Why haven't SiC devices replaced IGBTs?

The production process and technology of silicon carbide (SiC) devices have become more and more mature. It includes the cost of R&D and production and the cost of driving capacitance resistance in the whole circuit after replacing IGBT with SIC device in application. Unless the manufacturer does it, and it does reduce costs and improve performance. After all, adopting something new can be costly. Limited by the impact of manufacturing cost and product yield, the main reason that prevents SiC products from entering the market on a large scale is the high price, which is generally about 10 times that of similar Si products. Although said in the future with technical improvement and cost reduction, silicon carbide (SiC) devices to replace IGBT is inevitable silicon carbide (SiC) devices, performance may be very strong, but really can become a trend not only to the performance, but also cost, reliability on the multiple guarantee.



The application advantage of silicon carbide device is obvious

High efficiency, high reliability: SiC BJT products achieve high efficiency, current density and reliability, and are able to work smoothly at high temperatures. In addition, SiC BJT has excellent temperature stability, at high temperature working characteristics with room temperature no difference. SiC BJTS offer all of the benefits of IGBTs and solve all of the design bottlenecks with IGBTs. Since IGBTs are voltage driven and SiC BJTS are current driven, the design engineer replacing IGBTs with SiC BJTS may not be comfortable at first, but component suppliers, such as Fairchild Semiconductor, generally provide reference designs to help the engineer design the drive line. In the future, the use of SiC BJT will be more simplified after the launch of the dedicated driver chip.

Low loss, can reduce the cost

The Vce of SiC BJT was reduced by 47%, the Eon by 60% and the Eoff by 67%. SiC BJTS provide the lowest conduction loss on the market with Ron of less than 2.2 milliohms per square centimeter at room temperature. SiC BJTS provide minimal total loss, including drive loss. SiC BJTS are the most efficient 1200V power transfer switch ever made. SiC BJTS achieve higher switching frequencies with lower conduction and switching losses than IGBTs (30-50%), enabling up to 40% output power increases in systems of the same size. 2KW from 400V to 800V booster circuit, with silicon IGBT can only achieve 25 KHZ switching frequency, and need to use 5 film capacitors, and with SiC BJT, not only the switching frequency can do 72KHz, and only need to use 2 film capacitors, radiator size, inductance size are reduced by one third, In other words, the total BOM cost of the system can be greatly saved by using smaller inductance.

Improve the switching frequency of power supply to achieve high frequency

The biggest disadvantage of traditional IGBT is the slow switching speed and low working frequency. It has a current tail when it is turned off, which will cause high turn-off loss. SiC BJT switch fast and no IGBT off is the current tail, so the switching loss is very low. SiC BJTS also have lower on-off resistance than IGBT VCE(sat) at the same voltage rating, which can reduce conduction losses. The best application of SiC BJT is more than 3000W power supply design, this kind of power supply is a lot of IGBT to do switching devices, in order to achieve the cost and efficiency of the optimization. If the design engineer uses the SiC BJT to replace the IGBT, it is easy to greatly increase the switching frequency of the power supply, thus reducing the volume of the product and improving the conversion efficiency. Due to the increase in frequency, the design can also reduce the number of inductors and capacitors required by the peripheral circuit, which helps to save costs. On the other hand, SiC BJT has a fast switching speed, which can complete the switching action in less than 20nS. This speed is even faster than MOSFETs, so it can also be used to replace MosFETs. Compared with bipolar IGBT devices, SiC BJT has lower conduction resistance and can further reduce the conduction loss. SiC BJT's high temperature stability, low leakage, are beyond IGBT and MOSFET. In addition, its internal resistance is positive temperature coefficient change, easy to use in parallel for high power supply design.