2015 Tutorials

• Is GaN a Game Changing Device? Fred C. Lee
• 
  
  
  Fred C. Lee

  Abstract

  Recently a number of Gallium Nitride high electron mobility transistor (GaN HEMT) devices have been made available ranging from low voltage to high voltage and for both depletion-mode and enhancement-mode devices. Compared to silicon MOSFET, GaN has a much improved figure-of-merit and thus potentially capable of much higher operating frequencies, well into the megahertz range. Some of the high voltage (600V) GaN HEMT are based on normally-on device. GaN is connected in series with a low-voltage silicon MOSFET to emulate a conventional normally-off device. Although somewhat cumbersome, it does offer some interesting switching characteristics and can be quite effective if properly used. GaN devices are switching at a considerably higher speed. However, it is accompanied with high di/dt and dv/dt, thus, sensitive to parasitics. The high di/dt and dv/dt , if not contended, can result in high switching stresses, losses and noises.
  
  This presentation will cover the basic switching characteristics as well as merits and demerits of the currently available low voltage and high voltage GaN devices. A number of design examples, ranging from point-of-load to off-line converters, will be used to illustrate the potential impact of GaN devices when operated at a significantly higher switching frequencies. The achieved level of power density and efficiency is quite remarkable. This opens the door for a paradigm shift of the distributed power architecture, together with profound change of the current design and manufacturing practices.

• Is SiC a Game Changer? Dushan Boroyevich
• 
  
  
  Dushan Boroyevich

  Abstract

  Over the last two decades there has been much exhilaration about the anticipated transformation of power electronics that SiC devices would bring, which has been accompanied by tremendous efforts by governments and companies around the developed world to meet those expectations. The successful commercial use of SiC Schottky diodes over the last ten years has helped improve efficiency and reduce size of power converters in several applications, but only in the last couple of years, several SiC active switching devices became commercially available at reasonable cost and volume. CPES has been involved all along in characterizing the newest SiC devices and evaluating their potential to change existing applications and open completely new ones.
  
  This tutorial will review the state-of-the-art and summarize CPES experiences in evaluating the use of SiC devices in dc-dc, ac-dc (single- and three-phase) and dc-ac power converters, as well as in three-phase motor drives, for transportation and higher power applications, ranging from kilowatts to megawatts. It will be shown that SiC devices can provide tangible improvements to existing applications so that their adoption will be mostly determined by the converter cost tradeoffs. On the other hand, SiC opens two previously unachievable sorts of applications: power converters where power semiconductor devices operate at high-temperatures (> 200 C), and high-power conversion in megawatt range with switching frequencies in tens of kilohertz. In these new applications, the SiC adoption is mostly governed by system cost tradeoffs and will be fundamentally limited by the availability of other materials, passive devices, sensors, packaging, and system integration technologies that can operate at high-temperature, high-power and high-frequency.