SiC JFET die can be packaged with controller IC for fast flyback devices

SiC JFET die, available from UnitedSiC can be co-packaged with a controller IC. The die has a built-in, low voltage MOSFET to fabricate an extremely fast, cascode-based, 20 to 100W flyback device.

UnitedSiC has announced seven die currently available in wafer form only. Voltage ratings range from 650 to 1700V and RDS(on) is as low as 140mOhm. Three die sizes are available down to 0.8 x 0.8mm for ease of co-packaging.

Ranging from 650 to 1700V, the normally-on SiC JFETs enable simplified start-up implementation with zero standby dissipation. They are particularly suitable for large flyback AC/DC applications market, such as consumer market adapters and auxiliary power supplies. Typical low-power flyback applications are laptop and mobile device chargers (from 20 to 65W). Other applications range from wide-input (up to 1400V) flyback auxiliary supplies for industrial applications such as motor drives to high power lighting applications such as long LED chains.

The small die sizes with very low RDS(on) and capacitances will appeal to controller IC manufacturers. The normally-on JFET helps meet light and no-load dissipation regulations when coupled with a low Qg, low voltage MOSFET integrated in the controller IC, explains UnitedSiC.

The inherent capability of SiC JFETs in terms of handling repeated avalanche and short circuits mean that SiC cascodes are extremely robust. The SiC JFET is in series with the LV MOSFET in the control IC. The source of the normally-on JFET rises to 12V before JFET turns off and the IC begins switching. This current path through the JFET can be used as a start-up supply for the controller IC. An auxiliary supply from the converter transformer is then gated-in when the converter starts running, with no further dissipation.

UnitedSiC develops innovative silicon carbide (SiC) FET and diode power semiconductors that deliver the industry’s best SiC efficiency and performance for electric vehicle (EV) chargers, DC/DC converters and traction drives, as well as telecom/server power supplies variable speed motor drives and solar photovoltaic (PV) inverters. 

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