Improving Energy Efficiency in Industrial Applications with Silicon Carbide
Industrial applications such as server power supplies, uninterruptible power supplies (UPS), and motor drives consume a significant portion of the world’s power. Thus, any increase in efficiency in industrial power supplies will substantially reduce a company’s operating costs. Combined with greater power density and better thermal performance, the demand for high-efficiency power supplies is increasing exponentially.
Several factors are driving this growth. The first is rising global energy awareness and increasingly urgency to use energy more wisely and efficiently. The second is the Internet of Things (IoT), which has resulted in the introduction of new technologies and services of all kinds into industrial applications. With Smart Industry initiatives such as Industry 4.0, machines, factories, and workplaces are becoming more intelligent and aware through the connection of devices to achieve greater autonomy, efficiency, reliability, and safety.
However, industrial automation, such as robotic and motorized production lines, comes with escalating use and cost of electricity to power these systems. To stay competitive, manufacturers need to be able to develop new operational practices that keep factory costs down. They also need to make the most of every square meter of floor space as equipment footprint directly impacts operational costs.
The impact of energy consumption also extends into the data center, which houses the servers that support industrial applications. Increasing data traffic through automation, artificial intelligence, and machine learning in turn increases the processing resources required to keep equipment operational. Thermal performance is also important, given that up to 20% of power consumed in a data center is used to keep the data centers cool.
The demand for greater efficiency, lower cost
As industrial equipment often runs 24/7, any improvement in efficiency quickly translates to real savings in terms of significantly reduced energy consumption. The most immediate way to address energy issues is to increase the energy efficiency of the systems that power these industrial systems. As John Palmour, one of the founders of Cree | Wolfspeed says, “The least expensive power is the power you don’t use.”
For this reason, there is tremendous pressure from industry, government, and manufacturers to develop more efficient power supplies. For example, standards like Energy Star and 80 Plus promote efficient energy use in power supply units (PSU). By meeting these standards, PSU OEMs can easily demonstrate the efficiency of their systems to a demanding marketplace.
Three characteristics – power density, thermal performance, and conversion efficiency – are among the biggest challenges for designers of power supplies. In addition, designers need to meet these challenges while minimizing overall system cost.
Traditional approaches to power supply design will continue to provide some improvement in these areas, but gains will be limited as developers have been focused on squeezing more from these systems for years. To achieve significant improvement, new approaches are required.
Silicon Carbide Delivers
Silicon carbide (SiC) is a wide bandgap semiconductor base material. It can be used as a bare die substrate, in discrete components like Schottky diodes and MOSFETs, as well as power modules.
Historically, silicon (Si) has been used as a semiconductor base for the majority of electronics applications. However, Si is an inefficient foundation for power supply systems when compared to SiC. SiC offers many advantages over Si (see Figure 1).
Silicon carbide (SiC) offers many advantages over traditional silicon (Si).
Source: Wolfspeed, A Cree Company
- SiC-based components have lower leakage currents compared to their Si counterparts. This is because electron-hole pairs generate slower in SiC than in Si, resulting in lower leakage current losses when a switch is off.
- SiC has a wide bandgap of 3 electronvolts (eV) and is able to withstand a voltage gradient over eight times greater than Si without undergoing avalanche breakdown. The increased critical breakdown strength of SiC enables components to withstand a higher voltage in the same package as Si. Because of this, SiC-based components like MOSFETs can be created at blocking voltages about 10X compared to Si. Thus, very high voltage, high power devices can be fabricated reliably, and designers can work within tighter margins to deliver higher performance. These devices can be placed very close together, allowing for greater packing density of components.
- Higher thermal conductivity results in more efficient heat transfer. Furthermore, a lower on-state resistance decreases conducting losses.
- SiC-based components are capable of higher switching frequencies. The higher switching frequency of SiC enables a peak efficiency of > 98.5%, making it possible for systems to meet the 80 Plus Titanium Standard (see Figure 2).
This graph shows of the efficiency of a 20kW SiC AC/DC convertor. As can be seen from these experimental results, the convertor is able to achieve a peak efficiency of > 98.5%, reaching 80 Plus Titanium standards.
Industrial applications that benefit from SiC
With these characteristics, SiC-based components enable power supplier designers to reach new levels of efficiency. The impact of SiC can be seen in a number of industrial applications:
Power factor correction (PFC)
PFC is a technique that can drastically reduce wasted power by increasing the power factor of a power supply. Without PFC, power supplies draw current in short, high magnitude pulses. With PFC, these pulses can be smoothed out to reduce the input root mean square (RMS) current and apparent input power. This effectively shapes the input current to maximize the power realized from the supply.
The higher frequency enabled by SiC allows for the use of smaller and more affordable surrounding components (see Figure 3).
The higher frequency enabled by SiC allows for the use of smaller and more affordable surrounding components. As can be seen, a hybrid approach using SiC MOSFETs requires fewer components, is more cost effective, and achieves a higher power density.
As can be seen, a hybrid approach using SiC MOSFETs requires fewer components, is more cost effective, and achieves a higher power density. This leads to reduced system size, weight, and cost (see Figure 4). Furthermore, in addition to reducing overall energy consumption, the higher efficiency achieved improves thermal performance, leading to additional reductions in the size and weight of the power supply.
Silicon carbide (SiC) offers significant advantages over traditional silicon (Si).
Electric Vehicle Charging
Electric vehicles, require both efficient and fast charging to minimize vehicle downtime. Fast charging stations provide significant advantages over vehicle on-board chargers (OBC), enabling charging times of 30 minutes compared to > 4 hours for OBCs. Charging stations are more flexible as they support hot-swappable power conversion blocks to maximize up-time. Charging stations can also be designed in a scalable fashion, enabling faster time-to-market and lower R&D costs. To be successful, a charging station must provide high efficiency, improved power density, ruggedness, reliability, and bi-directional energy flow for smart grid enablement.
With 2-3 times faster switching, SiC-based chargers have up to 30% lower loses and require 30% fewer components. As can be seen in the block diagram for an AC/DC convertor (see Figure 5), the use of SiC-based components results in a design with fewer components, smaller size, and lower system cost while enabling bi-directional power transfer.
As can be seen in this block diagram for an AC/DC convertor, the use of SiC-based components results in a design with fewer components, smaller size, and lower system cost while enabling bi-directional power transfer.
In addition, the higher efficiency and improved thermal performance of SiC enables higher power density (typically an increase of 65%). This means each station can deliver more power, translating to either faster charging time and or more vehicles charged per station. Currently, the ability to charge more vehicles is typically more important than being able to charge faster. This is because battery technology is behind today’s power supply capabilities which can deliver energy to EV batteries faster than they can be safely charged.
Server Power Supplies
Data centers currently use 3% of all power in the US. This figure is estimated to rise to 15% over the next 7 years. With increasing IoT deployment, data centers – and their associated energy and operational costs – can be expected to become a key consideration in determining the efficiency of industrial systems and smart factories. The advantages of SiC will help improve data center efficiency in many ways over the coming years. For example, SiC-based MOSFETs and diodes utilized in data centers today improve server thermal performance to yield 40% saving in cooling-related energy costs alone.
Wolfspeed SiC – a firm foundation for powering tomorrow
Wolfspeed, A Cree Company, is an innovator of SiC-based power and radio frequency (RF) semiconductors. With more than 30 years of experience in producing and designing with SiC, Wolfspeed is the world leader in SiC technology. Wolfspeed offers a wide portfolio of SiC-based components to help optimize industrial system and power supply designs.
The demand for SiC is growing as the need for lighter, more efficient and cooler power devices grows. Wolfspeed has recently initiated a five-year, $1 billion investment to increase its SiC wafer fabrication capacity and SiC materials production by 30X to meet expected market growth by 2024. The wide bandgap semiconductor components produced will enable dramatic technology shifts currently underway within the automotive, communications infrastructure, and industrial markets.
Wolfspeed SiC is a field-proven technology with industry-leading reliability. It is used in a great many applications, including motor drives, server power, telecom, and electric vehicle charging. During the period from 2010 to 2020, SiC-based power supplies in these applications have logged 6-7 trillion hours of operation and contributed 620 billion kWh in energy savings. Wolfspeed also has the industry’s lowest failure in time (FIT) rate (< 5%).
The unique attributes of silicon carbide promise to radically reduce the amount of energy the world consumes. Wolfspeed SiC provides the industry-leading switching speeds, high performance, and superior thermal capacity power system designers need to build energy conserving power infrastructure.
The world runs on power, and Wolfspeed SiC enables a future where the world can do much more with less.
Dave Skinner is the Senior Product Marketing Manager for the silicon carbide power business at Wolfspeed, a Cree Company. After earning his MSEE and BSEE degrees from Georgia Tech in Atlanta, GA, he began his career with another disruptive high-efficiency power technology, designing class D audio amplifier ICs and systems at Texas Instruments. He has served in a variety of global leadership roles in analog and power semiconductor product development, product marketing, field applications engineering, and sales. Dave also consults with non-profit and charitable-giving organizations to evaluate and recommend technology solutions that remove barriers to learning for people with low vision disabilities.