High Current SiC Cascodes for Electric Drive Vehicle Power Electronics

In 2014, approximately ~120,000 plug-in electric vehicles (PEV’s) were sold in the US alone, representing a 23% increase from 2013 and a 128% increase from 2012 and nearly 1/3 of the PEV’s sold worldwide, making the US the largest market for PEV and HEV adoption. It is expected that by 2023, there will be ~3.2 million PEV’s on the road in the U.S. alone. The EV Everywhere initiative has set the goal to make electric vehicles as affordable as gasoline vehicles by 2022. To meet the goals of the EV Everywhere initiative, the primary efforts lie in reducing costs for the batteries, PM motor and electric drive train while simultaneously reducing weight. Increasing the drive train conversion efficiency has a significant impact as it extends battery life, vehicle range and allows for a reduction of heavy cooling components through the reduction of heat generating losses. Therefore much attention is placed on increasing the efficiency of the traction power inverter that drives the electric motor. It is well documented that inverter efficiency and power density can be increased while simultaneously reducing weight through the use of Silicon Carbide (SiC) wide bandgap semiconductors. For example, demonstrations of inverters utilizing SiC-JFETs and SiC-MOSFETs are emerging, where the efficiencies are reaching >99% with 10X increased power densities. However, today’s electric vehicle motor drive applications require high current (200-400A) power modules. SiC devices have been limited to lower current (<50A) due to the material defects, lower yields and higher costs associated with large area devices. For the electric vehicle traction inverters, it is of great interest to push up the SiC device current to 100-200A per device to make full use of the SiC system. Material defect densities have dropped dramatically in recent years as the commercial acceptance of the SiC Schottky diode have driven higher volume and more state-of-the-art semiconductor fabrication. To address topic 14b, USCi proposes in Phase I to fabricate 100A 650V SiC Cascode Switches on 6” diameter wafers. The large area high current cascodes will be packaged in a stack format resulting in a very high power density potential. In Phase II, the cascodes will be packaged to assess performance with advanced high density modules. When integrated, the SiC cascodes will increase the efficiency of electric motor power conversion from the battery to the drive train. In Phase II, the goal will be to qualify the high current cascodes on the system level for automotive applications. Key Words: Silicon Carbide, Cascodes, Electric Vehicle, Inverters, High Current