Jeffrey Joseph Nasadoski

10 kV, 120 A SiC half H-bridge power MOSFET modules suitable for high frequency, medium voltage applications

The majority carrier domain of power semiconductor devices has been extended to 10 kV with the advent of SiC MOSFETs and Schottky diodes. The devices exhibit excellent static and dynamic properties with encouraging preliminary reliability. Twenty-four MOSFETs and twelve Schottky diodes have been assembled in a 10 kV half H-bridge power module to increase the current handling capability to 120 A per switch without compromising the die-level characteristics. For the first time, a custom designed system (13.8 kV to 465/√3 V solid state power substation) has been successfully demonstrated with these state of the art SiC modules up to 855 kVA operation and 97% efficiency. Soft-switching at 20 kHz, the SiC enabled SSPS represents a 70% reduction in weight and 50% reduction in size when compared to a 60 Hz conventional, analog transformer.

Recent advances in silicon carbide MOSFET power devices

Emerging silicon carbide (SiC) MOSFET power devices promise to displace silicon IGBTs from the majority of challenging power electronics applications by enabling superior efficiency and power density, as well as capability to operate at higher temperatures. This paper reports on the recent progress in development of 1200V SiC power MOSFETs. Two different chip sizes were fabricated and tested: 15A (0.225cm×0.45cm) and 30A (0.45cm×0.45cm) devices. First, the 30A MOSFETs were packaged as discrete components and static and switching measurements were performed. The device blocking voltage was 1200V and typical on-resistance was less than 50 mΩ with gate-source voltages of 0V and 20V, respectively. The total switching losses were 0.6 mJ, over five times lower than the competing devices. Next, a buck converter was built for evaluating long-term stability of the MOSFETs and typical switching waveforms are presented. Finally, the 15A MOSFETs were used for fabrication of 150A all-SiC modules. The module on-resistance values were in the range of 10 mQ, resulting in the best-in-class on-state voltage values of 1.5V at nominal current. The module switching losses were 2.3 mJ during turn-on and 1 mJ during turn-off, also significantly better than competing designs. The results validate performance advantages of the SiC MOSFETs, moving them a step closer to power electronics applications.

Direct comparison of silicon and silicon carbide power transistors in high-frequency hard-switched applications

RECENT progress in wide bandgap power (WBG) switches shows great potential. Silicon carbide (SiC) is a promising material for power devices with breakdown voltages of several hundred volts up to 10 kV. SiC Schottky power diodes have achieved widespread commercial acceptance. Recently, much progress has been made on active SiC switches, including JFETs, thyristors, BJTs, IGBTs, and MOSFETs. Many a great promise has been made, and wondrous claims abound, but the question remains: will they live up to the hype? We explore this question for the class of high-frequency, hard-switched converters with input voltages of up to 600 VDC and power throughputs in the kilowatt range. Experimental evidence shows that both superior efficiency and higher power density may be obtained via the use of SiC MOSFETs. A direct comparison is made using silicon power devices (IGBTs and MOSFETs) and SiC MOSFETs in a 200 kHz, 6 kW, 600 V hard-switched converter. The losses are measured and conduction and switching losses of the active devices are estimated. Total losses can be reduced by a factor of 2–5 by substitution of SiC MOSFETs for Si active power devices.

Overview of 1.2kV – 2.2kV SiC MOSFETs targeted for industrial power conversion applications

This paper presents the latest 1.2kV-2.2kV SiC MOSFETs designed to maximize SiC device benefits for high-power, medium voltage power conversion applications. 1.2kV, 1.7kV and 2.2kV devices with die size of 4.5mm × 4.5mm were fabricated, exhibiting room temperature on-resistances of 34mOhm, 39mOhm and 41mOhm, respectively. The ability to safely withstand single-pulse avalanche energies of over 17J/cm2 is demonstrated. Next, the 1.7kV SiC MOSFETs were used to fabricate half-bridge power modules. The module typical onresistance was 7mOhm at Tj=25°C and 11mOhm at 150°C. The module exhibits 9mJ turn-on and 14mJ turn-off losses at Vds=900V, Id=400A. Validation of GEs SiC MOSFET performance advantages was done through continuous buck-boost operation with three 1.7kV modules per phase leg exhibiting 99.4% efficiency. Device ruggedness and tolerance to terrestrial cosmic radiation was evaluated. Experimental results show that higher voltage devices (2.2kV and 3.3kV) are more susceptible to cosmic radiation, requiring up to 45% derating in order to achieve module failure rate of 100 FIT, while 1.2kV MOSFETs require only 25% derating to deliver similar FIT rate. Finally, the feasibility of medium voltage power conversion based on series connected 1.2kV SiC MOSFETs with body diode is demonstrated.

A 900W, 300V to 50V Dc-dc Power Converter with a 30MHz Switching Frequency

Designers of power conversion circuits are under relentless pressure to increase power density while maintaining high efficiency. A primary path to higher power density is the use of increased switching frequency. In this paper it is argued that the use of switching frequencies in the VHF band (30MHz-300MHz) are a viable path to the achievement of substantive gains in power density. Evidence for this viewpoint is presented in the form of an unregulated 900W prototype dc-dc converter with a 30MHz switching frequency, an input voltage range of 270VDC to 330VDC, and an output voltage of 50VDC. This converter uses a quad module architecture with series input and parallel output to provide acceptable efficiency with the specified input voltage range. This converter operates with peak output power of 1kW at 330VDC input, and has an efficiency of ≫ 78% under nominal conditions, with maximum efficiency near 80%.

DC and Transient Performance of 4H-SiC Double-Implant MOSFETs

SiC vertical MOSFETs were fabricated and characterized, achieving blocking voltages around 1 kV and specific on-resistances as low as RSP,ON=8.3 mOmegamiddotcm2. DC and transient characteristics are shown. Room and elevated temperature (up to 200degC) 600 V/5 A inductive switching performance of the SiC MOSFETs are shown with turn-on and turn-off transients of approximately 20-40 ns.

Static and dynamic characterization of 6.5kV, 100A SiC Bipolar PiN Diode modules

High voltage and high current SiC bipolar diode modules are fabricated and characterized under static and dynamic conditions. The modules are built using 6×6mm2 SiC chips that are fabricated on 3″ SiC substrates. Individual chips were also packaged in an ISOPLUS™ package and used to perform switching tests on the diodes. The modules have been fully characterized under static and dynamic conditions. These modules are targeted for high voltage, high frequency applications, as well as antiparallel diodes for 6.5kV IGBTs, IGCTs, and IEGTs.