Four SiC FETs from UnitedSiC deliver lower losses
Silicon carbide (SiC) power semiconductor manufacturer, UnitedSiC, has announced four SiC FETs, with RDS(on) levels as low as 7mOhms. According to the company, they deliver “unprecedented levels of performance and efficiency for use in high-power applications” such as electric vehicle (EV) inverters, high-powered DC/DC converters, high-current battery chargers and solid-state circuit breakers.
Three of the UF3C SiC FET devices are rated at 1,200V with RDS(on) of nine and 16mOhm and one is rated at 650V with RDS(on) of 7mOhm. All four are available in the versatile TO247 package.
The SiC FETs combine a high-performance, third-generation SiC JFET and a cascode-optimised Si MOSFET. This circuit configuration creates a fast, efficient device in a familiar package that can be driven with the same gate voltages as Si IGBTs, Si MOSFETS and SiC MOSFETs, explained the company. To optimise high-temperature operation, silver sintering provides low thermal-resistance mounting for the TO247 package.
The company claims to have achieved the industry’s lowest RDS(on) for any device in this class. In addition, said Anup Bhalla, vice president of engineering at UnitedSiC, the standard drive characteristics and packaging choice enable the SiC FETs to be used as drop-in replacements “for less efficient parts in a variety of applications, with little or no additional design effort”.
The UF3SC065007K4S has a maximum operating voltage of 650V, a drain current of up to 120A, and an RDS(on) of 6.7mOhm. The UF3SC120009K4S has a maximum operating voltage of 1,200V, drain current of up to 120A, and an RDS(on) of 8.6mOhm. Both come in a four-lead Kelvin package, enabling cleaner drive characteristics, added the company.
For lower-power designs, UnitedSiC offers two parts with maximum operating voltages of 1,200V, drain currents of up to 77A, and an RDS(on) of 16mOhm. The UF3SC120016K3S has a three-lead package, while the UF3SC120016K4S has a four-lead package.
The low RDS(on) characteristic enable the SiC FETs to achieve efficiencies of more than 99 per cent in inverter designs, reported the company.
Inverter designers will be able to extract more power from existing designs without reinventing the basic circuit architecture, by switching at the same speed but handling higher currents without excessive resistive heating.
The low switching losses allow designers to operate the inverter at higher frequencies in order to produce a cleaner output current waveform. This improves the efficiency of the motors it drives by reducing their core losses. If the inverter is designed to have a filtered output, higher frequency operation will enable smaller filters.
The parts also work well in parallel to handle very high currents. The combined switching and conduction losses of a 200kW, 8kHz inverter built using six UF3SC120009K4S SiC FETs in parallel has been calculated to be about one third those of a similar inverter built using IGBT/diode modules.
The low conduction losses enabled by the low RDS(on) figures of the UF3C series SiC FETs mean the devices can also be used as solid-state circuit breakers and battery disconnect switches in EVs. The devices can turn off very high currents very quickly, and when used as a circuit breaker have a self-limiting characteristic that controls the peak current that flows. This characteristic can also be used to limit inrush currents flowing into inverters and motors.
The UF3Cseries SiC FETs can form the basis for more efficient high-current battery chargers, claims UnitedSiC. If SiC FETs are used to build a synchronous rectifier to replace the secondary-side diodes, for example, this also dramatically cuts losses and reduces the cooling burden on the charger, added the company.