UnitedSiC has announced new additions to their 650V silicon carbide cascode FET family—just in time for PCIM.

With PCIM taking place this week, the spotlight is on power devices, and UnitedSiC is announcing additions to its UF3C and UJ3C series. The units are aimed at serving in data center power supplies, 5G base station telecom rectifiers, and in onboard electric vehicle chargers.


Image from UnitedSiC


Cascode-Based Devices

Members of both series from UnitedSiC are based on the cascode configuration. In this unique relationship, a high performance, wide bandgap SiC (silicon carbide) fast JFET is co-packaged with silicon MOSFET. The advantage here is that the MOSFET, which is controlled with a very low input voltage, can itself control a very high-voltage JFET.


Low-voltage MOSFET controls a high voltage JFET. Image from UnitedSiC


Members of both series will be available in T0220 and D2PAK packages, and are intended as “drop-in replacement” devices for existing silicon IGBTs, silicon FETs, SiC MOSFETs or silicon superjunction devices.

Both series of SiC FETs are based on pairing a normally-on SiC JFET with a Si MOSFET to produce a normally-off SiC FET device, as illustrated above. As a result, existing systems can be upgraded with the UnitedSiC device serving as a “drop-in replacement” FET. Thus, with no need to change gate drive voltage, designers can expect a performance increase with lower conduction and switching losses, enhanced thermal properties and integrated gate ESD protection.

In the case of new designs, the units can allow designers to build around increased switching frequencies. This allows for the employment of far smaller passive components, such as magnetics and capacitors. This is meant to result in substantial system benefits, such as increases in efficiency and in reduction in size, weight, and cost.

Some members of the series will be available in automotive versions that meet AEC-Q101. A complete listing of both the existing and the seven new members of both the UF3C and UJ3C series can be found here, mid-page.

UnitedSiC will be showcasing the UF3C and the UJ3C series at PCIM (in Hall 7 at booth 406, for those of you attending).


Hard Switching and Soft Switching

Members of the UF3C series are hard switched, while UJ3C devices are soft switched. Each method has different advantages and disadvantages.

Hard switched devices switch at a predetermined frequency. While they are simple to design, there may be overlap between the output’s voltage and current waveforms, which can result in switching losses.

Soft-switching converters require control circuitry to coordinate the switch time with the output’s waveforms. They are more complex than hard-switching converters, as the switching point needs modification. Because switching speed will be lower, larger and heavier output filtering components are required.


What Other Manufacturers Have on Offer

With today’s emphasis on power electronics, there are many participants in this field. Here are two of the many available choices:

SSDI’s SGF46E70 and SGF15E100 families are cascode devices combining a GaN HEMT (high-electron-mobility transistor) with a low-voltage silicon MOSFET. These devices are designed for demanding aerospace and defense applications.

The TP65H035WS from Transphorm is a 650 V device combining a high-voltage GaN HEMT with a low-voltage silicon MOSFET. It is designed for service in datacom, solar inverter, and servo motor devices, as well as in a broad range of industrial applications.



In which applications have you used SiC? What are your personal experiences with SiC FETs? Share your thoughts in the comments below.