Appliance Design - February 2008 - (Page 38) Improved Induction COOKING TECHNOLOGY Fig. 1. Cross-sections of IGBT: a) TrenchStop-cell. b) Reverse conducting-cell. New IGBT concepts improve induction heating efficiencies. by peter stipan, oliver hellmund, and reinhard metz Peter Stipan is marketing and business development manager, Infineon Technologies, Wind Lake, Wis.; Oliver Hellmund is senior manager development, power devices, Infineon Technologies, Munich, Germany; and Reinhard Metz is chief technologist, CookTek, Chicago, Ill. 38 applianceDESIGN February 2008 he old saying that “a watched pot never boils” means that when impatiently waiting for something to happen, it seems to take forever – but that was before induction cooktops were invented. Now one can fill a pot of water, place it on an induction cooktop, turn on the energy and watch the water come to a boil within 30 seconds. Induction cooking uses electromagnetic energy to heat cookware made of magnetic material (steel, iron, nickel or various alloys). When the unit is turned on, the coils produce a high frequency alternating magnetic field that ultimately flows through the cookware. Molecules in the cookware move rapidly back and forth, causing the cookware to become hot and cook the food. The market for induction cooking increased rapidly in recent years, mainly in Europe for induction cooktops and Asia for rice cookers. The technology is now experiencing a growth trend in the Americas, with CookTek as a leading provider of induction cooktops for commercial applications, using Infineon Technologies Insulated Gate Bipolar Transistors (IGBTs). High efficiency is driving this market towards high-performance, induction cooking products. In fact, when using an induction cooktop, over 90 T percent of every dollar spent on energy goes right where it should go – into the pan. Gas delivers only 30 percent to the pan, and traditional electric about 65 percent. Induction circuits The most common circuit used today for induction cooking is the single-ended topology, which requires Infineon Technologies IGBTs with a blocking voltage of 1,200 V. The switching frequencies are in the range of about 25 kHz. It is obvious that only extremely low saturation voltage and low switching losses are suitable here in order to obtain a high efficiency. The Infineon TrenchStop™ technology is able to combine those two contradictory demands. This technology allows much thinner substrates and highly optimized doping schemes compared to a common Non-Punch-Through (NPT) technology. It is especially the fieldstop concept that reduces the saturation voltage effectively. The fieldstop principle is also applicable to thin wafer diodes. A further development on the basis of the TrenchStop technology is the integration of a reverse conducting diode into the IGBT structure according to the cross sections, as seen in Fig. 1. This technology is www.applianceDESIGN.com http://www.appliancedesign.com
For optimal viewing of this digital publication, please enable JavaScript and then refresh the page. If you would like to try to load the digital publication without using Flash Player detection, please click here.