In power electronics, silicon dominates the past and the present. But is silicon carbide (SiC) the semiconductor material of the future for power applications?
There’s a long way to go for SiC to overtake silicon. According to Yole Group, the market for SiC in power electronics will grow to reach US$10 billion by 2029, representing 28.6% of the worldwide market.1 That’s substantial, but still not sitting in first place, and of course silicon is still dominant in the market for logic and memory.
Silicon carbide is a wide bandgap (WBG) semiconductor, and this larger bandgap gives it some major advantages over silicon. Perhaps the most important is improved efficiency – while SiC can also operate at higher temperatures and voltages than silicon, and enable greater power density. Silicon IGBTs are still a good option for many power applications up to around 1200V, but for higher efficiency as a result of higher frequency operation, SiC is taking over.
In this article, we look at the applications using SiC devices, such as MOSFETs and Schottky diodes, and review why SiC is a good fit.
Applications
Figure 1: GaN, silicon and SiC compared(‘FOM’ means ‘figure of merit’ – applications in this area may suit multiple semiconductor technologies, and specific comparisons are needed to find the best choice in each case). Source: https://my.avnet.com/silica/resources/article/power-trends-si-sic-gan/)
(note: the x-axis shows voltage, while the y-axis shows switching frequency)
While we have highlighted some important application areas, there is also a wide variety of other use cases where SiC is finding a niche – such as industrial uninterruptible power supply (UPS) and motor drive applications.
In general, SiC is ideal for applications involving higher switching frequencies and greater voltages, compared to use cases that suit gallium nitride (GaN) or silicon (see Figure 1), while high temperature operation may also be a factor. Beyond technical factors, silicon devices are typically less expensive, giving them the edge in cost-sensitive applications.
Automotive and electric vehicles
Automotive is a large and growing market for SiC devices, and particularly the booming electric vehicle (EV) sector.
The efficiency of SiC is critical for EV applications, as well as its ability to perform well at high temperatures and high voltages.
The most important component in an EV’s power train is the traction inverter, which handles the conversion of DC power (supplied by the car’s battery) into the AC power that the electric motor needs. While silicon has been used previously, the higher efficiency of SiC inverters makes them attractive, helping to increase range without requiring a larger, more expensive battery.
SiC’s ability to operate at higher temperatures and better thermal conductivity could enable more compact traction inverters with higher power density, saving valuable space and weight in a vehicle. SiC can also operate at higher voltages than silicon, giving new options for designers.
The higher power density achievable with SiC enables more compact designs for the onboard charger (OBC), which converts AC power from the grid into DC, as well as for the car’s fast charging system for use with rapid, high-voltage DC chargers.
Technology
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With the ongoing shift to renewable energy and the electrification of transport and industry, the demand for higher power and greater energy efficiency in electronics is increasing. Wide bandgap technologies including SiC and GaN bring many advantages.
WBG OVERVIEWEV charging
As well as the vehicles themselves, the electrification of our cars depends on a reliable, effective network of chargers – ranging from plug-in chargers for home use, all the way to DC fast charging systems that can deliver a substantial charge in just a few minutes. Unsurprisingly, the high efficiency of SiC-based components makes them attractive in these applications.
There is a shift in the EV industry underway from existing 400 V designs, to a higher voltage 800 V bus architecture. To make this possible, the high voltage capabilities of SiC mean it is the key enabling technology.
Moving to this higher voltage means that the current can be lower while still delivering the same power, or charging speed can be increased with increased power – without requiring additional cooling. If the lower current option is chosen, then the charging cables can be smaller, thus reducing their cost as well as saving weight and space.
Data centres
When you store your photos in the cloud, stream a video or ask your smart speaker a question, you’re using a data centre. With the rapid development of AI in our world, the demand for data centres and the networks that connect them is growing fast – and that means more power is needed.
It’s not just about providing the electricity needed to run the servers, storage, back-up systems and other computer components. One of the biggest power users in data centres is the cooling system, which removes the heat dissipated by all the hardware.
To minimise waste heat, and to keep electricity costs down, the power systems in a data centre must be highly efficient – SiC inverters are the ideal solution. There’s also a need to make power systems as small as possible, so they can fit into restricted spaces, including directly in the server racks they are powering. Again, SiC fits the bill, enabling high power density and compact designs.
SiC is being used to power greener energyRenewable and green energy
Renewables is another important market for SiC, with its high efficiency making SiC devices attractive. The lower switching losses of SiC MOSFETs (including reduced turn-on, turn-off, and conduction losses) means lower operation losses than an equivalent silicon IGBT device.
In solar photovoltaic (PV) applications, inverters are required to create a suitable AC voltage. While small or home systems may use GaN inverters, larger installations will typically use SiC-based devices.
Another use for SiC is in large-scale energy storage systems (ESSs), where their excellent efficiency can enable lower cooling costs. SiC-based components’ high efficiency and power density also means they are finding uses in other energy infrastructure applications, including heat pumps and microgrids.
Design considerations
Designing with SiC devices brings up some new challenges, and requires careful consideration – SiC is not just a plug-in replacement for existing silicon-based components.
For example, gate drivers for SiC devices are different from the equivalents used with silicon components. A dedicated driver can be best, with digital drivers providing more precise control, for example, to minimise conduction losses and avoid unintended turn-on.
The high power density of SiC-based systems creates new thermal challenges that must be considered, particularly because thermal stress is a significant factor impacting reliability. The high switching frequencies also mean that noise and EMI will be an issue, and suitable filtering is needed.
Choosing wisely
Although there are design challenges to consider, the benefits of moving to SiC can be substantial across a broad range of applications.
Help is at hand. Talk to Avnet Silica’s FAEs and power engineers for expert information and guidance, empowering you to make the right choices for your next power system design.
Reference
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