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ISO5451: Desat for 3kV Bus

ReedKacz
Intellectual 2540 points
Part Number: ISO5451

Hi Team,

I have a need for a desat circuit when the collector of the IGBT is tied to a 3kV supply. The circuit is using 3x 1200V diodes in series, 1kOhm from the HV bus to DESAT pin. Also, the DESAT pin has a 12V TVS diode and a 1uF capacitor to secondary ground.

Does this setup seem correct? Any recommendation to improve this design?

Thanks,

Reed

  • 0
    TI__Expert 4875 points

    Hello Reed,

    With respect to voltage blocking, the series diodes sounds sufficient as long as you are expecting overvoltage below 3x1200V. Be aware that the series diodes and series resistor will cause the IGBT detection voltage to be reduced based on V_detect = 9V - (3*Vf + Rs*(0.5mA)). Where Vf is the forward voltage drop of the HV diode and Rs is the series resistor, 1kOhm. Also consider that your calculation for blanking time is also affected, where t_blank = (1uF)*V_detect / (0.5mA). The TVS diode voltage is good for protecting the pin. It is best to use diodes with small parasitic capacitance for the HV diodes and TVS protection diode.

    Regards,

    Audrey