Silicon Carbide (SiC), an ultra wide band-gap semiconductor material, is growing increasingly popular as an industrial voltage source converter component. SiC can withstand higher temperatures and voltages than silicon; German manufacturer Danfoss operates an SiC Center of Excellence consisting of offices and a 600m2 lab dedicated to developing and testing power semiconductors.
SPT testing compared the switching characteristics of SiC-IGBTs to those of traditional Si-IGBTs, showing that SiC-IGBTs could improve efficiency and hard-switching behavior.
Efficiency
Silicon Carbide (SiC) MOSFETs feature lower switching loss than their silicon (Si) counterparts, resulting in higher efficiency and reduced thermal losses. Furthermore, SiC devices can operate at higher temperatures and voltages compared to traditional silicon ones – making them the perfect choice for industrial power converters.
SiC IGBTs are transistors made using insulated gate bipolar transistor (IGBT) technology, providing high input impedance and current density – ideal characteristics for high-frequency power converters. Furthermore, their lower RDS(ON) voltage drop than silicon MOSFETs reduce parasitic losses and boost switching performance, thus improving performance significantly.
SiC IGBTs outshone traditional silicon power chips by being capable of switching at twice their switching speed with much lower current capabilities, providing faster and more efficient inverter operation and decreasing capacitor sizes; saving both space and weight within an inverter – especially important when used to power planes’ ground power stations.
Danfoss has introduced a silicon carbide power module designed for DC to AC motor drives that is intended to deliver maximum efficiency and reliability for applications including e-mobility, solar inverters, and other uses. Constructed using high-quality SiC power semiconductors which conduct electricity more efficiently than their conventional counterparts – helping lower energy costs, reduce the size of inverters, and eliminate costly cooling systems altogether.
Switching Characteristics
Silicon Carbide (SiC) is a wide band gap compound semiconductor capable of operating at high temperatures and voltages. Doped n-type with nitrogen or phosphorous and doped p-type with beryllium, boron, aluminum, or gallium as appropriate can produce either p or n type properties depending on doping type; for example beryllium may also be added as doping agent in hard switching applications. German company Semikron Danfoss conducted tests comparing switching characteristics between SiC power switches compared with traditional insulated-gate bipolar transistors (IGBTs); results indicated that SiC devices were more efficient in hard switching applications.
Research team utilized a standard test system to assess the efficiency and detailed hard-switching behavior of SiC-IGBT modules, testing both single pulse test-based systems as well as three phase systems. At least 77% efficiency was observed in single pulse testing applications while up to 92% efficiency could be reached within six switch AGPU systems.
Hybrid power switches combine the advantages of unipolar and bipolar devices to increase efficiency in high-voltage applications. They feature low transconductance and can switch the same voltage at higher frequencies than IGBTs for reduced total power losses in systems, making hybrid switches an excellent solution for AC-DC converters with limited space and fewer peripheral components; their reduced size results in lower energy losses, weight, capacitor volume requirements, network losses as well as being sized according to demanding specifications allowing deployment across a wider variety of applications than IGBTs alone.
Cost
Silicon carbide (SiC) has quickly emerged as an attractive wide bandgap semiconductor solution to power electronics for use in 21st Century applications, providing compelling cost of ownership over lifetime comparisons to silicon-based devices and many other advantages; including its thinner device with same breakdown voltage providing reduced on resistance per unit area.
SiC’s lighter passive component volumes allow for smaller systems in terms of size and weight savings, with reduced energy losses, improved efficiency, increased reliability, and significantly decreased system size/weight requirements. SiC MOSFETs have quickly become mainstream among electric vehicle (EV) inverter applications with significant market penetration; additionally they are increasingly available as bare die devices, giving manufacturers the opportunity to create custom inverter modules.
SiC’s high switching frequencies and low power losses allow it to provide higher system energy density. To maximize this benefit, however, one must take into account both filter and heat sink volumes in addition to switching frequency/efficiency balance of converters in order to optimise these volumes.
SiC substrate costs remain the main driver of its total costs, outweighing contributions from epitaxy, fabrication and yield. However, hybrid modules such as CoolSiC can help bridge this gap by combining IGBTs with SiC diodes.
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