Brandon Passmore

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 650 V/150 A enhancement mode GaN-based half-bridge power module for high frequency power conversion systems

Over the past decade, wide bandgap power devices have demonstrated superior electrical and thermal characteristics over Si-based devices at not only the die level but also when integrated into systems. In this paper, a high current 650 V GaN-based power module is presented for high frequency, high power conversion systems. The design and key features of the GaN-based power module are discussed. Both the thermal and electrical characteristics of the GaN-based power module were modeled to estimate the junction-to-case thermal resistance, power loop inductance, and power loop resistance. In addition, the on-state curves, on-resistance, and drain leakage were measured as a function of temperature. The dynamic characteristics were measured to evaluate the fidelity of the transient voltage and current waveforms, switching speeds, and estimate the switching energy losses.

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.

Design of a 250 kW, 1200 V SiC MOSFET-based three-phase inverter by considering a subsystem level design optimization approach

Silicon carbide (SiC) power semiconductor technology has successfully penetrated several silicon (Si) application markets and is gaining momentum due to higher voltage withstand capability, higher switching capabilities (i.e., 100s of kHz), and ability to withstand higher operating temperatures (i.e., more than 200°C). When properly applied, SiC MOSFETs can switch in nanoseconds making this a promising candidate for high-power, high-temperature, highspeed, and high-efficiency power converter applications. In fact, many consider the SiC MOSFET as the most “ideal” power semiconductor switch developed to date. To maximize the benefit of this fast switching power device, it is necessary to exercise extraordinary care when designing the power converters subsystems. In this paper, an approach based on a subsystem optimization approach is presented wherein the power module, the DC and AC bus structures, the DC link capacitor bank, and the gate driver controls are discussed for a 16 kg, 250 kW all-SiC three-phase inverter.

A compact 110 kVA, 140°C ambient, 105°C liquid cooled, all-SiC inverter for electric vehicle traction drives

Wide bandgap materials are having a transformational impact on the electrical, thermal, and mechanical performance of military, industrial, and commercial power electronic systems where silicon (Si) power semiconductors are the present material technology of choice. This paper reports on the design, analysis, and experimental verification of a compact allsilicon carbide (SiC)-based inverter to meet the inhospitable environmental demands of hybrid, plug-in hybrid, extended-range electrified vehicles, and fuel cell vehicle architectures. The compact 4.8 L, 6.6 kg inverter achieves a volumetric and gravimetric power density of 23.1 kVA/L and 16.8 kVA/kg, respectively. Three 1200 V, 3.6 mΩ, half-bridge power modules, each containing seven 25 mΩ SiC MOSFETs and six 50 A Schottky barrier diodes (SBDs) per switch position, comprise the power stage. Significant improvement in conduction, switching, and reverse-recovery losses allowed this SiC MOSFET-based inverter to achieve 96.3% average efficiency and 98.9% average peak efficiency over all experiments. This is superior to Si IGBT-based inverters throughout the entire range of torques, speeds, and bus voltages — and especially at light load operating points typical of electric vehicles. Dynamometer experiments used a 20 kHz switching frequency, double-update space-vector modulation, thermal controls for ambient and coolant temperatures, custom data acquisition, and a commercial three-phase power meter to collect performance data over 500 to 6000 RPM, 5 to 180 N-m, four bus voltages, and six thermal cases.

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%.

A review of SiC power module packaging technologies: Attaches, interconnections, and advanced heat transfer

This paper reviews the challenges and recent advances in packaging that can be utilized for silicon carbide (SiC) power devices. It focuses on the recent progress in three primary areas consisting of: 1) attaches, 2) die interconnections, and 3) advanced heat transfer techniques. Various technologies in each of these areas are discussed and evaluated to define the advantages and disadvantages of each.

Direct liquid cooling of high performance Silicon Carbide (SiC) power modules

Silicon Carbide (SiC) wide band gap power devices are capable of operating at extremely high current densities and switching frequencies. Systems embracing these benefits can achieve a substantial increase in power density. However, cooling becomes exponentially more difficult as the size of the modules lessens. Direct cooling of the power electronic modules, in which the liquid coolant flows over the surfaces of the base plate, is a highly effective approach to improve the thermal performance of a conversion system. Notably, it allows for a reduction of layers in the thermal stack-up and completely eliminates the need for a thermal interface material (TIM). In this work, Wolfspeed has taken the commercial CAS325M12HM2 SiC power module, which was specifically designed to take advantage of wide band gap power semiconductors, and developed a prototype variant to enable direct liquid cooling of the base plate. High surface area pin fins are formed in a concentrated density directly on the base plate, providing a quality means of heat removal as close to the semiconductor devices as possible. High thermal conductivity materials and attaches, including silver sintering paste and film, were utilized to achieve an optimized heat transfer path. The discussion presents the design, analysis, and testing of this direct cooled module. It focuses on various physical factors influencing the thermal performance and a comparison between different direct structural configurations and power levels.

System-Level Packaging of Wide Bandgap Inverters for Electric Traction Drive Vehicles

In this paper, we describe the system-level packaging of a 30 kW continuous, 55 kW peak, traction inverter to showcase the electro-thermal-mechanical performance enhancements of silicon carbide (SiC), a wide bandgap (WBG) semiconductor, over silicon. Higher efficiency, larger gravimetric and volumetric power densities, and smaller thermal management system requirements may be achieved through higher operating junction temperatures afforded by SiC versus silicon power devices. By applying advanced system-level packaging techniques, high-temperature control circuitry, utilizing 105°C-rated capacitors, and reducing the number of system interconnects and attaches to enable higher system reliability, a substantial cost reduction from the die level to the system level can be demonstrated by completely eliminating an electric vehicle’s secondary low-temperature cooling loop. The endgame is to reduce the traction inverter size (≥ 13.4 kW [peak]/L), weight (≥ 14.1 kW [peak]/kg), and cost (≤