18 January 2012

AOS and SemiSouth demo 1200V Si/SiC stack-cascode MOSFETs

Power semiconductor designer Alpha and Omega Semiconductor Ltd (AOS) of Sunnyvale, CA, USA and SemiSouth Laboratories Inc of Starkville, MS, USA (which designs and manufactures silicon carbide devices for high-power, high-efficiency, harsh-environment power management and conversion applications) have jointly demonstrated UniSiC, a 1200V, 90mΩ MOSFET in a TO262 package, to meet the growing need for energy-efficient switching devices for high-performance power conversion applications in the alternative energy, industrial and consumer segments. The firms claim exceptional figures-of-merit and reduction in form factor for the 1200V MOSFET device.

AOS says that it continues to execute its strategy to be a full-service power solution provider by extending its portfolio of AlphaMOS MOSFETs and AlphaIGBT silicon devices with the new 1200V MOSFET.

Figure 1: Die sizes of a 1200V IGBT with co-packaged diode, a competitor 1200V SiC MOSFET, and AOS’ UniSiC stack-cascode device.

The UniSiC device is formed by stacking a low-voltage silicon MOSFET atop a normally-on SiC JFET (provided by SemiSouth). The low-voltage MOSFET is specially engineered to allow optimal operation of the composite device with clean switching, and low Rdson and gate charge. It is intended to provide great ease of use (working with standard drive circuitry) and to drastically improve circuit efficiencies over the whole range of load current.

The UniSiC MOSFET provides what is claimed to be unprecedentedly low Rdson and gate charge Qg, an excellent body diode with virtually no stored charge, and a low diode forward voltage drop. The device may be used similarly to a conventional MOSFET or IGBT, with standard gate drives, and is engineered so it can be switched over a wide speed range (as fast as a superjunction MOSFET or as slow as an IGBT). The device has what are claimed to be far superior characteristics compared to existing IGBTs, silicon power MOSFETs or even the best competitive SiC 1200V MOSFET. In addition, the small die size shows the potential for future miniaturization of power circuits, given how much it cuts conduction and switching losses.

“Using the superb characteristics of SiC JFETs for high-voltage applications, and solving the switching problems that have plagued cascode devices in the past, AOS is in a position to offer the power electronics community a dream switch,” claims Dr Anup Bhalla, VP of High-Voltage Discretes at AOS. “The devices can be used like conventional discrete IGBTs and FETs using the same gate drives, allowing the user to realize huge efficiency gains without too much re-engineering,” he adds.

“First released in 2008, we have seen our JFET products gain rapid adoption in the market, and this first-ever stack-cascode demonstration from AOS really takes the performance and ease of use to the next level,” says SemiSouth’s president & chief technology officer Dr Jeff Casady.

Tags: SemiSouth SiC SiC MOSFETs

Visit: www.aosmd.com

Visit: www.semisouth.com

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