2023 May be the Year You Try Silicon Carbide: Here’s Why

Silicon (Si) remains the dominant material for power semiconductors. But developments related to silicon carbide (SiC) may tempt more designers to try the new material in 2023. Will you be one of them?

SiC suppliers like Wolfspeed and STMicroelectronics are betting you will. They have announced the move to 200 millimeter (mm) wafers, which are 1.7 times larger than today’s 150 mm wafers. Those larger wafers will have more chips per wafer, driving down the cost of SiC devices. The timing is perfect; demand for power conversion in electric vehicles (EVs), green energy and the smart grid, and a range of Industry 4.0 systems that can benefit from using SiC is set to surge, just as the availability of SiC is increasing.

Let’s briefly look at the performance benefits of SiC and how the new 200 mm wafers are being fabricated. We’ll then present SiC devices and modules from Wolfspeed and STMicroelectronics, along with development platforms to speed the development of SiC-based power converters and motor drives, including a kilowatt (kW) class power factor correction (PFC) circuit using discrete SiC MOSFETs, and a 300 kW three-phase power converter based on SiC power modules.

SiC performance

SiC isn’t perfect, but it does offer several benefits compared with gallium nitride on silicon (GaN on Si) and Si power devices, including a lower rise in R_DS(on) with temperature. Conduction losses are directly impacted by R_DS(on) that’s typically specified at 25°C, and due to the lower R_DS(on) increase with temperature, a 60 milliohm (mΩ) SiC device will have performance similar to 40 mΩ Si and GaN devices at operating junction temperatures. Other parameters like thermal conductivity and die size favor SiC. Cost is clearly an advantage for Si, and so are hours of field experience, available levels of integration, and packaging styles (Table 1). In each of those cases, the advantage of Si is expected to continue to narrow.

Table 1 : The operating characteristics of SiC make it well-suited for transportation, green energy, and Industry 4.0 applications. (Image source: Wolfspeed)

More SiC coming soon

One of the biggest factors contributing to reducing the cost advantage of Si will be increased production volumes of SiC. Most SiC makers are ramping up production as quickly as practical. Two examples cited here are Wolfspeed and STMicroelectronics. Wolfspeed is building a multibillion-dollar SiC materials manufacturing facility for 200 mm wafers that will increase its production capacity by ten times when fully operational (Figure 1).

Figure 1: Wolfspeed’s new 200 mm wafers will boost its SiC capacity by 10x. (Image source: Wolfspeed)

STMicroelectronics is also developing 200 mm SiC capability and has partnered with Soitec to use the company’s Smart Cut technology for next-generation SiC substrates. Smart Cut is expected to reduce SiC wafer costs, improve quality, and boost yields.

kW class totem-pole PFC reference design

If you’re designing a kW class alternating current (AC) input power converter like a direct current (DC) output power supply, uninterruptible power supply (UPS), or motor drive, you might be considering a totem-pole PFC stage. If so, you can turn to the STEVAL-DPSTPFC1 bridgeless totem-pole reference design from STMicroelectronics that handles 3.6 kW, with an input of 230 volts alternating current (VAC) at 50 Hertz (Hz), or 1.6 kW, with an input of 110 VAC at 60 Hz. It includes a digital PFC and an inrush current limiter. This design uses 650 volt SiC MOSFETs (SCTW35N65G2V), Si SCRs (silicon-controlled rectifiers) (TN3050H-12WY), isolated FET drivers (STGAP2S), and a 32-bit MCU (STM32F334).

This PFC runs at 72 kilohertz (kHz) with a peak efficiency of 97.5% and a total harmonic distortion (THD) of 3.7%, typical. The reference design includes a power board with a bridgeless totem-pole boost circuit with an inrush limiter and auxiliary power supply, an MCU-based control board with PFC and current-limiting control firmware, plus an adapter board for software debugging (Figure 2).

Figure 2: The STEVAL-DPSTPFC1 is a complete kW class bridgeless totem-pole PFC design. (Image source: STMicroelectronics)

300 kW high-frequency, three-phase SiC inverter

If you’re designing traction inverters, energy storage systems or large UPSs, smart grid devices like flexible AC transmission systems, or large industrial motor drives, you can use the CRD300DA12E-XM3 300 kW three-phase inverter from Wolfspeed. This inverter can operate from 20 to 80 kHz, and you can use it to explore the performance capabilities of SiC power modules. This reference design includes three CAB450M12XM3 1200 volt, 450 ampere (A) SiC half-bridge modules, and three CGD12HBXMP gate drivers. The inverter is a complete solution including power modules, liquid-cooled cold plate, power bussing, gate drivers, voltage and current sensors, and the controller (Figure 3). Specifications include:

• 800 VDC power bus (900 VDC, maximum)
• 360 A root mean square (rms) output
• 300 microfarad (μF) DC link capacitance
• CAN bus communications

Figure 3: The CRD200DA12E-XM3 inverter based on SiC power modules can handle up to 300 kW. (Image source: Wolfspeed)Figure 3: The CRD200DA12E-XM3 inverter based on SiC power modules can handle up to 300 kW. (Image source: Wolfspeed)

Conclusion

The use of SiC for power conversion is set to grow rapidly as the transition from 150 to 200 mm wafers drives down the cost of SiC devices. This blog has reviewed the performance benefits of SiC and presented a kW class totem pole PFC and a 300 kW inverter using SiC. Will you be tempted to try SiC in 2023?

Recommended Reading

How to Make Energy Infrastructure More Efficient and Reliable While Reducing Cost

When and How to Use Bridgeless Totem-Pole Power Factor Correction

Use SiC-Based MOSFETs to Improve Power Conversion Efficiency