Diode Evaluation and Series Diode Balancing for High-Voltage High-Frequency Power Converters

Miniaturization of high-voltage power converters is severely limited by the availability of fast switching, low-loss high-voltage diodes. This article explores techniques for using discrete low-voltage diodes in series as one high-voltage diode in high-frequency applications (e.g., hundreds of kHz and above). We identify that when series connecting diodes, the parasitic capacitance from the physical diode interconnections to common can result in voltage and temperature imbalance among the diodes, along with increased loss. We quantify the imbalance and propose two related compensation techniques. To validate the approaches, a full-bridge rectifier is tested with each branch consisting of four 3.3 kV SiC diodes in series. Experimental results showcase the imbalance and demonstrate the effectiveness of the compensation techniques. Additionally, we characterize the performance of a range of diodes for use in high-frequency, high-voltage converters. The proposed technique and evaluation results will be valuable for the design of lightweight and miniaturized high-voltage power converters.