchanged and coordinated between double CPU. The experimental results show that, the device switching-losses can effectively reduce, the switching frequency can improve, input power quality can improve.

Characterization of 6.5 kV IGBTs for High-Power Medium-Frequency Soft-Switched Applications

Medium voltage high-power applications are usually realized using high voltage semiconductors (3.3 kV and above) operated in the hard switching mode with low switching frequencies (several hundreds of hertz). However, for high-power dc-dc converters employing a transformer for galvanic isolation, it is attractive to increase the switching frequency so that the transformer size can be reduced. An increase of the switching frequency implies an increase of the switching losses, and this has to be mitigated somehow, usually by choice of resonant topologies or soft switching techniques. Main focus of the paper is on the operation of the insulated gate bipolar transistor (IGBT) within a high-power dc-dc LLC resonant converter, in order to explore interactions between semiconductor and circuit properties, which both must be simultaneously considered in order to achieve the best utilization of a high voltage power semiconductor operating at higher switching frequencies. For these purposes, switching properties of a standard 6.5 kV IGBT are compared with switching properties of two different optimized versions of a 6.5 kV IGBT. Experimental results are included to support theoretical considerations and findings.

A Novel Soft-Switching Bidirectional DC–DC Converter With Coupled Inductors

This paper presents a novel topology for a nonisolated bidirectional dc-dc converter with soft-switching capabilities, which usually operates at a zero-voltage-switching (ZVS) condition. A nonisolated dc-dc converter combines a buck converter and a backward boost converter into one circuit, which consists of a half-bridge power switch, an inductor, and capacitors. In order to realize ZVS conditions, the proposed converter utilizes a coupled inductor, a small independent inductor, and auxiliary switches and diodes. Due to ZVS, switching stress on switch components is reduced, and the reverse recovery problem of MOSFET antiparallel body diodes is also eliminated. Moreover, the operating modes of the proposed converter can be switched between a ZVS mode and a conventional hard-switching mode on the basis of load conditions. The soft-switching mode is for heavy loads, and the hard-switching mode is for light-load conditions. Therefore, the highest efficiency can be obtained at almost all load ranges. The detailed theoretical analyses in each mode are presented, and a 1-kW prototype is also built to verify the principle of the circuit and the theoretical analysis.

Comparison of 4.5-kV Press-Pack IGBTs and IGCTs for Medium-Voltage Converters

Recently developed insulated-gate bipolar transistor (IGBT) press-pack (PP) devices with a blocking voltage of 4.5 kV are being used in medium-voltage converters as an alternative to integrated gate-commutated thyristors (IGCTs). This paper presents an overview of PP packaging and both semiconductor technologies. A quantitative comparison of these devices is achieved through measurements for a 4.5-kV 1.2-kA IGBT and a 4.5-kV 4-kA IGCT. The laboratory test bench for the switching transient characterization at a dc-link voltage of 2.5 kV and currents up to 3 kA is described. Conduction, blocking, and switching behavior for junction temperatures up to 125 °C are investigated. The IGCT and the IGBT are tested using a di/dt-limiting clamp circuit. In addition, the IGBT is tested in hard switching mode.

Reliability Estimation of Three Single-Phase Topologies in Grid-Connected PV Systems

This paper presents the reliability estimation of the power stages in three grid-connected photovoltaic systems. The circuits analyzed are an integrated topology, a two-stage configuration, and a three-stage one, all commutating in the hard-switching mode. The reliability-related parameters, such as the failure rate, are calculated following the procedure outlined in MIL-HDBK 217. A comparison between the topologies is performed, and both the components and the stress factor with the highest contribution to the failure rate are identified. The methods to calculate junction temperature variations are included.