Even with the undeniable performance and potential of silicon carbide (SiC) technology, some designers may be hesitant initially to tackle new projects using SiC.
Nobody likes to take unnecessary risks. But as with any electronics design project, job No. 1 is to fully understand the requirements and potential of available solutions. From there, designers will find that certain design freedoms enabled by SiC can mitigate any perceived risk.
As SiC technology enters more markets now, designers can realize some exciting new freedoms worthy of exploration. Among them: simplified circuit topologies, smaller systems and enhanced energy density.
First, some background: SiC MOSFETs power systems deliver significant system cost savings, better power density and efficiency, and they run cooler because of much lower energy losses when compared with Si-IGBT or Si-MOSFET. Those undeniable advantages are encouraging as designers explore the benefits of SiC.
Designers looking to stay competitive and lower long-term system costs are turning to SiC-based technologies for many reasons, including these:
- To reduce total cost of ownership: SiC-based designs, while requiring upfront investment, deliver impressive long-term system cost reductions via energy efficiency, smaller system size and reliability.
- To overcome design challenges: SiC’s properties enable designers to develop smaller devices that run cooler, switch faster and withstand higher working voltages.
- To increase reliability and performance: With smaller, cooler devices, designers are free to make more innovative design choices that more readily meet market need.
Let’s explore some key design freedoms in greater detail.
Simple, more efficient topologies
As the need for more efficient, power dense DC/DC and inverters grows, SiC enables simpler topologies and frees designers to get the job done more effectively.
SiC enables replacement of three-level topologies with two-level topologies, thereby providing for easier controlling parameters, taking up less space and emitting less heat.
In Power Factor Correction (PFC) stage hard switching topologies, simple boost (with SiC didoes) and totem pole configurations enable SiC’s low recovery loss. To achieve comparable efficiency with Si-MOSFETs requires more complex topologies and digital control.
SiC can be combined with Si in multilevel topologies to optimize price performance. Here is an example of a modified three-level active neutral point clamped (ANPC) topology used in solar or energy storage inverters:
The pressure is always on for designers to accomplish more in less space. The good news is that SiC designs are smaller, weigh less and support more efficient inverters and storage systems.
Servo drives provide a good example. Servo motors used for object positioning require fast response times to speed up operations. Thus, higher pulse width modulation (PWM) frequencies improve dynamics of servo systems. This requires use of either fast IGBT or SiC as a switch in the servo drive inverter stage.
Using SiC, designers can design-in smaller drives, many of which don’t require active cooling. This freedom means designers can mount a drive directly onto the motor. In such cases, designers can also cable the DC bus directly to the motor with much less electromagnetic noise generation.
Enhanced energy storage
Energy consumers are becoming active power producers, too. SiC’s capabilities in bi-directional power flow help power this change.
Energy storage has been integral to electricity generation, transmission, distribution and consumption for decades. Today, the growth in renewable energy generation requires more reliable power delivery when and where it’s needed.
Energy storage systems provide a wide array of technological approaches to manage energy supply-demand to create a more resilient energy infrastructure and bring cost savings to utilities and consumers.
Electric vehicle (EV) and solar power charging offer good examples of the benefits of bi-directional power flow SiC allows. For example, users of EV and solar power systems, once fully charged, can sell some power back to the utility. Some SiC topologies enable better flow in both directions and improve energy storage systems.
The graphic below displays SiC power densities over Si in solar inverters.
Main benefit: power density increase Si ➝ Si / SiC
- Si Inverter 75kW
- Si / SiC Inverter 150 kW
- Significant improvement in power density
- Cost savings on cooling and weight
- 6 x IFX Easy2B ANPC modules
- 26 x IFX EiceDrivers 1ED-F2
Conclusion: SiC advantages over Si
- 50% lower energy loss
- 10 times smaller system size
- 100 times higher frequency operation
- Faster on-and-off performance
- Higher voltage operation