Climate has forced the industry to come up with alternative energy solutions. Innovative technologies such as solar and wind generation have displaced traditional fuel-based plants at an increasing rate, and the cost savings due to energy storage and harvesting methods have surpassed that of expensive gas “peaker” plants.
With government backing these relatively new technologies with policies and incentives, there are many opportunities for improvement and growth in public energy infrastructure and its associated grid structure.
Recent Advancements for Major Improvements
An older grid structure once consisted of one-way power delivery and limited energy generation such as fossil fuel, hydro power, and nuclear power plants. Recent advancements in renewable energy and harvesting have allowed this same grid to expand its electricity-generation sources (wind and solar) while creating flexible, two-way distribution meant for variable demands and storage options.
Speaking to solar energy specifically, installation typically requires inverters that convert DC voltage produced by the photovoltaic (PV) modules to an AC voltage, which is then transferred back to the grid. One of the most common ways to do this is by a string inverter scheme, whereby DC voltage coming from a string of solar panels is fed to a DC/DC boost stage, then a DC/AC inverter, and then connected to the grid.
Figure 1 shows a typical solar string inverter block diagram complete with gate driving, sensing, and processing. Power delivery for this configuration is generally done with IGBTs, high-voltage FETs, and, more commonly, power integrated modules (PIMs) that contain integrated IGBTs and diodes.
Another eco-conscious industry with similar high-power demands is electric vehicle (EV) charging. EVs have been increasing in popularity at an unprecedented rate; unfortunately, their charging stations have been lagging behind. The infrastructure for EV charging hasn’t quite reached gas-station–like availability with the fuel-up time that’s needed for consumers to feel comfortable about range of travel with minimal delays. DC fast-charging systems (as opposed to slower AC-based charging systems) operating at power levels of 350 kW have been shown to fully charge a vehicle in less than 10 minutes.
Figure 2 shows an example of a typical DC fast-charging block diagram containing the power path components and associated processing and peripherals.
It turns out that silicon carbide (SiC)-based components can provide a better power delivery solution for public energy infrastructure such as power grids and EV charging stations. Such a solution could, in turn, provide an improvement in terms of better conduction losses, leakage current, thermal management, surge capacity, and power density. What’s more, SiC-based technology allows for better overall efficiency, with increased reliability and an overall smaller footprint. Industry-leading companies like onsemi offer a family of SiC devices, so let’s explore these devices and dive into some of their applications.
SiC Technology — A Better Solution
Whether the application is solar, EV charging, or even server farms, it has been shown that SiC technology can outperform traditional silicon components and modules like silicon IGBTs/MOSFETs. But let’s start with a topic that jumps to the forefront of every designer’s mind: efficiency.
How does SiC give you increased efficiency? Many factors are involved, but primarily, the SiC benefits include higher operating temperatures and frequencies (as high as 1 MHz) at lower conduction losses (Vf), along with higher max voltage and current ratings (drain-source voltage up to 1,800 V and current capabilities of up to 100 A), which, in turn, allow for greater power efficiency and fewer cooling requirements when compared with silicon MOSFETs.
See Figure 3 for a diagram on how SiC technology provides some of the highest overall power capabilities for high-voltage and high-current applications.
Given that the on-resistance of these SiC devices is lower and power capability is so much higher, a SiC-based solution translates to greater operating efficiencies.
Figure 4 demonstrates how a SiC-based diode and MOSFET in tandem can help improve the power efficiency of a 5-kW boost converter by lowering conduction losses by as much as 73%.
The footprint for SiC-based circuits is generally much smaller due to the lower size requirements of associated inductors and capacitors. In fact, in some instances, it is as much as 75% smaller size due to the higher switching frequencies when compared with silicon-based circuits operating at the same power level. This is what provides the higher power density. And while SiC MOSFETs are typically 4× more expensive than traditional silicon MOSFETs, the overall system cost goes down because of these smaller inductors and capacitors.
When it comes to assembly and mechanical integration, it’s been shown that onsemi’s PIMs — such as the Q0/Q1/Q2PACK modules, which incorporate SiC components to help reduce overall component count — simplify the manufacturing process and lower development risk while allowing for a faster time to market.
Additionally, discrete, non-integrated solutions generally require more time with assembling thermal management components such as isolation pads and heatsinks while also introducing higher risk of bad thermal contact. PIM solutions provide a much easier assembly process, resulting in reduced assembly time/costs and higher reliability, while also allowing for a more compact end product due to power density benefits.
Figure 5 demonstrates a comparison of the assembly process for a discrete solution versus a PIM module.
Applying onsemi’s Power Solutions to Modern SiC Applications
onsemi’s PIM modules provide faster switching, higher power efficiency, and higher power density, these solutions also allow for lower system cost and size, but that’s not all. PIM modules aren’t always preferred over discrete components, and the power rating of the application along with the performance and cost considerations will generally drive the design decision. onsemi offers both discrete and PIM SiC solutions.
Figure 6 shows how one might choose between a discrete or PIM solution.
High-voltage auxiliary power supplies used for applications like UPS, motor driving, or a PV inverter typically have DC link voltages ranging from 300 VDC to 1,000 VDC, making it hard to incorporate lower-voltage auxiliary PSUs for displays, fans, or heaters. But SiC MOSFETs operate with a much higher blocking voltage and wider input voltage range, thereby allowing for more system flexibility and capabilities. In addition, higher frequencies and a lower on-resistance result in much smaller and higher-power solutions, as discussed in the SiC advantages section. But let’s see a direct comparison between an ESBC configured supply running at 75 kHz and a SiC-based supply running at 300 kHz. The SiC supply results in a lower size (about half), 20% more power output, and a significantly higher power efficiency.
See Figure 7 for the size and efficiency comparison.
onsemi offers a wide range of switching technologies and packaging types based on the application’s needs, as well as isolated drivers.
See Figure 8 for onsemi’s full portfolio of SiC devices.
Conclusion
SiC technology offers many benefits that improve power efficiencies and system reliability of the high-power hardware used for a fast-growing, state-funded public energy infrastructure industry, while lowering overall system cost and size.
Whether it’s a power grid utilizing renewable energy, an EV charging station, or other high-voltage/high-current applications, the SiC advantage should be considered. Explore onsemi’s industry-leading product portfolio on Arrow.com for a wide range of SiC devices suitable for all applications.