Gate Driver Power Supply with Air-gapped Transformer for Medium Voltage Converters

In this paper, a gate driver power supply (GDPS) for SiC MOSFETs in medium-voltage power converters is presented. The main design considerations of the proposed GDPS are high voltage isolation, low coupling capacitance, and regulated output voltage. We present a design procedure for the transformer with an air gap to achieve the design objectives. Due to the air gap, the coupling factor of the proposed transformer is significantly lower than that of transformers without air gaps. Therefore, a series-series compensation network is designed to drive the loosely coupled magnetic link to achieve high-efficiency power transfer and stable output voltage. The input and output voltages of the proposed power supply are designed to be 24 VDC, and the rated output power is 20 W. The proposed transformer exceeds a partial discharge inception voltage of 20 kV RMS and has a coupling capacitance of 2.1 pF. The enclosure of the power supply is characterized by a creepage distance of 152 mm and a clearance distance of 80 mm between the input and output terminals of the GDPS. Compared with the commercially available high voltage gate driver power supply ISO5125I-120, the output power of the developed power supply is increased by four times, and the isolation strength doubled.