Fuel vehicles around the world are transforming to electric vehicles and smart driving new energy. By 2030, the total global market for electric vehicle and hybrid vehicle batteries is expected to grow to nearly $1.6 billion. The rapid development of this field must be supported by the optimization of vehicle design, and vehicle design must be prepared to meet this epoch-making change. Among them, SiC and GaN have played a leading role in helping electric vehicles and charging infrastructure extend driving range and shorten charging time.

The power of silicon carbide (SiC) in automotive applications

SiC is currently the most mature wide bandgap (WBG) power semiconductor technology. In recent years, SiC has proven to be a powerful ally for electric vehicles and plug-in hybrid vehicles. With its excellent thermal and electrical performance, SiC has become an enabling technology for electric vehicles and plug-in hybrid vehicles. One of the most obvious applications is power modules for DC/DC power converters and traction inverters, where the thermal resistance of SiC can be converted into more efficient thermal management. The direct result of all this is improved electric vehicle range and longer battery life.

In addition, the use of SiC inverters helps reduce switching losses, thereby improving the overall efficiency of the traction system. This is particularly important for electric vehicles, where every percentage point increase in efficiency translates directly into increased range and reduced energy consumption.

SiC’s properties, such as wide bandgap, also enable it to operate at higher temperatures, which is critical in automotive environments where thermal management is always a challenge. These properties help improve system stability and reliability, ensuring stable performance even under extreme driving conditions.

SiC also has excellent thermal properties and can conduct large amounts of thermal energy. SiC has led the way in wide bandgap technology into the electric vehicle space, replacing the previous silicon MOSFET or IGBT in traction inverters. SiC MOSFETs are known for their superior conductivity and switching performance. Leveraging SiC’s favorable properties, SiC MOSFETs have almost half the die area of ​​an IGBT and combine the following desirable characteristics for a power switch:

High voltage

Low resistance RDS(ON)

High switching speed

Low switching losses

SiC MOSFETs enable automotive system designers to increase efficiency; reduce heat sink size and cost; increase switching frequency to reduce magnetic component size; and reduce design cost, size, and weight. The use of SiC in electric vehicles in particular ensures higher driving range, smaller battery size and faster charging.

Compared to silicon IGBTs, SiC has higher operating temperatures and switching speeds, while also having a higher breakdown voltage at the same device size, which results in higher robustness and power density. These properties are particularly suitable for inverter modules in the automotive industry's powertrains, which must efficiently transfer large amounts of energy between the battery and the motor. Switching speed is one of the key parameters in the design of automotive systems and can influence their efficiency and performance. In the case of 800V battery systems and large battery capacities, SiC increases the efficiency of the inverter, which in turn increases operating time and reduces battery costs.

SiC also increases the efficiency and power density of on-board chargers (OBCs). The material enables a bidirectional flow of energy from the power source to the battery and vice versa. It also has a positive impact on battery management: it is possible to achieve a longer vehicle range with the same battery size or to use smaller and lighter batteries with the same range. In addition, the corresponding infrastructure can be charged faster thanks to SiC. Efficient vehicles are lighter in weight due to large battery capacity, low cooling intensity and optimized wiring. SiC system solutions help improve the overall efficiency of the vehicle, especially in the transmission, traction inverter and OBC. Finally, a significant advantage is that SiC devices can be installed with technologies designed and used for silicon.

Importance of Gallium Nitride (GaN) in Next Generation Vehicle Design

GaN is another material that is rapidly emerging in the automotive industry, especially in high-frequency power systems. GaN-based MOSFETs are well suited for applications such as DC/DC converters, battery chargers and battery management systems. Due to its high switching speed, GaN allows for the design of more compact and lighter converters, thereby reducing the overall weight of the vehicle and improving the energy efficiency of the entire system. This is particularly important in electric vehicles, where weight is a decisive design factor.

Compared to traditional materials, GaN's lower on-resistance helps reduce power losses in the powertrain and further improves the overall efficiency of the vehicle, which is key to ensuring that the energy stored in the battery is optimally utilized, thereby helping to maximize the range of electric vehicles. While SiC devices are most popular in high-voltage applications, GaN also offers valuable advantages when applied to platforms with lower battery voltages (up to about 400V).

Combined Applications of SiC and GaN in the Automotive Sector

It is well known that the automotive market is a dynamic sector with challenges in terms of weight and space. Not only must costs be carefully calculated, but voltages vary widely - from around 5V to over 100V for internal combustion engine vehicles and even higher for electric or hybrid vehicles. As the electric and hybrid vehicle markets grow and become more popular, efficient power conversion becomes even more important. As a result, designers are under constant pressure to integrate systems with increasing performance into smaller, lighter, and more efficient volumes in a cost-effective manner. GaN- and SiC-based power modules can help achieve many of the design goals of electric and hybrid vehicle systems. From the engine to the powertrain to the vehicle controls, from the driver's console to the infotainment system, every application in the car can benefit from improved efficiency and power density.

The combination of SiC and GaN in automotive systems opens up exciting prospects (see figure). The properties of both materials complement each other, allowing the design of efficient, reliable and compact electric traction systems. For example, integrating SiC and GaN into power modules not only maximizes the advantages of both materials, but also allows higher switching frequencies, improved energy efficiency, reduced power losses and optimized thermal management of components. This synergistic advantage is particularly important in electric vehicles, where high efficiency is increasingly important to overcome challenges related to range.

Figure: Rethinking automotive systems using WBG semiconductors. (Source: Texas Instruments)

The use of silicon carbide (SiC) and gallium nitride (GaN) to meet electric vehicle design requirements is now becoming a standard for next-generation automotive design to promote sustainable development. Aerodynamic lines or lighter materials are not enough to guarantee the efficiency of electric vehicles. To meet the requirements of efficiency and power density, power electronics designers must look to new technologies.

Advanced wide bandgap (WBG) semiconductor materials, especially GaN and SiC, represent an improvement over existing semiconductor technologies for MOSFETs and IGBTs. Fundamentally, the bandgap width corresponds to the energy required to excite an electron from the valence band of a material to the conduction band. In this sense, the bandgap width of WBG materials is much higher than that of silicon. Compared to silicon, WBG semiconductors enable devices to operate at much higher voltages, frequencies, and temperatures, with significantly lower switching and conduction losses. The conduction and switching characteristics of WBG materials are also about 10 times better than conventional silicon. These characteristics make WBG technology a natural fit for power electronics, especially for electric vehicles, as SiC and GaN devices can simultaneously offer smaller size, higher speed, and higher efficiency.

However, when evaluating the benefits of WBG devices, the complexity and higher cost of mass production must also be considered. While WBG devices may initially be more expensive, their cost will continue to decrease and ultimately save costs in the entire system in the future. For example, using SiC devices in an electric vehicle may increase initial costs by hundreds of euros, but overall costs can be saved due to lower battery costs, less space required, and simpler cooling solutions - such as using smaller heat sinks.

Technical Considerations for SiC and GaN Devices in Automotive Design

WBG power technology is integral to the success of electric and hybrid vehicles, overcoming some of the inherent limitations of electric vehicles and helping to accelerate the adoption of electric vehicles around the world. To meet the increasing efficiency and power density requirements of EV systems such as inverters and integrated chargers, automotive power electronics designers can take advantage of state-of-the-art WBG semiconductors such as SiC and GaN (Figure 1). As mentioned above, these products offer lower losses, higher switching frequencies, higher operating temperatures, robustness in harsh environments, and higher breakdown voltages compared to traditional silicon devices. SiC is a key technology designed specifically for a variety of EV applications such as traction inverters, onboard chargers (OBCs), and DC/DC power converters (Figure 2).

Figure 1: Relationship between WBG technology, operating frequency and system power. (Source: STMicroelectronics)

Figure 2: Application of SiC in electric vehicle systems. (Source: STMicroelectronics)

GaN and SiC can operate at higher temperatures with similar life expectancy or at similar temperatures to silicon devices with longer life. Today, power electronics system designers have a variety of design options to choose from based on the requirements of a specific application. Overall, using WBG materials allows for different design strategies and approaches to be chosen based on the goals of the end project. For example, we can decide to use the same switching frequency and increase the output power, or we can use the same switching frequency and reduce the amount of heat dissipation required in the system, saving overall component costs. Otherwise, designers can choose to increase the switching frequency while keeping the power losses of the switch the same. As you can see, there are many customizable options.

Inverter

The inverter is used to control the electric traction motor in an electric vehicle. It is a key component in the electric propulsion system and can benefit from WBG devices. The main function of the inverter is to convert DC voltage into a three-phase AC waveform to drive the car's motor, and then convert the AC voltage generated by regenerative braking into DC voltage to charge the battery. To drive the motor, the inverter converts the energy stored in the battery pack into AC, so the lower the losses in the conversion stage, the more efficient the system. Compared with silicon devices, SiC devices have higher conductivity and switching frequency. Therefore, SiC devices can reduce power losses because less energy is dissipated as heat. Therefore, the more efficient the SiC-based inverter is, the greater the range of the electric vehicle.

Today, many electric vehicle manufacturers are integrating SiC power modules in the main inverter. Using SiC to manufacture electric vehicle inverters can make them about 5 times smaller, about 3 times lighter, and reduce power losses by half compared to their silicon counterparts. For example, we can combine an OBC and a DC/DC converter in a smaller, lighter, and more efficient package than a similar design made with silicon devices.

OBC

Electric vehicle charging systems (also known as OBCs) need to convert electrical energy from AC (usually from the distribution network) to DC. With WBG devices, new circuits for charging electric vehicles can be realized. With a bandgap that is 2 to 3 times larger than silicon, WBG devices can withstand higher voltages and electric fields because more energy is required for electrons to move from the valence band to the conduction band. The breakdown voltage of WBG semiconductors is much higher, while the on-resistance is very small. This simplifies the design and improves the efficiency of the charging circuit. The low resistance RDS(ON) also reduces switching losses and power losses, thereby reducing the circuit size.

Another advantage of WBG devices is that they generate lower temperatures than silicon-based devices under the same operating conditions. In power circuits, SiC devices can withstand junction temperatures of even more than 200°C, while silicon devices can reach a maximum junction temperature of around 150°C. Therefore, using WBG devices in EV chargers enables higher switching speeds and better energy efficiency, resulting in more compact and easier to cool modules.

The OBC is installed at the factory. In a pure electric vehicle or plug-in hybrid vehicle, the OBC charges the battery from the home AC grid or a private/public charging station outlet. The OBC uses an AC/DC converter to convert 50/60Hz AC voltage (100 to 240V) to DC voltage to charge the high-voltage vehicle battery (usually around 400V DC voltage). It also adjusts the DC current level according to the battery requirements, provides electrical isolation and includes AC/DC power factor correction (PFC).

A typical EV OBC usually uses SiC diodes. The OBC needs to be as efficient and reliable as possible to ensure fast charging times, but it must also meet the design specifications for application space and weight. OBC designs using GaN technology can simplify cooling systems and reduce charging time and energy losses. Bidirectional OBCs are a key development direction for the adoption of electric vehicles in future sustainable smart grid infrastructure. Bidirectional OBCs allow electric vehicles to act as energy storage or other uses of energy to help manage supply and demand changes and help stabilize loads within the grid. GaN and SiC-based devices enable advanced bidirectional topologies and optimized power converter configurations.

Although GaN power devices appear to be slightly inferior to SiC at a commercial level, their market share is rapidly expanding due to their excellent efficiency performance. Similar to SiC devices, GaN devices offer lower switching losses, higher switching speeds, and higher power density, and can reduce overall system size, which is related to both weight and total cost. Typical silicon MOSFETs switch at low speeds, while GaN devices switch at high speeds to achieve the lowest possible losses. At this level of operation, system layout also has a significant impact on performance. Several manufacturers have developed automotive-grade SiC devices for OBC applications in electric and hybrid vehicles to reduce energy losses and achieve better electrical performance under load conditions.

DC/DC Power Converters

DC/DC converters power a variety of loads throughout the vehicle. When designing DC/DC converters for automotive applications, GaN devices can save power and significantly reduce circuit size and weight compared to ordinary silicon MOSFETs, while also achieving better thermal management performance and reliability. In high voltage and high power applications, these devices bring advantages to the automotive world, making modules smaller and lighter, thus helping to save space and improve energy efficiency. In addition, GaN ICs combined with 650/700V power transistors and optimized gate control can provide solutions to meet energy efficiency needs. Lower energy losses at high speeds enhance the potential for increasing switching frequencies in conversion circuits operating at 300-800kHz, allowing the use of smaller passive components, maximizing power density within compact module sizes.

Future Trends

WBG SiC and GaN technologies have played a leading role in helping electric vehicles and charging infrastructure extend driving range and reduce charging time. Improvements in both aspects are needed to convince more car buyers to choose electric vehicles that meet their typical usage needs. On the one hand, the growing market brings greater consumer pressure to adopt advanced electric vehicle technologies, including OBCs and DC/DC converters, to achieve better electrical performance with improved efficiency, power density and reliability, and reduced power losses. On the other hand, it also focuses on customer needs. In this sense, leading power electronic device manufacturers regularly release several generations of devices, and the performance of the next generation of devices will increase compared to the previous generation.

Future electric vehicles will unlock their full potential and meet growing market expectations by adopting a strategic combination of GaN and SiC semiconductors, each of which has advantages in different roles in the car. While SiC may still be the preferred technology at high voltages, electric vehicles can take advantage of the advantages of GaN devices at lower voltages to increase power density and efficiency.