This article appeared in Electronic Design and has been published here with permission.
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According to onsemi, its three new 1700-V silicon-carbide (SiC) devices have what it takes to run the high-voltage electronics at the core of EV charging stations, industrial drives, solar inverters, and renewable-energy equipment.
As part of its newly named EliteSiC family of technologies, the company said the NTH4L028N170M1 1700-V MOSFET brings higher breakdown-voltage (BV) ratings, which are required to support a new generation of industrial-grade power gear.
Also launched at CES 2023, onsemi introduced a pair of 1700-V avalanche-rated Schottky diodes, the NDSH25170A and NDSH10170A, designed to run reliably at elevated temperatures while offering the high-efficiency enabled by SiC.
SiC belongs to a class of wide-bandgap semiconductors that are upending the world of power electronics. Its unique properties enable it to distribute power in a way that limits losses while dissipating less heat than silicon.
The heartiness of the new material also helps it safely handle BVs totaling thousands of volts—approximately 10X the amount that silicon MOSFETs and IGBTs, which have dominated for decades, can tolerate.
Fast-switching properties give the chips the edge in energy efficiency, even though they tend to cost more than silicon chips. That quality also enables the immediate power stage to be surrounded with smaller transformers and passive components, which are usually the largest and most expensive parts in a system. Coupled with its energy efficiency, SiC can effectively reduce the weight and bulkiness of power supplies that previously featured silicon.
Resisting Resistance
With its new family of 1700-V SiC devices, the company is trying to stay a step ahead of purveyors of solar inverters, wind turbines, and other renewable-energy grid equipment, including battery storage, which are all upgrading to more hazardous high voltages. Today, new solar inverters are moving from 1100-V to 1500-V dc buses, which require power switches with higher BVs for the sake of safety and reliability.
The 28-mΩ, 1700-V MOSFET has a maximum operating gate-voltage range (Vgs) of −15 to 25 V. That’s ideal for fast-switching systems where voltages are increasing to −10 V to improve system reliability, said onsemi.
Due to its high durability, SiC MOSFETs can handle high voltages over a shorter distance through the device and, as a result, reduce the electrical resistance—also called the RDS(on) or the resistance between the drain and source regions of the device during on-state operation—of the device. This curtails power losses when the MOSFET converts power from one level to another, giving it greater energy-efficiency relative to IGBTs.
Thermal conductivity in SiC is 3X higher than in silicon, enabling better heat dissipation. Its ability to whisk heat from the system reduces thermal stress on the device and eases cooling requirements.
Based on onsemi’s planar SiC technology, the 1700-V SiC MOSFET supports a total gate charge (Qg)—or the amount of charge required to drive the device—of 200 nC when operating at 1200 V at 40 A. That compares to rival chips clocking in closer to 300 nC, according to onsemi. Keeping gate charge in check is critical to squeezing more electricity out of renewable energy sources such as solar panels.
The 1700-V MOSFET housed in a TO247-4LD package, is priced at $29.59 per unit.
Diodes on Tap, Too
The new diode devices belonging to the EliteSiC family have a voltage rating of 1700 V and deliver improved margin between the maximum repetitive reverse voltage (VRRM) and the peak repetitive reverse voltage of the diode.
The power-handling properties of SiC also keep leakage current in check. As a result, the current fluctuates less over a wider range of temperatures than silicon IGBTs and MOSFETs. The new parts exhibit big improvements in reverse leakage performance, with a maximum reverse current (IR) of 40 µA at 25°C and 100 µA at 175°C. These ratings are significantly better than rival solutions that are often rated at 100 µA at 25°C, said onsemi.
The company has been aggressively building up its power electronics business in recent years, battling the likes of Infineon, Microchip, and Wolfspeed in the world of power electronics based on SiC.
It’s expanding production capacity for raw materials—the cylindrical bars of silicon carbide called boules. The intention is to shore up its supply of a semiconductor critical to the future of electric cars and renewable-powered electric grids that the world is turning to cut carbon emissions. Investments also are being made in its wafer fabs. Plans are to double its output of SiC chips in 2023 after ramping up production 3X last year.
The company’s leadership anticipates sales of its SiC devices to surge to more than $1 billion in 2023.
Separately, onsemi said solar-power equipment supplier Ampt uses SiC MOSFETs from its EliteSiC family to handle critical power switching in Ampt’s dc string optimizers for large-scale solar and energy-storage systems.
Ampt’s string optimizers are key building blocks in modern solar-power plants, ferrying power from the solar panels at a high and fixed voltage ranging from 600 to 1500 V dc, reducing the overall current requirements and, by extension, the cost of the system. By using onsemi’s SiC MOSEFTs, Ampt said that it can boost round-trip (charging and discharging) efficiency in energy-storage systems and solar-power plants.
Check out more of our CES 2023 coverage.
