Performance Improvement of Dual Active Bridge DC-DC Converter Using Cost-Effectiveness Si/SiC Hybrid Switch

IGBT or SiC devices are used in the high voltage side bridge of the dual active bridge (DAB) converters to sustain high voltage of kV range. However, the large hard switching turn-off loss of the IGBT restricts the maximum switching frequency and efficiency improvement of the DAB converter, while the much higher SiC material and fabrication cost results in a high cost/ampere ($/A) of SiC MOSFETs and hinders their widespread adoption in the market. In this paper, a costeffectiveness Si/SiC hybrid switch consisting of a high current Si IGBT and a low current SiC MOSFET is implemented in the bidirectional isolation dual active bridge (DAB) converter to achieve performance improvement without a significant cost penalty. Making use of the specific gate control pattern of the hybrid switch, the Si IGBT inside the hybrid switch could achieve the zero-voltage switching (ZVS) operation both at the turning-on and turning-off action, greatly reducing the total power loss of switching devices and increasing the switching frequency of the DAB converter. A hybrid modulation strategy of the hybrid switch is introduced into the DAB converter to eliminate the dual-side flow back currents and reduce the current stress of switching devices. The experimental results demonstrate that the Si/SiC hybrid switch based DAB converter can achieve 3% higher efficiency and 49 oC lower case temperature compared to the full IGBT solution at the same output power rating.