Power Electronics Europe April/May Issue 2022

www.microchip.com/en-us/product/MOSFET-SIC-1700V SILICON CARBIDE 17 www.power-mag.com Issue 2 2022 Power Electronics Europe might there be for a 1700V transistor? Though there is just one, it is ubiquitous: Found in every power electronics system, the auxiliary power supply (AuxPS) is essential to the routine operation of industrial motor drives, electric vehicles, data center and backup power, solar inverters, charging infrastructure, and more. The AuxPS is system critical because it provides power to gate drivers, sensing and control circuits, and cooling fans; consequently, the AuxPS must not fail, and any associated risks should be mitigated. Because these low-power, isolated, switch-mode power supplies are used in diverse applications, they must accept a wide-ranging, high-voltage dc input (300 to 1000 V) and output a low-voltage (5 to 48 V) source. Perhaps the most powerful method of failure mitigation is a simplified circuit design. As shown in Figure 2, the most reliable circuit design is the single- switch flyback topology (Figure 2, right), which offers simplicity and reduced component count – the latter adding a benefit of lower overall cost. The introduction of 1700 V SiC MOSFETs provides an ideal solution for the AuxPS. Combining a high breakdown voltage, lower specific on-resistance, and fast switching speed, these devices are well-suited for the single-switch flyback topology. In contrast, Silicon-based solutions either have too low voltage rating, which necessitates a two-switch architecture (shown in Figure 2, left) and doubles the possibility of failure; or they have an adequate voltage rating but poor performance, few suppliers, and compared to SiC, a higher price. Beyond the improved reliability, simpler control scheme, reduced component count, and lower cost, an AuxPS utilizing 1700 V SiC MOSFETs can also be smaller. The area-normalized on-state resistance, also called specific on-resistance ( Ron,sp ), of SiC MOSFETs is a fraction of that for Silicon MOSFETs. This means smaller packages may be used for the smaller die, and conduction losses are reduced which can ultimately result in smaller (or completely removed) heat sinks. Furthermore, SiC MOSFETs have lower switching losses, providing a pathway to shrink transformer Figure 2: The two-switch topology (left) using Silicon transistors can be replaced with the much simpler single-switch flyback (right) using better- performing and lower-priced 1700V SiC MOSFETs Figure 3: The complicated three-level circuit topologies (left) using Silicon IGBTs can be simplified to the more elegant and reliable two-level topology (right) using half (or fewer) 1700 V SiC MOSFET power modules size, weight, and cost by increasing the switching frequency. Tens to hundreds of kilowatts Moving up the power range, 1700V SiC MOSFETs also provide many advantages over Silicon MOSFETs and IGBTs in applications ranging from tens to hundreds of kilowatts. Examples include string and central solar inverters, auxiliary power units (APUs) in commercial transportation vehicles, induction heating and welding machines, industrial drives, wind converters, and more. As the processed power increases, so does the impact of SiC’s faster, more efficient switching. Compared to the Silicon IGBT, SiC MOSFETs reduce switching losses by an average of 80 %, allowing converters to increase switching frequency and shrink the size, weight, and cost of bulky, expensive transformers. And though the conduction losses of SiC MOSFETs and Silicon IGBTs are similar under heavy loads, many applications spend most of their service lifetimes operating under so-