Jerry L. Hudgins

An assessment of wide bandgap semiconductors for power devices

An advantage for some wide bandgap materials, that is often overlooked, is that the thermal coefficient of expansion (CTE) is better matched to the ceramics in use for packaging technology. It is shown that the optimal choice for uni-polar devices is clearly GaN. It is further shown that the future optimal choice for bipolar devices is C (diamond) owing to the large bandgap, high thermal conductivity, and large electron and hole mobilities. A new expression relating the critical electric field for breakdown in abrupt junctions to the material bandgap energy is derived and is further used to derive new expressions for specific on-resistance in power semiconductor devices. These new expressions are compared to the previous literature and the efficacy of specific power devices, such as heterojunction MOSFETs, using GaN are discussed.

Two-step parameter extraction procedure with formal optimization for physics-based circuit simulator IGBT and p-i-n diode models

A practical and accurate parameter extraction method is presented for the Fourier-based-solution physics-based insulated gate bipolar transistor (IGBT) and power diode models. The goal is to obtain a model accurate enough to allow switching loss prediction under a variety of operating conditions. In the first step of the extraction procedure, only one simple clamped inductive load test is needed for the extraction of the six parameters required for the diode model and of the 12 and 15 parameters required for the nonpunch-through (NPT) and punch-through (PT) IGBT models, respectively. The second part of the extraction procedure is an automated formal optimization step that refines the parameter estimation. Validation with experimental results from various structures of IGBT demonstrates the accuracy of the proposed IGBT and diode models and the robustness of the parameter extraction method.

Exploration of Power Device Reliability using Compact Device Models and Fast Electro-Thermal Simulation

This paper presents the application of compact insulated gate bipolar transistor and p-i-n diode models, including features such as local lifetime control and field-stop technology, to the full electrothermal system simulation of a hybrid electric vehicle converter using a lookup table of device losses. The vehicle converter is simulated with an urban driving cycle (the federal urban driving schedule), which is used to generate transient device temperature profiles. A methodology is also described to explore the converter reliability using the temperature profile, with rainflow cycle counting techniques from material fatigue analysis. The effects of ambient temperature, driving style, and converter design on converter reliability are also investigated.

New Developments in Gallium Nitride and the Impact on Power Electronics

Wide bandgap III-nitride semiconductor materials possess superior material properties as compared to silicon, GaAs and other III-V compound materials. Recent achievements in gallium nitride (GaN) technology for optoelectronics have resulted in ultra-bright blue light emitting diodes and lasers, ultraviolet emitters, and solar-blind optical detectors. In the electronic area, drastic improvement of microwave device performance has been achieved, yielding record high power densities of 20-30 W/mm. Novel applications of these materials in high-power electronics for switching, energy conversion and control are just emerging. This paper provides an overview of the state-of-the-art III-nitride wide bandgap technologies and it explores power electronic applications while illustrating the enormous potential that GaN based devices have for overcoming the major challenges of power electronics in the 21st century. The paper discusses the unique material and device properties of GaN-based semiconductors that make them promising for high-power, high-temperature applications. These include high electron mobility and saturation velocity, high sheet carrier concentration at heterojunction interfaces, high breakdown voltages, and low thermal impedance (when grown over SiC or bulk AIN substrates). The chemical inertness and radiation hardness of nitrides are other key properties. As applied to power electronics, the Ill-Nitride technology allows for high-power switching with sub-microsecond and nano-second switching times. The paper will present the innovations that further improve the performance of high-power DC-DC converters, switches and other building blocks. These include novel insulated gate HFET design that significantly expands the allowable input voltage amplitude, further increases the device peak currents, and most importantly, tremendously improves the large-signal stability and reliability. Insulated gate switching devices have been shown to operate at up to 300 degC with no noticeable parameter degradation. Novel monolithic integrated circuits of high-power switches and DC-DC converters and their performance parameters will be presented. The paper also discusses the major challenges associated with modern GaN technology and work in progress to overcome them

Transient Electrothermal Simulation of Power Semiconductor Devices

In this paper, a new thermal model based on the Fourier series solution of heat conduction equation has been introduced in detail. 1-D and 2-D Fourier series thermal models have been programmed in MATLAB/Simulink. Compared with the traditional finite-difference thermal model and equivalent RC thermal network, the new thermal model can provide high simulation speed with high accuracy, which has been proved to be more favorable in dynamic thermal characterization on power semiconductor switches. The complete electrothermal simulation models of insulated gate bipolar transistor (IGBT) and power diodes under inductive load switching condition have been successfully implemented in MATLAB/Simulink. The experimental results on IGBT and power diodes with clamped inductive load switching tests have verified the new electrothermal simulation model. The advantage of Fourier series thermal model over widely used equivalent RC thermal network in dynamic thermal characterization has also been validated by the measured junction temperature.

Review of technologies for current-limiting low-voltage circuit breakers

Conventional air-magnetic circuit breakers, which are widely used in low-voltage applications, utilize magnetic forces that are produced by blowout coils, the geometry of the arcing contacts, or both. The magnetic forces act to push the arc off the contacts into an arc chute, which consists of a number of metal plates. The arc chute causes the arc to be split into a number of smaller arcs, thereby facilitating the process of extinguishing the arc. In the last 20 years, the technology of circuit breakers has dramatically advanced, now including mature devices based on gas-blast (such as SF/sub 6/) and vacuum interruption. At the same time, the technology of power electronic devices has evolved rapidly, leading to suggestions of a purely static circuit breaker based on solid-state electronic devices. Recently, several different proposals have appeared for current-limiting devices to be used in conjunction with or in replacement of conventional circuit breakers. The technologies involved in these proposals have ranged from very familiar (series reactors) to quite innovative (conductive polymer devices). Several of these proposed technologies have been used to a limited extent in commercial products, but they are very likely to see increasing applications as the technology matures. This paper begins with a short review of conventional circuit breaker action for background, then reviews the recent literature for current-limiting technologies that could be applied to low-voltage electric power systems. The paper concludes with a description of work underway for further development of conductive polymer current limiters.

Parameter extraction for a physics-based circuit simulator IGBT model

A practical parameter extraction method is presented for the Fourier-based-solution physics-based IGBT model. In the extraction procedure, only one simple clamped inductive load test is needed for the extraction of the eleven and thirteen parameters required for the NPT and PT IGBT models, respectively. Validation with experimental results from various structure IGBTs demonstrates the accuracy of the proposed IGBT model and the robustness of the parameter extraction method.

Thermal analysis of high-power modules

A highly descriptive method for displaying heat flow in power modules is presented. Heat flow is studied for three different transistor-stack types: direct bond copper (DEC), thick-film printed substrate, and insulated metal substrate (IMS). DEC and thick film are thermally superior to IMS, but IMS shows potential. In addition, the effect of case-to-sink interface conductivity on heat flow is studied and shown to be of extreme importance in a proper thermal simulation.

Parameter extraction for a power diode circuit simulator model including temperature dependent effects

Power electronics designers need accurate models of power diodes to perform simulations of the systems they are designing. The diode models should be accurate under a wide variety of operating conditions. In particular temperature dependencies should be accurately modeled. Physics-based models appear to be the best choice to meet these requirements. On the other hand, complicated parameter extraction procedures discourage use of these models by practicing engineers. In this work we explore the possibility of using a sophisticated physics-based diode model utilizing at most three parameters obtained directly or estimated from the manufacturers data sheets. In order to validate the proposed approach, several diodes with different characteristics are tested under different conditions and a wide temperature range from -150 to 150/spl deg/C. Experimental results are compared with simulations.

Modeling of IGBT Resistive and Inductive Turn-On Behavior

Although insulated-gate bipolar-transistor (IGBT) turn-on losses can be comparable to turn-off losses, IGBT turn-on has not been as thoroughly studied in the literature. In the present work IGBT turn on under resistive and inductive load conditions is studied in detail through experiments, finite element simulations, and circuit simulations using physics-based semiconductor models. Under resistive load conditions, it is critical to accurately model the conductivity-modulation phenomenon. Under clamped inductive load conditions at turn-on there is strong interaction between the IGBT and the freewheeling diode undergoing reverse recovery. Physics-based IGBT and diode models are used that have been proved accurate in the simulation of IGBT turn-off.