Advanced RFC technology with new cathode structure of field limiting rings for High Voltage planar diode

Abstract

The edge of the active area and termination structure have a decisive influence on the recovery safety operating area (SOA) of High Voltage (HV) freewheeling diodes (FWDs). We have investigated the HV planar anode diode that breaks the triangle trade-off limitations between the overall loss, the reverse recovery softness and the recovery SOA. Our results show the destruction phenomena during the recovery operation for HV diodes originate in the local heating caused by high electric field and high current density at the end of the active area. Therefore, a newly developed HV diode based on the Relaxed Field of Cathode (RFC) technology achieves high total performance by adopting a new cathode structure of the field limiting rings region. The new diode offers low overall loss combined with a high recovery SOA and superior snap-off capability. The proposed new diode structure demonstrates a clear triangle trade-off breakthrough between the overall loss, the reverse softness and the recovery SOA of the HV diode.