Zach Cole

A High-Density, High-Efficiency, Isolated On-Board Vehicle Battery Charger Utilizing Silicon Carbide Power Devices

This paper presents an isolated on-board vehicular battery charger that utilizes silicon carbide (SiC) power devices to achieve high density and high efficiency for application in electric vehicles (EVs) and plug-in hybrid EVs (PHEVs). The proposed level 2 charger has a two-stage architecture where the first stage is a bridgeless boost ac-dc converter and the second stage is a phase-shifted full-bridge isolated dc-dc converter. The operation of both topologies is presented and the specific advantages gained through the use of SiC power devices are discussed. The design of power stage components, the packaging of the multichip power module, and the system-level packaging is presented with a primary focus on system density and a secondary focus on system efficiency. In this work, a hardware prototype is developed and a peak system efficiency of 95% is measured while operating both power stages with a switching frequency of 200 kHz. A maximum output power of 6.1 kW results in a volumetric power density of 5.0 kW/L and a gravimetric power density of 3.8 kW/kg when considering the volume and mass of the system including a case.

A 4H Silicon Carbide Gate Buffer for Integrated Power Systems

A gate buffer fabricated in a 2-μm 4H silicon carbide (SiC) process is presented. The circuit is composed of an input buffer stage with a push-pull output stage, and is fabricated using enhancement mode N-channel FETs in a process optimized for SiC power switching devices. Simulation and measurement results of the fabricated gate buffer are presented and compared for operation at various voltage supply levels, with a capacitive load of 2 nF. Details of the design including layout specifics, simulation results, and directions for future improvement of this buffer are presented. In addition, plans for its incorporation into an isolated high-side/low-side gate-driver architecture, fully integrated with power switching devices in a SiC process, are briefly discussed. This letter represents the first reported MOSFET-based gate buffer fabricated in 4H SiC.

A wide bandgap silicon carbide (SiC) gate driver for high-temperature and high-voltage applications

Limitations of silicon (Si) based power electronic devices can be overcome with Silicon Carbide (SiC) because of its remarkable material properties. SiC is a wide bandgap semiconductor material with larger bandgap, lower leakage currents, higher breakdown electric field, and higher thermal conductivity, which promotes higher switching frequencies for high power applications, higher temperature operation, and results in higher power density devices relative to Si [1]. The proposed work is focused on design of a SiC gate driver to drive a SiC power MOSFET, on a Cree SiC process, with rise/fall times (less than 100 ns) suitable for 500 kHz to 1 MHz switching frequency applications. A process optimized gate driver topology design which is significantly different from generic Si circuit design is proposed. The ultimate goal of the project is to integrate this gate driver into a Toyota Prius plug-in hybrid electric vehicle (PHEV) charger module. The application of this high frequency charger will result in lighter, smaller, cheaper, and a more efficient power electronics system.

High-frequency AC-DC conversion with a silicon carbide power module to achieve high-efficiency and greatly improved power density

This paper presents a high-frequency bridgeless boost converter that implements power factor correction (PFC) and is a part of a two-stage on-board battery charger. The converter benefits from the advanced properties of silicon carbide (SiC) power devices to achieve a high-density and high-efficiency design. The advantages gained with SiC devices are maximized with a multi-chip power module (MCPM) that was designed specifically for this application. The operation and design of the converter are discussed and a hardware prototype is developed. The performance is verified with a peak efficiency of 98.7% and a peak output power of 6.3 kW at a switching frequency of 250 kHz. The operational limits are also investigated up to a switching frequency of 1.2 MHz where a peak efficiency of 96.5% is achieved for an output power of 3 kW. The resulting system volumetric power density was found to be 11.1 kW/L and the gravimetric power density was 8.1 kW/kg.

SiC-MOSFET composite boost converter with 22 kW/L power density for electric vehicle application

A SiC-MOSFET composite boost converter for an electric vehicle power train application exhibits a volumetric power density of 22 kW/L and gravimetric power density of 20 kW/kg. The composite converter architecture, which is composed of partial-power boost, buck, and dual active bridge modules, leads to a 60% reduction in CAFE average losses, to a 280% improvement in power density, and to a 76% reduction in magnetics volume compared to the conventional Si-IGBT boost converter. These gains were achieved with the help of optimization based on a comprehensive loss model including SiC-MOSFET switching loss and magnetic losses based on the FEM method simulated in FEMM. Experimental results for the 22 kW/L SiC-MOSFET composite converter project 97.5% average efficiency on US06 driving cycle and a CAFE average efficiency of 97.8%.

Compact, high-temperature, single-level power modules for 10 to 25 kV DC link voltages using silicon carbide power electronics

Power modules designed explicitly for silicon carbide (SiC), single level power converters between 10 and 24 kV are presented. Using silicon power electronics, multi-level converters are required to reach multiple kV DC link voltages. Multi-level converters require more complex topologies and a larger number of switches, diodes, and/or capacitors. Due to the very high blocking voltages of SiC, it is now possible to build single level converters up to 24 kV. Single level SiC converters have the potential of dramatic cost savings over multi-level silicon-based converters as the device costs of SiC are reduced. Two modules are presented here designed for 15 kV/ 120 A and 24 kV / 30 A. These modules are designed to be compact, while meeting all creepage and clearance standards for their voltage ratings, operate at 200 °C, have a very low inductance, and fast switching speed.

Wide bandgap packaging for next generation power conversion systems

APEI, Inc. manufactures high performance, high temperature wide bandgap discrete packages, multi-chip power modules (MCPMs), and integrated systems for extreme environment applications. In this paper, APEI, Inc. presents two MCPMs, the HT-2000 and X-5, and two discrete packages, the X-6, and XHV-2, which were designed using advanced packaging materials and processes enabling high temperature operation coupled with high performance operation due to the superior characteristics of wide bandgap power switches. The key features of each of these packages will be discussed in this report.