March 24, 2020
This blog post was first published by United Silicon Carbide (UnitedSiC) which joined the Qorvo family in November 2021. UnitedSiC is a leading manufacturer of silicon carbide (SiC) power semiconductors and expands Qorvo's reach into the fast-growing markets for electric vehicles (EVs), industrial power, circuit protection, renewables and data center power.
With the pace of innovation in sectors like EV, renewable energy and 5G increasing at a rate of knots, engineers are increasingly looking for new solutions and demanding more from technology to meet consumer and industry demand. SiC semiconductors are one answer and they are on an exciting road of improvement, already delivering cost-competitive performance compared with older technologies.Blog
Oscar Wilde, the Irish poet, novelist and raconteur wrote in his play ‘Lady Windermere’s fan’ that a cynic is someone who “knows the price of everything and the value of nothing”. It was meant to be a put-down of people taking the short-sighted view of a situation without seeing the wider picture. He contrasts a cynic with a ‘visionary’ who focuses on benefits rather than cost.
Power engineers need to be a bit of both; the price of components they specify can’t be ignored but there is always a cost-benefit relationship which is complex, changing over time and often difficult to quantify. Power semiconductors are an example. The innovative and relatively recent disruptive technology of SiC was necessarily expensive when first commercialized and most engineers put it a long way down their ‘nice to have’ list, although recognizing the potential advantages over silicon-based products such as IGBTs and Si-MOSFETs. However, as SiC prices have fallen, their performance improved and their reliability demonstrated, they have moved up the list and can now be considered as a replacement for existing older technology parts and a starting point for new designs. Their take-up has been application dependent; solar and EV engineers have been early adopters where efficiency improvements have been a high priority, but with die costs falling, performance improving and the value of energy savings and lower associated component costs factored in, there really is no reason not to ‘make the switch’ in a much wider range of applications.
Figure 1: SiC system cost is lower than an IGBT solution
Even if the inherent advantages of SiC were not enough: high critical breakdown voltage; high-temperature operation; excellent figures of merit for on-resistance with die area and switching losses; fast switching and much more, the latest ‘Generation 3’ SiC-FET devices from UnitedSiC using normally-off cascodes have pushed the boundaries further still. Latest products in our UF series have the lowest-in-class on-resistance for 1200V and 650V devices, at less than 9 milliohms and 7 milliohms respectively. The devices have a low-loss body diode effect, are inherently robust with overvoltages and short circuits and are as easy as Si-MOSFETs or IGBTs to drive. In fact, with TO-247 packages they can be a drop-in replacement for many of these parts, providing an instant performance boost. For new designs, UnitedSiC has also introduced a low-inductance, thermally enhanced DFN8x8 package which leverages the high-frequency capabilities if SiC-FETs.
Figure 2: SiC FETs gate drive is compatible with existing technology with superior gate protection
System energy efficiency savings are increasingly tipping design decisions in favour of SiC-FETs with the ‘visionaries’ adding in the user and environmental benefits to the value equation. There is more to be had though; if systems are designed around SiC-FETs, switching frequencies can be raised without significantly hurting efficiency and components could even be eliminated such as discrete commutation diodes and snubber networks. Then there is the consequent reduction in size, weight and cost of other associated components such as heatsinks, inductors/transformers and capacitors. In the extreme, whole cooling systems with their own inefficiencies could be made redundant with even more savings. In EV traction inverter applications particularly, there is a virtuous circle of efficiency improvement giving a better range from a battery charge with yet further range added because of smaller and lighter components in a SiC-based inverter.
SiC technology is still evolving with the promise of better performance to come. In the next generation, on-resistances will fall further along with switching losses, rated voltages will increase, die will shrink further and yields improve, leading to lower costs. More variants will appear with a wider selection of packages suiting an increased range of applications at higher voltages and power levels.
Oscar Wilde also said, “Success is a science; if you have the conditions, you get the result”. The conditions are right for success with SiC and will only get better. If you do the value calculation, you might be surprised at the cost of not innovating with UnitedSiC products.
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