Silicon carbide (SiC) is a wide-bandgap semiconductor material that has enhanced performance characteristics compared with traditional silicon-based devices. This facilitates enhanced energy efficiency and improved power management across a wide range of applications.
A SiC power device has enhanced operational capabilities in terms of temperature tolerance and efficiency due to its reduced power losses and increased bandgap. This enables the device to operate reliably across a broader range of temperatures without experiencing any detrimental effects on its performance or efficiency. These characteristics, together with the property of chemical inertness, enhance the significance of SiC in the realm of power electronics, hence promoting its utilization and dissemination across many applications. SiC power devices find extensive utilization in various domains, including power supplies, battery electric vehicles, power-conversion systems for battery charging and traction drives, industrial motor drives and renewable-energy–generation systems like solar and wind inverters.
This article centers its attention on the use of SiC in the industrial and automotive sectors, specifically highlighting the activities of WeEn Semiconductor, an international corporation that specializes in the research, production and distribution of SiC power devices.
The relevance of SiC
With its proficiency in SiC and bipolar power devices, WeEn Semiconductor endeavors to provide a valuable contribution to the advancement of sustainable energy solutions, efficient power management systems and sophisticated electronic products. SiC power devices possess several advantageous characteristics over traditional silicon-based devices, such as a larger bandgap, lower intrinsic carrier density, higher thermal conductivity and higher saturation velocity. Consequently, these material properties enable SiC power devices to offer numerous benefits when compared with other alternatives.
These advantages encompass a reduced specific on-resistance (RDS(on)) at a given voltage level, a higher-voltage capability compared with silicon (e.g., up to 15 kV for SiC MOSFETs, in contrast with the 6.5 kV of silicon IGBTs) and significantly lower capacitances owing to the compact package size associated with a given RDS(on).
The integration of reduced conduction and switching loss, increased switching frequencies and simplified cooling demands can yield decreased power-conversion losses, enhanced efficiency, streamlined converter topologies and notable advancements in high-temperature capabilities and performance, as well as diminished system dimensions, weight and expenses.
SiC can operate at temperatures higher than silicon without suffering a discernible drop in performance. This demonstrates that SiC components can function in high-temperature conditions without suffering any performance degradation. In addition, SiC devices can manage a greater amount of power within a smaller package than silicon devices can. This enables both an increase in power density as well as a reduction in the size and weight of the system. Silicon has a higher resistance to both electric shock and the damaging effects of the environment, while SiC has an even higher resistance. As a consequence, the resulting devices are sturdier and more trustworthy, making them appropriate for a wider variety of mission-critical applications.
There have been several technological hurdles along with the commercialization and evolution of planar technology SiC MOSFETs. However, over time, the dependability of the gate oxide has also greatly improved. The gate oxide, as well as the methods that can be used to protect it from high electric fields, continues to be a primary area of emphasis in device development. It is also vital to improve screening tests to filter out dies that have the potential to have parametric drifts over time.
To manufacture dependable SiC MOSFETs, the density of gate oxide defects must be reduced to a minimum throughout the production stage. In addition, novel screening procedures need to be developed to discover and eliminate potentially compromised devices.
The next generation of WeEn’s SiC devices will make use of a structure known as a “trench,” which is characterized by the precise etching of trenches into the SiC material. Within this structure can be found the active zone of the device as well as the channel. The gate electrode is often positioned within the trench, which encircles the channel and allows for superior control over the distribution of the electric field in comparison with planar devices. The use of trench devices has several advantages, including a lower ignition resistance and an increased switching performance because of better gate control. Figure 1 shows the technological advancements that have been made in the SiC MOSFET throughout the years.
SiC MOSFETs
SiC MOSFETs have found an optimal application space in EV traction inverters. The efficiency and size of the inverter system have increased due to their increased switching frequency, decreased leakage and enhanced performance at high temperatures. Customers can benefit from an increased driving range per battery charge. The total addressable market for SiC was approximately $1 billion in 2022. By 2028, analysts anticipate growth to reach $5 billion. Silicon IGBTs currently dominate the low- and medium-power (150 kW) inverter market, but this is swiftly changing as the use of SiC increases, particularly in the >80-kW market. SiC devices dominate the market for EVs, SUVs and high-performance trucks with power ratings above 200 kW.
WeEn’s first planar technology SiC MOSFETs have a voltage of 1,200 V and have RDS(on) values of 160 mΩ, 80 mΩ and up to 12 mΩ. TO247-3L and TO247-4L packages are available, along with other industry-specific ones. Other solutions are 650 V and 1,700 V.
The short-circuit capability of SiC MOSFETs depends on the gate-to-source voltage (Vgs) and drain-to-source voltage (Vds) at the time of short-circuit. WeEn proposes that the short-circuit capability of a SiC MOSFET is affected by the voltage levels provided at its Vgs and Vds during the short-circuit event. These voltage levels affect the behavior of the MOSFET during the short-circuit event.
This suggests that decreasing Vgs and Vds can increase the SiC MOSFET’s short-circuit withstand time (SCWT). SCWT is the MOSFET’s short-circuit resistance before injury or thermal runaway. At 18 V and 800 V, the SCWT of WeEn’s second-generation MOSes is 3.5 µs with secure shutdown and no thermal runaway. WeEn’s second-generation SiC MOSFET is functional under these conditions. When Vgs is 18 V and Vds is 800 V, the SiC MOSFET can tolerate a short-circuit for 3.5 µs without thermal runaway.
WeEn’s SiC MOSFET has a competitively low Ronsp (2.6 m-cm2), demonstrating the technology’s benefits. A low Ronsp value indicates reduced power losses and increased switching efficiency, highlighting the benefits of SiC technology.
WeEn’s SiC MOSFET employs a transparent naming convention to indicate RDS(on) at 15-V gate-drive voltage. The optimized gate oxide enables the device to operate normally with a 15-V gate-drive voltage, making it simpler to implement in conventional designs. The optimized gate oxide enables MOSFETs to operate reliably at this gate-drive voltage, easing their incorporation into existing conventional designs. WeEn conducted the corresponding reliability test using a range of Vgs from 12 to 24 V to ensure the robustness of the gate in wide drive scenarios.
The N-channel SiC MOSFET WNSC2M20120B7 has a low on-resistance of 20 mΩ. High switching speeds enable rapid transitions between the on and off states. This feature is advantageous for applications requiring operation at a high frequency. Additionally, the MOSFET can be turned off with a 0-V gate voltage, which simplifies the gate-driver circuit and reduces the complexity of the control circuit. Because of the high efficiency and low power losses of SiC MOSFETs, system cooling requirements can be decreased, resulting in smaller and less expensive cooling solutions.
Typical applications include:
- Switch-mode power supplies (SMPS). SMPSes are used in a variety of electronic devices, including computers, televisions, audio systems and more, as independent power supplies. They convert AC power from the mains to the DC voltage efficiently required for electronic circuits.
- Uninterruptible power supplies (UPSes): UPS systems provide reserve power during power outages and voltage fluctuations using SMPS technology. SMPS-based UPSes are more efficient, more compact and provide superior power management than transformer-based UPS systems.
- Solar string inverter and solar optimizer: Solar PV systems use string inverters and optimizers based on SMPSes. Inverters transform the direct current produced by solar panels into alternating current for grid connection, while optimizers increase energy efficiency by monitoring and optimizing the output of each solar panel. SMPS technology facilitates maximum power-point tracking and ensures high conversion efficiency.
- EV battery chargers: These use SMPS technology to convert the grid’s alternating current into direct current to charge the EV battery. SMPS-based chargers offer high efficiency, compact size and the ability to provide the requisite power levels for rapid charging, thereby promoting the adoption of EVs.
- Motor drives: SMPS technology is widely used to govern the speed and torque of electric motors in motor drives. By utilizing SMPS-based motor drives, the efficacy of motor control can be significantly enhanced, resulting in energy savings, precise control and enhanced motor performance overall.
WeEn Semiconductor provides its customers with efficient, dependable and high-quality power devices. To satisfy the changing demands of a variety of industries, the company prioritizes continuous innovation and technological advancement. Increased efficiency and the resulting decrease in application temperature will enhance the project’s dependability.
