Controller IC Eases Design Of Quasi-Resonant AC-DC Converter Using SiC Power Switch

Focus:

Lacking a suitable controller chip for SiC MOSFETs, designers implementing ac-dc converter designs using SiC power MOSFETs are faced with challenges relating to power consumption and stability in a variety of high-power applications. To address these concerns, ROHM has developed an ac-dc converter controller (the BD768xFJ-LB) specifically for driving SiC MOSFETs. The performance of this new controller is demonstrated in a design presented here. In this example, the controller IC drives a SiC MOSFET in a three-phase, isolated flybuck quasi-resonant ac-dc converter with 300 to 900 Vdc in and 24 V output at 66 W max. After brief explanations of quasi-resonant operation and the controller’s features, implementation of the design example is discussed in detail including design of the transformer and selection of the SiC MOSFET and other components. Finally, the performance of the design is illustrated with graphs of efficiency and switching frequency vs load.

What you’ll learn:

• How to design a quasi resonant flybuck ac-dc converter using the BD768xFJ-LB controller and a SiC MOSFET
• How to design a SiC MOSFET based ac-dc converter

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Author & Publication:

Raimund Wagner and Walter Balzarotti, Rohm Semiconductor, Willich-Münchheide, Germany, How2Power Today, Oct 15 2015

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