SiC transistors industry
Bipolar SiC transistors enhance electrical power conversion
Today’s switch-mode power converters restrict the efficiency of solar systems and hybrid electric vehicles. One way to lift this barrier, while cutting the bill of materials at the system level, is to replace the silicon transistors with SiC bipolar equivalents that can deliver currents of up to 50A, argues Fairchild’s Anders Lindgren.
T
ransistors built from SiC are set to play a key role in improving the efficiency, while cutting size and
weight, of various electrical products serving a diverse range of applications. These wide bandgap semiconductor devices will probably first make an impact in the renewable energy sector, increasing the efficiency of solar inverters and slashing their bill of materials, thanks to a reduction in heat sink requirements and size of the filter inductances.
SiC transistors also promise to improve the driving range of hybrid electric vehicles, by cutting the size and weight of the hybrid inverter systems. And these robust transistors are also attracting the attention of engineers in the geothermal, oil and gas industries, who are searching for devices that can operate at really high temperatures. SiC transistors will also enable down-hole tools to operate at even further depths, allowing for a greater and more widespread use of geothermal energy.
At TranSiC, now part of Fairchild Semiconductor, we are pioneering the development of bipolar SiC technology that can serve this broad range of applications. Our efforts account for the differing requirements of all these applications that look to exploit different properties of SiC. Industrial applications, such as PV inverters, can mainly benefit from the high efficiency of SiC transistors, and their ability to operate at very high switching frequencies. In comparison, for down-hole applications, the higher operational temperatures of a SiC bipolar transistors is its primary asset. However, efficiency is an important property here as well, since losses contribute to additional device heating.
Figure 1 I-V-forward characteristics of the SiC BJT compared to the silicon IGBT. The BJT’s collector current, IC
the collector-emitter voltage at a range of base currents, IB
, is plotted as a function of , ranging
from 250 mA to 1 A. The dotted red line represents the same parameters for the IGBT
To cater for these differences, we have embarked on a two-pronged product development program. One of the directions that we have taken services the need for high efficiency and low cost within the industrial market, with components packaged in plastic TO-247 packages for use up to 175 °C.
The other approach focuses on high temperature and has yielded devices in TO-258 metal packages operating at junction temperatures of up to 250 °C. All of these applications are based on switch-mode power conversion.
June 2011
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