Evaluation of oscillatory phenomena in reverse operation for High Voltage Diodes

We have researched breaking the trade-off limitations between the overall loss and the reverse recovery softness of High Voltage (HV) freewheeling diodes. For the first time, our results show that the oscillatory phenomena in the reverse operation for HV diodes originate in the enlarging behavior of the space charge region to the cathode side during reverse operation and the extracting hole velocity at the end of the recovery period. The remaining hole of the cathode side affects the slowing and reduces the above behavior. We call this phenomenon the “relaxing electric field effect” at the cathode side. The novel HV diode structure can provide the necessary relaxing electric field effect for improving the soft recovery performance by employing the new Relaxed Field of Cathode (RFC) that utilizes LPT(II) technology. The RFC concept demonstrates a clear trade-off breakthrough between the overall loss and the reverse recovery softness of HV diodes.