H. Alan Mantooth

Wide Bandgap Technologies and Their Implications on Miniaturizing Power Electronic Systems

The current state of wide bandgap device technology is reviewed and its impact on power electronic system miniaturization for a wide variety of voltage levels is described. A synopsis of recent complementary technological developments in passives, integrated driver, and protection circuitry and electronic packaging are described, followed by an outline of the applications that stand to be impacted. A glimpse into the future based on the current technological trends is offered.

Datasheet Driven Silicon Carbide Power MOSFET Model

A compact model for SiC Power MOSFETs is presented. The model features a physical description of the channel current and internal capacitances and has been validated for dc, CV, and switching characteristics with measured data from a 1200-V, 20-A SiC power MOSFET in a temperature range of 25°C to 225°C. The peculiar variation of on-state resistance with temperature for SiC power MOSFETs has also been demonstrated through measurements and accounted for in the developed model. In order to improve the user experience with the model, a new datasheet driven parameter extraction strategy has been presented which requires only data available in device datasheets, to enable quick parameter extraction for off-the-shelf devices. Excellent agreement is shown between measurement and simulation using the presented model over the entire temperature range.

Switching characteristics of SiC JFET and Schottky diode in high-temperature dc-dc power converters

This paper reports on SiC devices operating in a dc-dc buck converter under extremely high ambient temperatures. To this end, the authors packaged SiC JFET and Schottky diodes in thermally stable packages and built a high-temperature inductor. The converter was tested at ambient temperatures up to 400°C. Although the conduction loss of the SiC JFET increases slightly with increasing temperatures, the SiC JFET and Schottky diode continue normal operation because their switching characteristics show minimal change with temperature. This work further demonstrates the suitability of the SiC devices for high-temperature power converter applications.

Novel nonlinear control of Dual Active Bridge using simplified converter model

This paper addresses the control of a Dual Active Bridge (DAB) dc/dc converter. Closed-loop control of the output voltage is achieved by a novel nonlinear technique that separates the control algorithm into a linearization stage and a linear control law. The resulting DAB is capable of bidirectional power flow, and the transformer isolation makes it suitable for a wide variety of applications. The size of the isolation transformer is greatly reduced due to high-frequency (HF) operation resulting in high power densities. Also, switching losses are reduced since zero-voltage switching (ZVS) takes place over a range of operating conditions. Simulation and experimental results are presented for a 400V-400V, 10-kHz, and 10kW prototype.

Compact Modeling of LDMOS Transistors for Extreme Environment Analog Circuit Design

The cryogenic characterization (93 K/-180°C to 300 K/27°C) and compact modeling of a high-voltage (HV) laterally diffused MOS (LDMOS) transistor that exhibits carrier freeze-out are presented in this paper. Unlike low-voltage MOS devices, it was observed that HVMOS structures experience freeze-out effects at much higher temperatures, resulting in an output current roll-off beyond a transition temperature. Standard compact models generally do not guarantee performance below 218 K (-55°C), and freeze-out effects are certainly not incorporated in them. This causes the models to fail to track at lower temperatures, and designers relying on these models would be misled. In this paper, the temperature-scaling equations of the MOS Model 20 LDMOS model are modified to reflect the device operation down to 93 K, which is sufficient for designing sensor interface circuitry for lunar applications. The model is then validated against an LDMOS device designed by engineers at the Jet Propulsion Laboratory, using the IBM SiGe 5AM process. A modified parameter extraction procedure has also been developed. This generalized approach is compact model friendly and can also be implemented for other standard models. Analog circuits designed with this new model are currently being tested at the International Space Station.

A Physics-Based Model for a SiC JFET Device Accounting for the Mobility Dependence on Temperature and Electric Field

In this work a physical model for a SiC Junction Field Effect Transistor (JFET) is presented. The novel feature of the model is that the mobility dependence on both temperature and electric field is taken into account. This is particularly important for high-current power devices, where the maximum conduction current is limited by drift velocity saturation in the channel. The model equations are described in detail, emphasizing the differences introduced by the field-dependent mobility model. The model is then implemented in Pspice. Both static and dynamic simulation results are given. The results are validated with experimental results under static conditions and under resistive switching conditions.

Design and evaluation of a universal power router for residential applications

The next generation universal power routing system has been developed for residential use; compared to energy management systems that already exist, this system effectively reduces the need for human interaction through automation of home power usage. The Smart Green Power Node (SGPN) manages on-site energy resources coupled at a DC link that feeds a bi-directional grid-tied inverter supplying loads within a home via a 240 V AC bus. It incorporates all relevant data such as weather, Time of Use pricing, appliance energy usage, user preferences, status of on-site resources, and communications to intelligently manage the power flow between those on-site energy resources, the electric grid, and the loads. Additionally, it has the capability to maintain power to the home in the event of a power outage and will continue to intelligently provide power while islanded from the grid. The system functionality has been verified through simulations and a prototype has been developed and evaluated.

Reliable and repeatable bonding technology for high temperature automotive power modules for electrified vehicles

This paper presents the feasibility of highly reliable and repeatable copper–tin transient liquid phase (Cu–Sn TLP) bonding as applied to die attachment in high temperature operational power modules. Electrified vehicles are attracting particular interest as eco-friendly vehicles, but their power modules are challenged because of increasing power densities which lead to high temperatures. Such high temperature operation addresses the importance of advanced bonding technology that is highly reliable (for high temperature operation) and repeatable (for fabrication of advanced structures). Cu–Sn TLP bonding is employed herein because of its high remelting temperature and desirable thermal and electrical conductivities. The bonding starts with a stack of Cu–Sn–Cu metal layers that eventually transforms to Cu–Sn alloys. As the alloys have melting temperatures (Cu3Sn: > 600 °C, Cu6Sn5: > 400 °C) significantly higher than the process temperature, the process can be repeated without damaging previously bonded layers. A Cu–Sn TLP bonding process was developed using thin Sn metal sheets inserted between copper layers on silicon die and direct bonded copper substrates, emulating the process used to construct automotive power modules. Bond quality is characterized using (1) proof-of-concept fabrication, (2) material identification using scanning electron microscopy and energy-dispersive x-ray spectroscopy analysis, and (3) optical analysis using optical microscopy and scanning acoustic microscope. The feasibility of multiple-sided Cu–Sn TLP bonding is demonstrated by the absence of bondline damage in multiple test samples fabricated with double- or four-sided bonding using the TLP bonding process.

A family of CMOS analog and mixed signal circuits in SiC for high temperature electronics

This paper describes the simulation and test results of a family of analog and mixed signal circuits in silicon carbide CMOS technology at temperatures of 300°C and above. As SiC and wide bandgap devices in general grow in popularity for efficient and stable operation in high temperature and harsh environment applications, CMOS SiC integrated circuits can open up a new frontier of opportunity for miniaturization and system dependability. The building block circuits presented here can serve as the basis of rugged SiC system-on-chips for extreme environment applications.

Modular multilevel converter with high-frequency transformers for interfacing hybrid DC and AC microgrid systems

Recently, concepts of both ac and dc microgrids have been proposed for future energy systems. A novel converter topology which has three ports: 12 kV ac, 22 kV dc and 400 V dc for future hybrid ac and dc microgrid systems is presented in this paper. Each port has the capability of bi-directional power flow which is required in future hybrid ac and dc microgrids. The 400 V dc bus, which is connected to distributed energy resources, injects/draws power to/from both the ac grid and the dc grid through solid-state transformers. The topology avoids the use of line-frequency transformers which are considered to be expensive and bulky. Because the hybrid converter is connected to both the ac grid and the dc grid, enhanced reliability is achieved. A modular design of the sub-module of the modular multilevel converter is proposed for reducing the sub-module failure probability. Extensive time-domain simulations using Matlab/Simulink™ are presented demonstrating the feasibility of the proposed topology.