Work on IGBT power switch rewarded with €1M in prize money

The Technology Academy Finland has awarded the 1-million-euro Millennium Technology Prize to Bantval Baliga, who made key contributions to commercializing the insulated gate bipolar transistor (IGBT). Currently working at North Carolina State University, but employed by GE when working on the IGBT in the 1980s, Baliga may be a contender for the person with the largest negative carbon footprint in the world, owing to the efficiency increases of electrical devices made possible by the IGBT.

The IGBT is a power semiconductor device that combines a bipolar power transistor with a MOS structure and an insulated gate terminal. It bears some resemblance to the more diode-like thyristor – in fact, suppressing thyristor action was a key element in creating a commercially viable IGBT. Baliga’s main contribution was to use carefully dosed electron irradiation to increase the device’s switching speed enough to make it useful.

IGBTs are used in a wide range of products when modestly high voltages need to be switched on and off quickly. GE needed them because the firm had a lot of products with induction motors, whose speeds were governed by the power-line frequency. “So when a machine required less oomph, there was no good way to slow it down. The usual workaround was to insert a physical barrier into the stream of air or water that was being pumped around,” a 2014 IEEE Spectrum article explains.

“Some GE engineers wanted to pursue a simple energy-saving idea: just drive the motor at the desired speed. But that required adding electronics to send power to a motor’s windings at variable frequencies, which wasn’t easy to do back then. The voltages were too high for metal-oxide-semiconductor field-effect transistors (MOSFETs) to work efficiently, and ordinary bipolar power transistors required bulky and expensive control and protection circuits.”

And so Baliga was put to work. GE started manufacturing IGBTs in the early 1980s. For this and subsequent contributions to the field of electrical engineering, Baliga was awarded the National Medal of Technology and Innovation in 2011 and the IEEE Medal of Honor in 2014.