Simple silicon substitution to cut losses in power systems

Drop-in replacements for silicon superjunction MOSFETs have been unveiled by UnitedSiC, with its UJ3C series of 650 V SiC FETs.

Available in standard TO-220, TO-247 and D2PAK-3L packages, UnitedSiC says its silicon substitute operate with a standard Si-MOSFET gate drive. The hope is that it will eliminate the need to redesign drive circuits, while offering low RDS(ON) and low gate charge to reduce system losses.

The devices are said to be used for power factor correction and DC-DC conversion in both hard-switched and ZVS-switched systems.

The maximum drain current (ID) ratings for these SiC transistors is said to range from 31 amps to 85 amps. According to UnitedSiC, Low RDS(ON), specified at 27 milli-ohms, is best in class for TO-220 devices.

A built-in low Qrr body diode should also eliminate the need for an anti-parallel diode.

The UJ3C series are designed to be used in hard-switched converters and zero-voltage switching applications, such as LLC and phase-shifted full bridge converters.

The devices should also enable switching frequencies of up to 500kHz, which UnitedSiC believe will allow designers to reduce the size and cost of other system components.

UnitedSiC’s ‘simple silicon substitution’ technology comprises a patent-pending metal gate SiC JFET, co-packaged with a custom designed, ESD protected, low voltage silicon MOSFET.

UnitedSiC say that advanced proprietary die-attach and packaging techniques minimise losses and ensure effective thermal management. It explains that as a result, designers using silicon transistors in legacy designs can upgrade their existing system’s power performance using its plug-and-play devices.

Bethan Grylls