TR2011-072

Charging Technology Enabler for Electric Vehicle



High DC voltage is key to ultra-fast charging in Electric Vehicle. This would imply the need for high efficient AC to DC converter and DC to DC converter. Current devices in these converters are silicon based with limited voltage and power handling. Wide bandgap semiconductors, however, are known for their high power density, high breakdown voltage, better thermal conductivity and smaller leakage current. Power devices designed from these semiconductors will have higher power efficiency with higher voltage, power, temperature limits and frequency switching speed. In addition, these devices may result in smaller heat sink and lower cost per watt and fanless equipment for both the charger and the converters in the electric vehicles. Current commercial HEVs/EVs use Si-based insulated gate bipolar transistors (IGBTs) remains the main technology for switching. Higher frequency and breakdown voltage of Si IGBT and MOS-FET have continuously been improved but are close to the limit of Si technology. Moreover, these devices normally come with large cooling systems. It is recognized that wide bandgap material has the potential to provide power devices with even higher frequency and breakdown voltage. The well- known wide bandgap materials are diamond, GaN and SiC, is shown in Table 1. At the moment the leading candidate is SiC. However, the cost is still on the high side. If GaN on sapphire or on Si can be successfully fabricated for high power and voltage, then they would be serious competitors to Si and SiC devices. Table 1 is a comparison of the physical properties of the various wide bandgap materials.