The EU has set an ambitious goal of reducing its overall greenhouse gas emissions by at least 80% by 2050. To achieve this goal, the contribution of the automotive industry will be very important. Although the average fuel economy (CAFE) standard of American enterprises is likely to be reviewed by Trump government, it plays an important role in improving the environmental protection of vehicles. If these standards remain unchanged, automakers will need to significantly improve fuel economy in all areas, with an average of 49 mpg per gallon expected by 2022.
If all these objectives are to be achieved, it will become essential to have a larger market share for electric vehicles (EV) and hybrid electric vehicles (HEV). According to Bloomberg New Energy Finance, electric vehicles will account for 35% (equivalent to 41 million) of global annual vehicle shipments by 2040. However, there is still a huge gap between these and what we see in today's market. With the exception of Norway (which now sells more than 20% of its cars as plug-in electric vehicles) and the Netherlands (which has nearly 10% market share), including Germany, the United States, China, France, the United Kingdom and Japan, the market share of electric vehicles is less than 1.5%.
In order to realize the significant transformation from internal combustion engine to more environmentally friendly HEV/EV vehicle, the core challenge that must be overcome is the very important power electronics technology. Consumers have to pay a reluctant initial investment when buying a car, which comes mainly from the cost of power inverters and energy storage components. Other major challenges include the distance a car can travel once it is charged and the length of the charging process. Similarly, these problems arise from the power electrons used.
Improving the efficiency level of power supply will help to make the inverter smaller, so it also has a higher performance-price ratio. This will also make them lighter, enabling vehicles to travel longer distances. At the same time, the emergence of broadband gap technologies such as GaN or SiC provides a technical way to avoid inherent power loss in silicon devices. GaN and SiC have higher electron mobility and lower RDS [ON] parameters than silicon devices. They also support high switching speed, higher breakdown voltage and higher thermal conductivity (especially SiC). Improving power conversion efficiency can bring many benefits to thermal management. For example, the problem of heat dissipation has become less worrying, resulting in lower inventory costs, less space and still high reliability.
GaN Systems'GS6650x series GaN transistors are optimized for high-voltage systems (up to 650V) in HEV/EV designs. Because of the company's proprietary Island Technology, bus bars are no longer needed, thus saving space. These transistors can also get current vertically from the chip, which can reduce inductance loss and achieve higher quality factor (FoM) values. This in turn helps to reduce the trade-off between saturated voltage and switching loss. The GANPX package is used to ensure that inductance and thermal resistance are effectively suppressed despite its compact shape.
Similarly, the Panasonic's X-GaN series of enhanced mode GaN power transistors have higher breakdown voltage (more than 600V), and only need the smallest PCB space and a very limited number of additional passive components.
Figure 1: GaN System GS6650x series GaN transistors for HEV/EV design.
Figure 2: Shape comparison of traditional MOS silicon transistors and Panasonic's X-GaN''devices.
GeneSiC combines advanced insulated gate bipolar transistors (IGBT) with low loss and SiC diodes in its GA100SIC series products. By replacing traditional silicon continuous current diodes (freewheeling diodes) with SiC-based Schottky rectifiers, the switching performance has been greatly improved.
Here are some examples of product innovation in the fields of silicon carbide and gallium nitride for automotive engineers to refer to when implementing the next generation of power inverter technology.
Because power discrete devices using broadband gap compounds can support higher voltage and faster switching speed, they are destined to be the basis of future HEV/EV power systems. The huge potential of these new semiconductor materials is just beginning to be recognized.