Grid-scale freewheeling diodes for HVDC transmission systems

Infineon Technologies Bipolar GmbH & Co. KG launches a new diode family especially designed for modern IGBT applications: Infineon Prime Soft. This diode features an improved turn-off capability which now rates at 5 kA/µs. Prime Soft builds on the well-received IGBT freewheeling diodes based on a monolithic silicon design. Typical applications for the diodes are HVDC/FACTs and medium voltage drives using voltage source converters. These applications are marked by demanding requirements on power losses.

Customers implementing the new Prime Soft diode profit from an industry leading low on-state loss. This is enabled by the monolithic silicon design creating an active silicon area increased by more than 25 percent compared to multichip diodes. This new design improves the switching power up to 6 to 10 MW at a maximum junction temperature of 140°C. Compared to a free-floating contact without solid metallurgical connection between silicon and molybdenum carrier, the thermal resistance of the new, bonded device is about 20 percent lower.

In addition to the high standards on reliability and good thermal properties, Infineon Prime Soft diodes feature minimum switching losses. Its soft reverse-recovery behavior shows no improper oscillations under all relevant operating conditions. Further to the electric parameters, the new mechanical concept simplifies the stack construction with series stacking of press-pack IGBTs and freewheeling diodes. This reduces the time needed for stack design by about 50 percent.

The ultra-soft IGBT freewheeling diodes in press-pack housings are available with 4.5 kV blocking voltage. The diodes come in three different silicon diameters: D1600U45X122, D2700U45X122, and D4600U45X172.