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A novel algorithm for automatic behavioral model topology formulation (MTF) is described in this paper. Several new terms are defined to support this formulation approach. The algorithms for determining the controllability and equivalence of branches are developed. The identification of differential pairs and current mirror structures is implemented automatically. Some other algorithms identify a subset of nodes in circuits that are extracted and modeled, while the other nodes will be collapsed. The MTF algorithm then is applied to construct a new signal-path graph, i.e., forming an equivalent circuit that has the ability to represent the behavior of the original circuit in a much-simplified form. This algorithm is implemented in a fully automated modeling tool, ASCEND, which starts from the netlist description of a circuit and generates a differential-algebraic-equation-based model. These models are able to represent static and dynamic behaviors with excellent accuracy and significant simulation speedup. The details of the MTF algorithm are described. Examples of applying the MTF algorithm for behavioral modeling are given. [ABSTRACT FROM AUTHOR]

Distributed energy resources (DERs) are becoming integral components of electric power distribution systems. Inmost cases, an isolated dc-dc converter forms part of the interface required to connect the DER output to the distribution system. Operation of the converter at high switching frequencies results in size reduction of passive components at the expense of increased switching losses. However, silicon carbide (SiC) power devices have the potential of operating at high switching frequencies without significant loss penalty because of their fast switching times and ability to work at high temperatures when compared to similar Si devices. SiC diodes have already displayed the ability to offer more ideal diode behavior than Si diodes. Engineering samples of SiC MOSFETs are depicting lower switching losses and conduction losses over Si MOSFETs. This display is making SiC devices attractive for dc-dc converters used to connect DERs to the distribution system. This paper particularly deals with the design of a 300.W 100-kHz dc-dc full-bridge converter using zero-voltage zero-current switching for comparison of SiC MOSFETs and diodes against Si MOSFETs and diodes. [ABSTRACT FROM AUTHOR]

An algorithm for determining when electrical circuit poles and zeros (i.e., roots) are topologically localized to a node or coupled-pair of nodes is described. Discovering this relationship provides insight to designers for circuit optimization, and is a basis upon which nonlinear dynamic behavioral models can be built. This root localization algorithm, the main contribution of this paper, facilitates the creation of models that more accurately reflect the distinctive behavior of a circuit. This is accomplished by identifying when poles and zeros can be modeled as localized effects whose values change with circuit operating conditions. The underlying modeling approach is described to provide a context for this research. The algorithm is illustrated through several examples. [ABSTRACT FROM AUTHOR]

The study aimed to investigate the underlying physics limiting the temperature stability and performance of non-surface passivated Al0.34Ga0.66N/GaN Hall effect sensors, including contacts, under atmospheric conditions. The results obtained from analyzing the microstructural evolution in the Al0.34Ga0.66N/GaN Hall sensor heterostructure were found to correlate with the electrical performance of the Hall effect sensor. High-resolution x-ray photoelectron spectroscopy studies revealed the signature of surface oxidation in the GaN cap layer, as well as a slight out-diffusion of "Al" from the AlGaN barrier layer. To prevent the formation of a bumpy surface morphology at the Ohmic contact, we investigated the impact of "Pt" top Ohmic contacts. The application of a top "Pt" contact stack resulted in a smooth Ohmic contact surface and provided evidence that the bumpy surface morphology in Au-based Ohmic contacts is due to the formation of an Al-Au viscous alloy during rapid thermal annealing. In the early stages of thermal aging, the small drop in contact resistivity stabilized with subsequent thermal aging past the initial 550 h at 200 °C. The outcome is that the Al0.34Ga0.66N/GaN Hall effect sensors, even without surface passivation, exhibited a stable response to applied magnetic fields with no sign of significant degradation after 2800 h of thermal aging at 200 °C under atmospheric conditions. This observed stability in the Hall sensor without surface passivation can be attributed to a self-imposed surface oxidation of the cap layer during the early stages of aging, which serves as a protective layer for the device during subsequent extended periods of thermal aging at 200 °C. [ABSTRACT FROM AUTHOR]

Power module heat dissipation with spatial inhomogeneity and induced nonuniform temperature distribution presents a challenging concern for system reliability due to thermo-mechanical stresses. These reliability challenges are especially important for nonplanar designs using 3-D packaging principles. Here, we develop a heat spreader thermal switch capable of actively reducing temperature gradients between silicon carbide (SiC) devices in a three-level T-type power converter, which can change depending on electronic operating conditions. The heat spreader thermal switch consists of a stainless-steel (SS) heat spreader and a copper sliding switch embedded within the spreader. Heat transfer from the SiC devices and within the spreader can be controlled by moving the slider between positions within the spreader. To understand heat transfer mechanisms and design the heat spreader thermal switch, we conducted 3-D finite element method simulations to calculate the minimum attainable temperature difference between SiC devices. We used the finite element simulation to quantify the reduction in junction temperature swing during dynamic operation and coupled the results to the Coffin–Manson reliability model to quantify lifetime to failure. We integrated the heat spreader thermal switch with one phase of a three-phase T-type converter and demonstrated isothermalization at different working conditions. At 2.4-kW converter power, each hot SiC device dissipated 4.7 W of heat, resulting in a device case temperature of 43 °C, with each cold SiC device dissipating 1.7 W at 38 °C. The device-to-device temperature difference was decreased from 5 °C to 0 °C by moving the switch a distance of 20 mm. Finite volume method (FVM) simulations of the conjugate heat transfer problem validate the experimental results and support analysis of key performance parameters. This work demonstrates successful isothermalization of a power converter with an active heat spreader thermal switch and develops simulation and design guidelines for successful electro-thermal codesign and implementation of thermal switches for other electronics applications for which isothermalization and enhanced device reliability is a key issue. [ABSTRACT FROM AUTHOR]

Editorial. Introduces the articles published in the February 2003 issue of the periodical 'IEEE Transactions on Computer-Aided Design of Integrated Circuits (IC) and Systems. Improvement of IC design productivity, performance optimization and circuit reliability; Derivation of state-space model for class-E power amplifiers; Modelling techniques and algorithms.

Although LLC converters are attractive in industrial applications due to its advantages of soft switching, high efficiency, and simple control, in wide voltage gain range applications, large switching frequency operating range is required, which may cause the loss of soft switching operation and existence of control instability issue. In this article, a novel LLC converter with two LLC resonant tanks is proposed. The proposed converter has three operation modes, namely, dual full-bridge operation mode, full-bridge operation mode, and half-bridge operation mode, which can cover the high voltage gain range, medium voltage gain range, and low voltage gain range operations, respectively. The operational principles of the proposed converter are presented, and brief design considerations are discussed. A 250 W experimental prototype with six times input voltage range (50–300 V) was built to validate the theoretical analysis of the proposed converter. Comparisons among different LLC topologies for wide voltage gain range applications are made. [ABSTRACT FROM AUTHOR]

The article discusses various reports published within the issue, including "Simulation and development environment for mobile 3D graphics architecture," by Won-Jong Lee and colleagues and "Modeling tools built upon the HDL foundation," by Alan Mantooth and colleagues.

A comprehensive overview of the advancements, challenges, and prospects of silicon carbide (SiC) complementary metal-oxide-semiconductor (CMOS) technology is presented. As the demand for high-performance and energy-efficient electronic devices continues to grow, SiC has emerged as a promising material due to its unique properties. The paper aims to provide a thorough understanding of the state-of-the-art developments in SiC CMOS technology. The paper delves into the key features of SiC and its compatibility with CMOS processing techniques. It highlights the challenges associated with SiC CMOS technology, such as substrate quality, interface states, and process integration. Examples of CMOS circuitry that have been successfully designed, fabricated, and tested are provided. [ABSTRACT FROM AUTHOR]

This article puts forward a hybrid model predictive control (H-MPC) for an inner-interleaved hybrid multilevel converter (IHMC). The sign patterns of the original and shifted reference vectors in the original and virtual space vector diagrams (VSVDs) are used, respectively, to realize the phase-disposition pulsewidth modulation (PWM) and determine the low-frequency switching states. Then, the three adjacent vectors are selected in the second-layer VSVD and the optimal current tracking is safeguarded by the duty cycle optimization of the three adjacent vectors. Finally, through applying the phase-shifted PWM to the two interleaved legs, a constant and doubled equivalent switching frequency can be achieved, which further paves the way for dc-link and floating capacitor voltages balancing and circulating current mitigation with the use of the straightforward duty cycle adjustments. The proposed H-MPC enables the decoupling of the low- and high-frequency stages in the IHMC and also reduces both output current ripples and computational burden while achieving a constant switching frequency simultaneously. Comprehensive simulation and experimental studies on an all silicon carbide prototype verify the effectiveness of the proposed control strategy. [ABSTRACT FROM AUTHOR]

This paper reports high-temperature optocouplers for signal galvanic isolation. Low temperature co-fired ceramic (LTCC) technology was used in the design and fabrication of the high-temperature optocoupler package. The optimal coupling behaviors, driving capabilities and response speed of the optocouplers were concentrated and investigated in this paper. Emitters and detectors with different emission and spectral wavelengths were studied to achieve optimal coupling behaviors. Relatively high coupling efficiency is achieved with emitters and detectors of emission and spectral wavelength in the red spectrum (i.e., 620–750 nm), leading to higher current transfer ratios (CTR). To further enhance the electrical performance, optocouplers with multiple detectors in parallel were designed and fabricated. CTR, leakage current and response speed (i.e., propagation delay, rise time and fall time) of the optocouplers were characterized over a range of temperatures from 25 to 250 °C. The CTR degrades at high temperatures, while the leakage current and response speed show little degradation with varying temperatures. Furthermore, the behaviors of the optocouplers with varying temperatures are modeled and analyzed. [ABSTRACT FROM AUTHOR]

This article puts forward a hybrid model predictive control (H-MPC) that enables the decoupling of low- and high-frequency stages in a seven-level hybrid multilevel converter (7L-HMC). It first uses the sign pattern of the reference voltage vector to determine switching states of the low-frequency stage. Next, the reference vector is shifted to the internal hexagon of the original space vector diagram, which is thereby converted to a 120° oblique coordinate system, where the adjacent vectors can be rapidly selected. Then, the optimal current tracking is primarily safeguarded by the duty cycle optimization of the three adjacent vectors. Finally, an optimized symmetric switching sequence minimizing the dc voltage deviation over one control iteration is selected through the assessment of possible switching sequences that are subject to the chosen vectors with optimal duty cycles. The proposed H-MPC method can reduce both the current ripple and computational burden while achieving a constant switching frequency. Comprehensive simulation and experimental comparisons on an all-silicon-carbide 7L-HMC prototype verify the effectiveness of the proposed H-MPC. [ABSTRACT FROM AUTHOR]

This article presents the design and demonstration of an all silicon carbide (SiC) 2×250 kW dual inverter for heavy-duty traction applications. Through the use of a formal electrothermal-control co-design approach, the maximum power density of the proposed inverter system is 60 kW/L, which is accomplished by. More specifically, to analyze the thermal performance of the inverter, a lumped thermal model is developed based on the characteristics of the power modules and the cold plate. To analyze the complicated interaction between the power losses and module junction temperatures, a closed-loop iterative estimation scheme is proposed to estimate the inverter power loss and module junction temperature. Based on the proposed thermal model and estimation scheme, a detailed optimization procedure on the selection of switching frequency and dc-link capacitor is presented to maximize power density. Furthermore, design optimization of the busbar was conducted to minimize the stray inductance, thus reducing the voltage overshoot during switching transients. Comprehensive experimental studies were performed on a physical converter prototype built based on the optimization results, which validate both the effectiveness of the presented design approach. [ABSTRACT FROM AUTHOR]

Abstract: Silicon carbide Schottky, merged PiN Schottky (MPS), and PiN diode technologies are modeled for on-state and reverse recovery conditions. The on-state operation of the PiN diode is modeled through four unique regimes of operation, including current densities resulting in emitter recombination, which results in a stored charge plateau during reverse recovery of SiC PiN diodes. An expression for the moving boundary redistribution capacitance is developed to accurately describe the reverse recovery process in PiN diodes. Furthermore, the extraction of stored charge and junction capacitance from transient reverse recovery measurements is also demonstrated for all diode technologies. The on-state operation of Schottky and merged PiN Schottky diodes is described and a method to model the surge current in MPS diodes is discussed. The performance of the model is demonstrated for a commercially available 600V, 4A Schottky diode and a 10kV, 7.5A PiN diode. Measurements demonstrating the extraction of model parameters and model validation results are included. [Copyright &y& Elsevier]

As a critical energy-conversion system component, power semiconductor modules and their layout optimization has been identified as a crucial step in achieving the maximum performance and density for wide bandgap technologies (i.e., GaN and SiC). New packaging technologies are also introduced to produce reliable and efficient multichip power module (MCPM) designs to push the current limits. The complexity of the MCPM layout is surpassing the capability of a manual, iterative design process to produce an optimum design with agile development requirements. An electronic design automation tool called PowerSynth has been introduced with on-going research toward enhanced capabilities to speed up the optimized MCPM layout design process. As a part of this continuing research, in PowerSynth v1.9, a constraint-aware layout engine has been developed, which enables integrating heterogeneous components, handling complex geometry, exploring a larger solution space, improved success rate, and providing options for multiobjective optimization algorithms. The layout engine is generic, scalable, and efficient in performing electro-thermal optimizations on both 2-D and 2.5-D power modules. To validate these enhanced design capabilities, a 2.5-D full-bridge power module layout is designed, optimized, fabricated, and tested with measurement results matching closely with model prediction. This result closes the loop in the power electronics design process with an experimentally validated module design automation flow. [ABSTRACT FROM AUTHOR]

In this article, an efficiency-oriented hybrid duty modulation (HDM) scheme is proposed for the dual active bridge (DAB) converter that can reduce the inductor root-mean-square (rms) current and extend the switch soft-switching range. First, a complete description of the combination forms of different modulation schemes is presented considering the allocation of the zero-voltage portion. A unified description for these combination forms is obtained in the frequency domain. Second, the symmetric–symmetric duty modulation (SSDM) scheme and asymmetric–symmetric duty modulation (A2SDM) scheme are established to minimize the inductor rms current by considering its fundamental component. Third, the characteristics of SSDM, A2SDM, and the traditional phase shift modulation schemes are compared from several aspects, mainly including the inductor rms current and the soft-switching performance. Furthermore, the loss breakdown analysis results for the three modulation schemes are presented and compared. According to these results, the HDM scheme is proposed to improve the overall efficiency of the DAB converter. Finally, an experimental prototype was built with a peak efficiency of 97%, which validates the effectiveness of the proposed modulation scheme. [ABSTRACT FROM AUTHOR]

The silicon carbide (SiC) devices have faster switching speed than that of the conventional silicon (Si) devices, which however may cause excessive device voltage overshoot. Larger gate resistance can help to restrain the overshoot, it however slows down the switching speed and increases switching losses. There are other methods that can mitigate the voltage overshoot, e.g., using low-inductance busbars, adding snubber circuits, etc. In this article, the busbar design for a 250-kW SiC three-level T-type inverter is investigated. The current commutation loops (CCLs) are first analyzed using a single-phase equivalent circuit. Then the detailed busbar design methods, especially a 3-D busbar design concept, are proposed to select the optimal stacking order for the multilayer laminated busbar and to address constraints posed by the physical terminal arrangements of SiC modules and dc-link capacitors. The stray inductance in each CCL is extracted via a finite element analysis and validated on the actual inverter busbar prototypes using an impedance analyzer. To further minimize the busbar stray inductance, a hybrid busbar structure with printed circuit board based buffer circuit using high-frequency decoupling capacitors is designed and evaluated in this article. Finally, the effectiveness of the designed busbars as well as the buffer circuit are validated using experimental studies. [ABSTRACT FROM AUTHOR]

The cascaded H-bridge (CHB) inverter is one of the most attractive multilevel topologies for renewable energy applications. Due to the fact that CHB inverters employ a large number of components, they suffer from a higher probability of fault, which reduces the system reliability. A fault-tolerant operation for a CHB inverter is described in this article. New features ensure reliable and robust operation of the converter in the event of a fault. The proposed strategy uses an additional cross-coupled CHB (X-CHB) unit in companion with the existing CHB units to support the output voltage and ensure continuity of operation in the event of an open/short-circuit fault. The operation of the proposed X-CHB inverter is described in detail. Simulation and experimental verification of the proposed concept are demonstrated using a seven-level CHB. Both simulation and experimental results confirm the fault-tolerant operation of the X-CHB for a battery energy storage system in case of switch faults. [ABSTRACT FROM AUTHOR]