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TMS320F28379D: SiC MOSFET aktive turn on during conducting phase of the body diode

Johannes Gloning
Prodigy 10 points
Part Number: TMS320F28379D

Tool/software:

Hello,

because the body diode in a SiC MOSFET has a high forward voltage compared to silicon parts, it generats more losses during switching and conduction. In opposite to an IGBT, a SiC MOSFET can conduct  reverse current from source to drain when supplied with a positive voltage at the gate. The SiC MOSFET in this condition has a much lower voltage drop from source to drain than the body diode. This can be used to lower the losses. (synchronous recifying, third quadrant operation?)

Is there an application note or an example in C2000 Ware, how this feature can be implemented into the TMS320F28379D or similar device in a 2-level inverter for motor control?
I think it should be a logical combination of current signum and the knowledge of the half bridge switching state. Is there a way to include this into the EPWM module or is an implementeation in the configurable logic block?

Best Regards,

Johannes

  • 0
    TI__Prodigy 340 points

    Hello Johannes,

    Sorry for the late response.

    Typically in a motor control application, the most widely used modulation schemes cause the switches in an inverter leg, half bridge, to switch complimentarily. Therefor any given time, except dead time, either of the FETs is on. Therefore, irrespective of the phase current direction, the current flows through the FET that is on and the motor phase sees the voltage corresponding to the on FET.

    Therefore, there isn't a special need for synchronous switching. That said, the body diode conducts during dead time and can increase losses in addition to reverse recovery loss when complimentary switch turns on. Since dead-time cannot be avoided, we can only optimize to improve the inverters efficiency.

    Hope this helps.

    Regards,

    Bhanu