The roadmap for increasing the energy density begins with minimizing the dynamic losses of conduction. Even more than silicon carbide, gallium nitride can significantly reduce dynamic loss and thus can reduce overall loss. So this is one way to get to high energy density in the future. The second parameter is the thickness of the total inverter stack; It is important to design a flat and thin reflective casing. The third possibility is to increase the temperature of the process. The high-temperature roadmap calls for the device to run at 175°C, and even more so, at 200°C in the future. For the first aspect, reducing losses, we need to move to power devices based on silicon carbide and gallium nitride. For electric vehicle applications, we will be talking about devices that range from 600 to 1200 volts. Here, silicon carbide and gallium nitride devices can outperform even bipolar devices such as IGBT, greatly reducing conduction losses and switching losses. This is true for several reasons. First, they are majority-bearer devices, which means that they do not have any minority storage effects. The lateral construction of GaN gives it a slight advantage over silicon carbide in terms of dynamic or shift losses. Compared with equivalent SiC (vertical device, inversion channel), the high mobility 2D electron gas channel allows the 600-V GaN device to have lower channel resistance and thus smaller wafer size, and the profile structure allows for lower capacitance. Considering the input capacitance impedance times, output capacitance, and reverse recovery characteristics, we see that 600-V GaN and SiC wide bandgap devices outperform the supercapacitive silicon equivalent. Ron x Ciss is an indicator of how fast you can drive your portal ring. SiC and GaN produce a faster gate loop, which reduces switching loss, but GaN is significantly better than SiC, partly because of the lateral structure and partly because the design base used is a sub-micron-deep CMOS. The second number of merit is rune x cos. This again is to reduce switching losses, because the capacitance will store the energy that will be dissipated when the devices are turned on. The third is the Reverse Retrieval (Ron × Qrr) property; Here, silicon carbide is much better than silicon and GaN is slightly better than SiC. So together, we can see that the reverse recovery in GaN and SiC is essentially eliminated. At 20 kHz, which is typical for an EV inverter, the switching loss is negligible, so conduction loss will begin to dominate the overall losses. I2R losses can be proportionally reduced by using more and more devices in parallel as long as there is enough space to put the device in your AV inverter, which is of course directly related to the power density. Of course, one important factor for increasing power density is the encapsulation form factor, or device thickness. Here again, we believe that GaN has an advantage over silicon carbide. Written by Alex Qiu Hwang, Professor at the University of Texas at Austin, Register for the roadmap to the Next Generation EV & AV Virtual Conference to view this and other on-demand presentations. Cover Image: Pixabay Please visit the e-book for the full article.